How do I create an Excel (.XLS and .XLSX) file in C# without installing Microsoft Office?

C#.NetExcelFile Io

C# Problem Overview


How can I create an Excel spreadsheet with C# without requiring Excel to be installed on the machine that's running the code?

C# Solutions


Solution 1 - C#

You can use a library called ExcelLibrary. It's a free, open source library posted on Google Code:

ExcelLibrary

This looks to be a port of the PHP ExcelWriter that you mentioned above. It will not write to the new .xlsx format yet, but they are working on adding that functionality in.

It's very simple, small and easy to use. Plus it has a DataSetHelper that lets you use DataSets and DataTables to easily work with Excel data.

ExcelLibrary seems to still only work for the older Excel format (.xls files), but may be adding support in the future for newer 2007/2010 formats.

You can also use EPPlus, which works only for Excel 2007/2010 format files (.xlsx files). There's also NPOI which works with both.

There are a few known bugs with each library as noted in the comments. In all, EPPlus seems to be the best choice as time goes on. It seems to be more actively updated and documented as well.

Also, as noted by @АртёмЦарионов below, EPPlus has support for Pivot Tables and ExcelLibrary may have some support (Pivot table issue in ExcelLibrary)

Here are a couple links for quick reference:
ExcelLibrary - GNU Lesser GPL
EPPlus - GNU (LGPL) - No longer maintained
EPPlus 5 - Polyform Noncommercial - Starting May 2020
NPOI - Apache License

Here some example code for ExcelLibrary:

Here is an example taking data from a database and creating a workbook from it. Note that the ExcelLibrary code is the single line at the bottom:

//Create the data set and table
DataSet ds = new DataSet("New_DataSet");
DataTable dt = new DataTable("New_DataTable");

//Set the locale for each
ds.Locale = System.Threading.Thread.CurrentThread.CurrentCulture;
dt.Locale = System.Threading.Thread.CurrentThread.CurrentCulture;

//Open a DB connection (in this example with OleDB)
OleDbConnection con = new OleDbConnection(dbConnectionString);
con.Open();

//Create a query and fill the data table with the data from the DB
string sql = "SELECT Whatever FROM MyDBTable;";
OleDbCommand cmd = new OleDbCommand(sql, con);
OleDbDataAdapter adptr = new OleDbDataAdapter();

adptr.SelectCommand = cmd;
adptr.Fill(dt);
con.Close();

//Add the table to the data set
ds.Tables.Add(dt);

//Here's the easy part. Create the Excel worksheet from the data set
ExcelLibrary.DataSetHelper.CreateWorkbook("MyExcelFile.xls", ds);

Creating the Excel file is as easy as that. You can also manually create Excel files, but the above functionality is what really impressed me.

Solution 2 - C#

If you are happy with the xlsx format, try my library, EPPlus. It started with the source from ExcelPackage, but since became a total rewrite.

It supports ranges, cell styling, charts, shapes, pictures, named ranges, AutoFilter, and a lot of other stuff.

You have two options:

  • EPPlus 4, licensed under LGPL (original branch, developed until 2020)

  • EPPlus 5, licensed under Polyform Noncommercial 1.0.0 (since 2020).

From the EPPlus 5 readme.md:

> With the new license EPPlus is still free to use in some cases, but will require a commercial license to be used in a commercial business.

EPPlus website: https://www.epplussoftware.com/

Solution 3 - C#

And what about using Open XML SDK 2.0 for Microsoft Office?

A few benefits:

  • Doesn't require Office installed
  • Made by Microsoft = decent MSDN documentation
  • Just one .Net dll to use in project
  • SDK comes with many tools like diff, validator, etc

Links:

Solution 4 - C#

I've used with success the following open source projects:

  • ExcelPackage for OOXML formats (Office 2007)

  • NPOI for .XLS format (Office 2003). NPOI 2.0 (Beta) also supports XLSX.

Take a look at my blog posts:

Creating Excel spreadsheets .XLS and .XLSX in C#

NPOI with Excel Table and dynamic Chart

Solution 5 - C#

You can use OLEDB to create and manipulate Excel files. Check this: Reading and Writing Excel using OLEDB.

Typical example:

using (OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\\temp\\test.xls;Extended Properties='Excel 8.0;HDR=Yes'"))
{
  conn.Open();
  OleDbCommand cmd = new OleDbCommand("CREATE TABLE [Sheet1] ([Column1] string, [Column2] string)", conn);
  cmd.ExecuteNonQuery();
}

EDIT - Some more links:

Solution 6 - C#

The commercial solution, SpreadsheetGear for .NET will do it.

You can see live ASP.NET (C# and VB) samples here and download an evaluation version here.

Disclaimer: I own SpreadsheetGear LLC

Solution 7 - C#

An extremely lightweight option may be to use HTML tables. Just create head, body, and table tags in a file, and save it as a file with an .xls extension. There are Microsoft specific attributes that you can use to style the output, including formulas.

I realize that you may not be coding this in a web application, but here is an example of the composition of an Excel file via an HTML table. This technique could be used if you were coding a console app, desktop app, or service.

Solution 8 - C#

A few options I have used:

If XLSX is a must: ExcelPackage is a good start but died off when the developer quit working on it. ExML picked up from there and added a few features. ExML isn't a bad option, I'm still using it in a couple of production websites.

For all of my new projects, though, I'm using NPOI, the .NET port of Apache POI. NPOI 2.0 (Alpha) also supports XLSX.

Solution 9 - C#

If you're creating Excel 2007/2010 files give this open source project a try: https://github.com/closedxml/closedxml

> It provides an object oriented way to manipulate the files (similar to > VBA) without dealing with the hassles of XML Documents. It can be used > by any .NET language like C# and Visual Basic (VB). > > ClosedXML allows you to create Excel 2007/2010 files without the Excel > application. The typical example is creating Excel reports on a web > server: > > var workbook = new XLWorkbook(); > var worksheet = workbook.Worksheets.Add("Sample Sheet"); > worksheet.Cell("A1").Value = "Hello World!"; > workbook.SaveAs("HelloWorld.xlsx");

Solution 10 - C#

You actually might want to check out the interop classes available in C# (e.g. Microsoft.Office.Interop.Excel. You say no OLE (which this isn't), but the interop classes are very easy to use. Check out the C# Documentation here (Interop for Excel starts on page 1072 of the C# PDF).

You might be impressed if you haven't tried them.

Please be warned of Microsoft's stance on this:

> Microsoft does not currently recommend, and does not support, > Automation of Microsoft Office applications from any unattended, > non-interactive client application or component (including ASP, > ASP.NET, DCOM, and NT Services), because Office may exhibit unstable > behavior and/or deadlock when Office is run in this environment.

Solution 11 - C#

You can use ExcelXmlWriter.

It works fine.

Solution 12 - C#

Here's a completely free C# library, which lets you export from a DataSet, DataTable or List<> into a genuine Excel 2007 .xlsx file, using the OpenXML libraries:

http://mikesknowledgebase.com/pages/CSharp/ExportToExcel.htm

Full source code is provided - free of charge - along with instructions, and a demo application.

After adding this class to your application, you can export your DataSet to Excel in just one line of code:

CreateExcelFile.CreateExcelDocument(myDataSet, "C:\\Sample.xlsx");

It doesn't get much simpler than that...

And it doesn't even require Excel to be present on your server.

Solution 13 - C#

You could consider creating your files using the XML Spreadsheet 2003 format. This is a simple XML format using a well documented schema.

Solution 14 - C#

You may want to take a look at GemBox.Spreadsheet.

They have a free version with all features but limited to 150 rows per sheet and 5 sheets per workbook, if that falls within your needs.

I haven't had need to use it myself yet, but does look interesting.

Solution 15 - C#

Syncfusion Essential XlsIO can do this. It has no dependency on Microsoft office and also has specific support for different platforms.

Code sample:

//Creates a new instance for ExcelEngine.
ExcelEngine excelEngine = new ExcelEngine();
//Loads or open an existing workbook through Open method of IWorkbooks
IWorkbook workbook = excelEngine.Excel.Workbooks.Open(fileName);
//To-Do some manipulation|
//To-Do some manipulation
//Set the version of the workbook.
workbook.Version = ExcelVersion.Excel2013;
//Save the workbook in file system as xlsx format
workbook.SaveAs(outputFileName);

The whole suite of controls is available for free through the community license program if you qualify (less than 1 million USD in revenue). Note: I work for Syncfusion.

Solution 16 - C#

The various Office 2003 XML libraries avaliable work pretty well for smaller excel files. However, I find the sheer size of a large workbook saved in the XML format to be a problem. For example, a workbook I work with that would be 40MB in the new (and admittedly more tightly packed) XLSX format becomes a 360MB XML file.

As far as my research has taken me, there are two commercial packages that allow output to the older binary file formats. They are:

Neither are cheap (500USD and 800USD respectively, I think). but both work independant of Excel itself.

What I would be curious about is the Excel output module for the likes of OpenOffice.org. I wonder if they can be ported from Java to .Net.

Solution 17 - C#

Well,

you can also use a third party library like Aspose.

This library has the benefit that it does not require Excel to be installed on your machine which would be ideal in your case.

Solution 18 - C#

I have written a simple code to export dataset to excel without using excel object by using System.IO.StreamWriter.

Below is the code which will read all tables from dataset and write them to sheets one by one. I took help from this article.

public static void exportToExcel(DataSet source, string fileName)
{
        const string endExcelXML = "</Workbook>";
        const string startExcelXML = "<xml version>\r\n<Workbook " +
                 "xmlns=\"urn:schemas-microsoft-com:office:spreadsheet\"\r\n" +
                 " xmlns:o=\"urn:schemas-microsoft-com:office:office\"\r\n " +
                 "xmlns:x=\"urn:schemas-    microsoft-com:office:" +
                 "excel\"\r\n xmlns:ss=\"urn:schemas-microsoft-com:" +
                 "office:spreadsheet\">\r\n <Styles>\r\n " +
                 "<Style ss:ID=\"Default\" ss:Name=\"Normal\">\r\n " +
                 "<Alignment ss:Vertical=\"Bottom\"/>\r\n <Borders/>" +
                 "\r\n <Font/>\r\n <Interior/>\r\n <NumberFormat/>" +
                 "\r\n <Protection/>\r\n </Style>\r\n " +
                 "<Style ss:ID=\"BoldColumn\">\r\n <Font " +
                 "x:Family=\"Swiss\" ss:Bold=\"1\"/>\r\n </Style>\r\n " +
                 "<Style     ss:ID=\"StringLiteral\">\r\n <NumberFormat" +
                 " ss:Format=\"@\"/>\r\n </Style>\r\n <Style " +
                 "ss:ID=\"Decimal\">\r\n <NumberFormat " +
                 "ss:Format=\"0.0000\"/>\r\n </Style>\r\n " +
                 "<Style ss:ID=\"Integer\">\r\n <NumberFormat " +
                 "ss:Format=\"0\"/>\r\n </Style>\r\n <Style " +
                 "ss:ID=\"DateLiteral\">\r\n <NumberFormat " +
                 "ss:Format=\"mm/dd/yyyy;@\"/>\r\n </Style>\r\n " +
                 "</Styles>\r\n ";
        System.IO.StreamWriter excelDoc = null;
        excelDoc = new System.IO.StreamWriter(fileName);

        int sheetCount = 1;
        excelDoc.Write(startExcelXML);
        foreach (DataTable table in source.Tables)
        {
            int rowCount = 0;
            excelDoc.Write("<Worksheet ss:Name=\"" + table.TableName + "\">");
            excelDoc.Write("<Table>");
            excelDoc.Write("<Row>");
            for (int x = 0; x < table.Columns.Count; x++)
            {
                excelDoc.Write("<Cell ss:StyleID=\"BoldColumn\"><Data ss:Type=\"String\">");
                excelDoc.Write(table.Columns[x].ColumnName);
                excelDoc.Write("</Data></Cell>");
            }
            excelDoc.Write("</Row>");
            foreach (DataRow x in table.Rows)
            {
                rowCount++;
                //if the number of rows is > 64000 create a new page to continue output
                if (rowCount == 64000)
                {
                    rowCount = 0;
                    sheetCount++;
                    excelDoc.Write("</Table>");
                    excelDoc.Write(" </Worksheet>");
                    excelDoc.Write("<Worksheet ss:Name=\"" + table.TableName + "\">");
                    excelDoc.Write("<Table>");
                }
                excelDoc.Write("<Row>"); //ID=" + rowCount + "
                for (int y = 0; y < table.Columns.Count; y++)
                {
                    System.Type rowType;
                    rowType = x[y].GetType();
                    switch (rowType.ToString())
                    {
                        case "System.String":
                            string XMLstring = x[y].ToString();
                            XMLstring = XMLstring.Trim();
                            XMLstring = XMLstring.Replace("&", "&");
                            XMLstring = XMLstring.Replace(">", ">");
                            XMLstring = XMLstring.Replace("<", "<");
                            excelDoc.Write("<Cell ss:StyleID=\"StringLiteral\">" +
                                           "<Data ss:Type=\"String\">");
                            excelDoc.Write(XMLstring);
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.DateTime":
                            //Excel has a specific Date Format of YYYY-MM-DD followed by  
                            //the letter 'T' then hh:mm:sss.lll Example 2005-01-31T24:01:21.000
                            //The Following Code puts the date stored in XMLDate 
                            //to the format above
                            DateTime XMLDate = (DateTime)x[y];
                            string XMLDatetoString = ""; //Excel Converted Date
                            XMLDatetoString = XMLDate.Year.ToString() +
                                 "-" +
                                 (XMLDate.Month < 10 ? "0" +
                                 XMLDate.Month.ToString() : XMLDate.Month.ToString()) +
                                 "-" +
                                 (XMLDate.Day < 10 ? "0" +
                                 XMLDate.Day.ToString() : XMLDate.Day.ToString()) +
                                 "T" +
                                 (XMLDate.Hour < 10 ? "0" +
                                 XMLDate.Hour.ToString() : XMLDate.Hour.ToString()) +
                                 ":" +
                                 (XMLDate.Minute < 10 ? "0" +
                                 XMLDate.Minute.ToString() : XMLDate.Minute.ToString()) +
                                 ":" +
                                 (XMLDate.Second < 10 ? "0" +
                                 XMLDate.Second.ToString() : XMLDate.Second.ToString()) +
                                 ".000";
                            excelDoc.Write("<Cell ss:StyleID=\"DateLiteral\">" +
                                         "<Data ss:Type=\"DateTime\">");
                            excelDoc.Write(XMLDatetoString);
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.Boolean":
                            excelDoc.Write("<Cell ss:StyleID=\"StringLiteral\">" +
                                        "<Data ss:Type=\"String\">");
                            excelDoc.Write(x[y].ToString());
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.Int16":
                        case "System.Int32":
                        case "System.Int64":
                        case "System.Byte":
                            excelDoc.Write("<Cell ss:StyleID=\"Integer\">" +
                                    "<Data ss:Type=\"Number\">");
                            excelDoc.Write(x[y].ToString());
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.Decimal":
                        case "System.Double":
                            excelDoc.Write("<Cell ss:StyleID=\"Decimal\">" +
                                  "<Data ss:Type=\"Number\">");
                            excelDoc.Write(x[y].ToString());
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.DBNull":
                            excelDoc.Write("<Cell ss:StyleID=\"StringLiteral\">" +
                                  "<Data ss:Type=\"String\">");
                            excelDoc.Write("");
                            excelDoc.Write("</Data></Cell>");
                            break;
                        default:
                            throw (new Exception(rowType.ToString() + " not handled."));
                    }
                }
                excelDoc.Write("</Row>");
            }
            excelDoc.Write("</Table>");
            excelDoc.Write(" </Worksheet>");
            sheetCount++;
        }


        excelDoc.Write(endExcelXML);
        excelDoc.Close();
    }

Solution 19 - C#

I've just recently used FlexCel.NET and found it to be an excellent library! I don't say that about too many software products. No point in giving the whole sales pitch here, you can read all the features on their website.

It is a commercial product, but you get the full source if you buy it. So I suppose you could compile it into your assembly if you really wanted to. Otherwise it's just one extra assembly to xcopy - no configuration or installation or anything like that.

I don't think you'll find any way to do this without third-party libraries as .NET framework, obviously, does not have built in support for it and OLE Automation is just a whole world of pain.

Solution 20 - C#

OpenXML is also a good alternative that helps avoid installing MS Excel on Server.The Open XML SDK 2.0 provided by Microsoft simplifies the task of manipulating Open XML packages and the underlying Open XML schema elements within a package. The Open XML Application Programming Interface (API) encapsulates many common tasks that developers perform on Open XML packages.

Check this out OpenXML: Alternative that helps avoid installing MS Excel on Server

Solution 21 - C#

I agree about generating XML Spreadsheets, here's an example on how to do it for C# 3 (everyone just blogs about it in VB 9 :P) http://www.aaron-powell.com/linq-to-xml-to-excel

Solution 22 - C#

Just want to add another reference to a third party solution that directly addresses your issue: http://www.officewriter.com

(Disclaimer: I work for SoftArtisans, the company that makes OfficeWriter)

Solution 23 - C#

public class GridViewExportUtil
{
    public static void Export(string fileName, GridView gv)
    {
        HttpContext.Current.Response.Clear();
        HttpContext.Current.Response.AddHeader(
            "content-disposition", string.Format("attachment; filename={0}", fileName));
        HttpContext.Current.Response.ContentType = "application/ms-excel";

        using (StringWriter sw = new StringWriter())
        {
            using (HtmlTextWriter htw = new HtmlTextWriter(sw))
            {
                //  Create a form to contain the grid
                Table table = new Table();

                //  add the header row to the table
                if (gv.HeaderRow != null)
                {
                    GridViewExportUtil.PrepareControlForExport(gv.HeaderRow);
                    table.Rows.Add(gv.HeaderRow);
                }

                //  add each of the data rows to the table
                foreach (GridViewRow row in gv.Rows)
                {
                    GridViewExportUtil.PrepareControlForExport(row);
                    table.Rows.Add(row);
                }

                //  add the footer row to the table
                if (gv.FooterRow != null)
                {
                    GridViewExportUtil.PrepareControlForExport(gv.FooterRow);
                    table.Rows.Add(gv.FooterRow);
                }

                //  render the table into the htmlwriter
                table.RenderControl(htw);

                //  render the htmlwriter into the response
                HttpContext.Current.Response.Write(sw.ToString());
                HttpContext.Current.Response.End();
            }
        }
    }

    /// <summary>
    /// Replace any of the contained controls with literals
    /// </summary>
    /// <param name="control"></param>
    private static void PrepareControlForExport(Control control)
    {
        for (int i = 0; i < control.Controls.Count; i++)
        {
            Control current = control.Controls[i];
            if (current is LinkButton)
            {
                control.Controls.Remove(current);
                control.Controls.AddAt(i, new LiteralControl((current as LinkButton).Text));
            }
            else if (current is ImageButton)
            {
                control.Controls.Remove(current);
                control.Controls.AddAt(i, new LiteralControl((current as ImageButton).AlternateText));
            }
            else if (current is HyperLink)
            {
                control.Controls.Remove(current);
                control.Controls.AddAt(i, new LiteralControl((current as HyperLink).Text));
            }
            else if (current is DropDownList)
            {
                control.Controls.Remove(current);
                control.Controls.AddAt(i, new LiteralControl((current as DropDownList).SelectedItem.Text));
            }
            else if (current is CheckBox)
            {
                control.Controls.Remove(current);
                control.Controls.AddAt(i, new LiteralControl((current as CheckBox).Checked ? "True" : "False"));
            }

            if (current.HasControls())
            {
                GridViewExportUtil.PrepareControlForExport(current);
            }
        }
    }
}

Hi this solution is to export your grid view to your excel file it might help you out

Solution 24 - C#

IKVM + POI

Or, you could use the Interop ...

Solution 25 - C#

Here's a way to do it with LINQ to XML, complete with sample code:

Quickly Import and Export Excel Data with LINQ to XML

It's a little complex, since you have to import namespaces and so forth, but it does let you avoid any external dependencies.

(Also, of course, it's VB .NET, not C#, but you can always isolate the VB .NET stuff in its own project to use XML Literals, and do everything else in C#.)

Solution 26 - C#

You can create nicely formatted Excel files using this library: http://officehelper.codeplex.com/documentation
See below sample:

using (ExcelHelper helper = new ExcelHelper(TEMPLATE_FILE_NAME, GENERATED_FILE_NAME))
{
    helper.Direction = ExcelHelper.DirectionType.TOP_TO_DOWN;
    helper.CurrentSheetName = "Sheet1";
    helper.CurrentPosition = new CellRef("C3");

    //the template xlsx should contains the named range "header"; use the command "insert"/"name".
    helper.InsertRange("header");

    //the template xlsx should contains the named range "sample1";
    //inside this range you should have cells with these values:
    //<name> , <value> and <comment>, which will be replaced by the values from the getSample()
    CellRangeTemplate sample1 = helper.CreateCellRangeTemplate("sample1", new List<string> {"name", "value", "comment"}); 
    helper.InsertRange(sample1, getSample());
            
    //you could use here other named ranges to insert new cells and call InsertRange as many times you want, 
    //it will be copied one after another;
    //even you can change direction or the current cell/sheet before you insert
            
    //typically you put all your "template ranges" (the names) on the same sheet and then you just delete it
    helper.DeleteSheet("Sheet3");
}        

where sample look like this:

private IEnumerable<List<object>> getSample()
{
    var random = new Random();
        
    for (int loop = 0; loop < 3000; loop++)
    {
        yield return new List<object> {"test", DateTime.Now.AddDays(random.NextDouble()*100 - 50), loop};
    }
}

Solution 27 - C#

Some 3rd party component vendors like Infragistics or Syncfusion provide very good Excel export capabilities that do not require Microsoft Excel to be installed.

Since these vendors also provide advanced UI grid components, these components are particularly handy if you want the style and layout of an excel export to mimic the current state of a grid in the user interface of your application.

If your export is intended to be executed server side with emphasis on the data to be exported and with no link to the UI, then I would go for one of the free open source options (e.g. ExcelLibrary).

I have previously been involved with projects that attempted to use server side automation on the Microsoft Office suite. Based on this experience I would strongly recommend against that approach.

Solution 28 - C#

The simplest and fastest way to create an Excel file from C# is to use the Open XML Productivity Tool. The Open XML Productivity Tool comes with the Open XML SDK installation. The tool reverse engineers any Excel file into C# code. The C# code can then be used to re-generate that file.

An overview of the process involved is:

  1. Install the Open XML SDK with the tool.
  2. Create an Excel file using the latest Excel client with desired look. Name it DesiredLook.xlsx.
  3. With the tool open DesiredLook.xlsx and click the Reflect Code button near the top. enter image description here
  4. The C# code for your file will be generated in the right pane of the tool. Add this to your C# solution and generate files with that desired look.

As a bonus, this method works for any Word and PowerPoint files. As the C# developer, you will then make changes to the code to fit your needs.

I have developed a simple WPF app on github which will run on Windows for this purpose. There is a placeholder class called GeneratedClass where you can paste the generated code. If you go back one version of the file, it will generate an excel file like this:

enter image description here

Solution 29 - C#

The Java open source solution is Apache POI. Maybe there is a way to setup interop here, but I don't know enough about Java to answer that.

When I explored this problem I ended up using the Interop assemblies.

Solution 30 - C#

Have you ever tried sylk?

We used to generate excelsheets in classic asp as sylk and right now we're searching for an excelgenerater too.

The advantages for sylk are, you can format the cells.

Solution 31 - C#

You can just write it out to XML using the Excel XML format and name it with .XLS extension and it will open with excel. You can control all the formatting (bold, widths, etc) in your XML file heading.

There is an example XML from Wikipedia.

Solution 32 - C#

I also vote for GemBox.Spreadsheet.

Very fast and easy to use, with tons of examples on their site.

Took my reporting tasks on a whole new level of execution speed.

Solution 33 - C#

One really easy option which is often overlooked is to create a .rdlc report using Microsoft Reporting and export it to excel format. You can design it in visual studio and generate the file using:

localReport.Render("EXCELOPENXML", null, ((name, ext, encoding, mimeType, willSeek) => stream = new FileStream(name, FileMode.CreateNew)), out warnings);

You can also export it do .doc or .pdf, using "WORDOPENXML" and "PDF" respectively, and it's supported on many different platforms such as ASP.NET and SSRS.

It's much easier to make changes in a visual designer where you can see the results, and trust me, once you start grouping data, formatting group headers, adding new sections, you don't want to mess with dozens of XML nodes.

Solution 34 - C#

You can try my SwiftExcel library. This library writes directly to the file, so it is very efficient. For example you can write 100k rows in few seconds without any memory usage.

Here is a simple example of usage:

using (var ew = new ExcelWriter("C:\\temp\\test.xlsx"))
{
    for (var row = 1; row <= 10; row++)
    {
        for (var col = 1; col <= 5; col++)
        {
            ew.Write($"row:{row}-col:{col}", col, row);
        }
    }
}

Solution 35 - C#

http://www.codeproject.com/KB/cs/Excel_and_C_.aspx <= why not just use the built in power of windows, just install office on the server, any application that you install can be automated.

So much easier just use the native methods.

If it installed you can use it, this is the most awesome and under used feature in windows it was Dubbed COM back in the good old days, and it saves you tons of time and pain.

Or even easier just use the ref lib MS supplies - http://csharp.net-informations.com/excel/csharp-create-excel.htm

Solution 36 - C#

How to create an Excel (.xslx) file using C# on OneDrive without installing Microsoft Office

The Microsoft Graph API provides File and Excel APIs for creating and modifying Excel files stored in OneDrive for both enterprise and consumer accounts. The Microsoft.Graph NuGet package provides many interfaces for working with the File and Excel APIs.

{
  Name = "myExcelFile.xslx",
  File = new Microsoft.Graph.File()
};

// Create an empty file in the user's OneDrive.
var excelWorkbookDriveItem = await graphClient.Me.Drive.Root.Children.Request().AddAsync(excelWorkbook);

// Add the contents of a template Excel file.
DriveItem excelDriveItem;
using (Stream ms = ResourceHelper.GetResourceAsStream(ResourceHelper.ExcelTestResource))
{
    //Upload content to the file. ExcelTestResource is an empty template Excel file.
    //https://graph.microsoft.io/en-us/docs/api-reference/v1.0/api/item_uploadcontent
    excelDriveItem = await graphClient.Me.Drive.Items[excelWorkbookDriveItem.Id].Content.Request().PutAsync<DriveItem>(ms);
}

At this point, you now have an Excel file created in the user (enterprise or consumer) or group's OneDrive. You can now use the Excel APIs to make changes to the Excel file without using Excel and without needing to understand the Excel XML format.

Solution 37 - C#

I recode again the code and now you can create an .xls file, later you can convert to Excel 2003 Open XML Format.

private static void exportToExcel(DataSet source, string fileName)
    {
        // Documentacion en:
        // https://en.wikipedia.org/wiki/Microsoft_Office_XML_formats
        // https://answers.microsoft.com/en-us/msoffice/forum/all/how-to-save-office-ms-xml-as-xlsx-file/4a77dae5-6855-457d-8359-e7b537beb1db
        // https://riptutorial.com/es/openxml

        const string startExcelXML = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\r\n"+
                 "<?mso-application progid=\"Excel.Sheet\"?>\r\n" +
                 "<Workbook xmlns=\"urn:schemas-microsoft-com:office:spreadsheet\"\r\n" +
                 "xmlns:o=\"urn:schemas-microsoft-com:office:office\"\r\n " +
                 "xmlns:x=\"urn:schemas-microsoft-com:office:excel\"\r\n " +
                 "xmlns:ss=\"urn:schemas-microsoft-com:office:spreadsheet\"\r\n " +
                 "xmlns:html=\"http://www.w3.org/TR/REC-html40\">\r\n " +
                 "xmlns:html=\"https://www.w3.org/TR/html401/\">\r\n " +

                 "<DocumentProperties xmlns=\"urn:schemas-microsoft-com:office:office\">\r\n " +
                 "  <Version>16.00</Version>\r\n " +
                 "</DocumentProperties>\r\n " +
                 " <OfficeDocumentSettings xmlns=\"urn:schemas-microsoft-com:office:office\">\r\n " +
                 "  <AllowPNG/>\r\n " +
                 " </OfficeDocumentSettings>\r\n " +

                 " <ExcelWorkbook xmlns=\"urn:schemas-microsoft-com:office:excel\">\r\n " +
                 "  <WindowHeight>9750</WindowHeight>\r\n " +
                 "  <WindowWidth>24000</WindowWidth>\r\n " +
                 "  <WindowTopX>0</WindowTopX>\r\n " +
                 "  <WindowTopY>0</WindowTopY>\r\n " +
                 "  <RefModeR1C1/>\r\n " +
                 "  <ProtectStructure>False</ProtectStructure>\r\n " +
                 "  <ProtectWindows>False</ProtectWindows>\r\n " +
                 " </ExcelWorkbook>\r\n " +

                 "<Styles>\r\n " +
                 "<Style ss:ID=\"Default\" ss:Name=\"Normal\">\r\n " +
                 "<Alignment ss:Vertical=\"Bottom\"/>\r\n <Borders/>" +
                 "\r\n <Font/>\r\n <Interior/>\r\n <NumberFormat/>" +
                 "\r\n <Protection/>\r\n </Style>\r\n " +
                 "<Style ss:ID=\"BoldColumn\">\r\n <Font " +
                 "x:Family=\"Swiss\" ss:Bold=\"1\"/>\r\n </Style>\r\n " +
                 "<Style ss:ID=\"StringLiteral\">\r\n <NumberFormat" +
                 " ss:Format=\"@\"/>\r\n </Style>\r\n <Style " +
                 "ss:ID=\"Decimal\">\r\n <NumberFormat " +
                 "ss:Format=\"0.0000\"/>\r\n </Style>\r\n " +
                 "<Style ss:ID=\"Integer\">\r\n <NumberFormat/>" +
                 "ss:Format=\"0\"/>\r\n </Style>\r\n <Style " +
                 "ss:ID=\"DateLiteral\">\r\n <NumberFormat " +
                 "ss:Format=\"dd/mm/yyyy;@\"/>\r\n </Style>\r\n " +
                 "</Styles>\r\n ";
        System.IO.StreamWriter excelDoc = null;
        excelDoc = new System.IO.StreamWriter(fileName,false);

        int sheetCount = 1;
        excelDoc.Write(startExcelXML);
        foreach (DataTable table in source.Tables)
        {
            int rowCount = 0;
            excelDoc.Write("<Worksheet ss:Name=\"" + table.TableName + "\">");
            excelDoc.Write("<Table>");
            excelDoc.Write("<Row>");
            for (int x = 0; x < table.Columns.Count; x++)
            {
                excelDoc.Write("<Cell ss:StyleID=\"BoldColumn\"><Data ss:Type=\"String\">");
                excelDoc.Write(table.Columns[x].ColumnName);
                excelDoc.Write("</Data></Cell>");
            }
            excelDoc.Write("</Row>");
            foreach (DataRow x in table.Rows)
            {
                rowCount++;
                //if the number of rows is > 64000 create a new page to continue output
                if (rowCount == 1048576)
                {
                    rowCount = 0;
                    sheetCount++;
                    excelDoc.Write("</Table>");
                    excelDoc.Write(" </Worksheet>");
                    excelDoc.Write("<Worksheet ss:Name=\"" + table.TableName + "\">");
                    excelDoc.Write("<Table>");
                }
                excelDoc.Write("<Row>"); //ID=" + rowCount + "
                for (int y = 0; y < table.Columns.Count; y++)
                {
                    System.Type rowType;
                    rowType = x[y].GetType();
                    switch (rowType.ToString())
                    {
                        case "System.String":
                            string XMLstring = x[y].ToString();
                            XMLstring = XMLstring.Trim();
                            XMLstring = XMLstring.Replace("&", "&");
                            XMLstring = XMLstring.Replace(">", ">");
                            XMLstring = XMLstring.Replace("<", "<");
                            excelDoc.Write("<Cell ss:StyleID=\"StringLiteral\">" +
                                           "<Data ss:Type=\"String\">");
                            excelDoc.Write(XMLstring);
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.DateTime":
                            //Excel has a specific Date Format of YYYY-MM-DD followed by  
                            //the letter 'T' then hh:mm:sss.lll Example 2005-01-31T24:01:21.000
                            //The Following Code puts the date stored in XMLDate 
                            //to the format above
                            DateTime XMLDate = (DateTime)x[y];
                            string XMLDatetoString = ""; //Excel Converted Date
                            XMLDatetoString = XMLDate.Year.ToString() +
                                 "-" +
                                 (XMLDate.Month < 10 ? "0" +
                                 XMLDate.Month.ToString() : XMLDate.Month.ToString()) +
                                 "-" +
                                 (XMLDate.Day < 10 ? "0" +
                                 XMLDate.Day.ToString() : XMLDate.Day.ToString()) +
                                 "T" +
                                 (XMLDate.Hour < 10 ? "0" +
                                 XMLDate.Hour.ToString() : XMLDate.Hour.ToString()) +
                                 ":" +
                                 (XMLDate.Minute < 10 ? "0" +
                                 XMLDate.Minute.ToString() : XMLDate.Minute.ToString()) +
                                 ":" +
                                 (XMLDate.Second < 10 ? "0" +
                                 XMLDate.Second.ToString() : XMLDate.Second.ToString()) +
                                 ".000";
                            excelDoc.Write("<Cell ss:StyleID=\"DateLiteral\">" +
                                         "<Data ss:Type=\"DateTime\">");
                            excelDoc.Write(XMLDatetoString);
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.Boolean":
                            excelDoc.Write("<Cell ss:StyleID=\"StringLiteral\">" +
                                        "<Data ss:Type=\"String\">");
                            excelDoc.Write(x[y].ToString());
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.Int16":
                        case "System.Int32":
                        case "System.Int64":
                        case "System.Byte":
                            excelDoc.Write("<Cell ss:StyleID=\"Integer\">" +
                                    "<Data ss:Type=\"Number\">");
                            excelDoc.Write(x[y].ToString());
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.Decimal":
                        case "System.Double":
                            excelDoc.Write("<Cell ss:StyleID=\"Decimal\">" +
                                  "<Data ss:Type=\"Number\">");
                            excelDoc.Write(x[y].ToString());
                            excelDoc.Write("</Data></Cell>");
                            break;
                        case "System.DBNull":
                            excelDoc.Write("<Cell ss:StyleID=\"StringLiteral\">" +
                                  "<Data ss:Type=\"String\">");
                            excelDoc.Write("");
                            excelDoc.Write("</Data></Cell>");
                            break;
                        default:
                            throw (new Exception(rowType.ToString() + " not handled."));
                    }
                }
                excelDoc.Write("</Row>");
            }
            excelDoc.Write("</Table>");
            excelDoc.Write("</Worksheet>");               
            sheetCount++;
        }

        const string endExcelOptions1 = "\r\n<WorksheetOptions xmlns=\"urn:schemas-microsoft-com:office:excel\">\r\n" +
            "<Selected/>\r\n" +
            "<ProtectObjects>False</ProtectObjects>\r\n" +
            "<ProtectScenarios>False</ProtectScenarios>\r\n" +
            "</WorksheetOptions>\r\n";

        excelDoc.Write(endExcelOptions1);
        excelDoc.Write("</Workbook>");
        excelDoc.Close();
    }

Solution 38 - C#

You can install OpenXml nuget package on Visual Studio. Here is a bit of code to export a data table to an excel file:

Imports DocumentFormat.OpenXml
Imports DocumentFormat.OpenXml.Packaging
Imports DocumentFormat.OpenXml.Spreadsheet

Public Class ExportExcelClass
    Public Sub New()

    End Sub

    Public Sub ExportDataTable(ByVal table As DataTable, ByVal exportFile As String)
        ' Create a spreadsheet document by supplying the filepath.
        ' By default, AutoSave = true, Editable = true, and Type = xlsx.
        Dim spreadsheetDocument As SpreadsheetDocument = spreadsheetDocument.Create(exportFile, SpreadsheetDocumentType.Workbook)

        ' Add a WorkbookPart to the document.
        Dim workbook As WorkbookPart = spreadsheetDocument.AddWorkbookPart
        workbook.Workbook = New Workbook

        ' Add a WorksheetPart to the WorkbookPart.
        Dim Worksheet As WorksheetPart = workbook.AddNewPart(Of WorksheetPart)()
        Worksheet.Worksheet = New Worksheet(New SheetData())

        ' Add Sheets to the Workbook.
        Dim sheets As Sheets = spreadsheetDocument.WorkbookPart.Workbook.AppendChild(Of Sheets)(New Sheets())

        Dim data As SheetData = Worksheet.Worksheet.GetFirstChild(Of SheetData)()
        Dim Header As Row = New Row()
        Header.RowIndex = CType(1, UInt32)

        For Each column As DataColumn In table.Columns
            Dim headerCell As Cell = createTextCell(table.Columns.IndexOf(column) + 1, 1, column.ColumnName)
            Header.AppendChild(headerCell)
        Next

        data.AppendChild(Header)

        Dim contentRow As DataRow
        For i As Integer = 0 To table.Rows.Count - 1
            contentRow = table.Rows(i)
            data.AppendChild(createContentRow(contentRow, i + 2))
        Next

    End Sub

    Private Function createTextCell(ByVal columnIndex As Integer, ByVal rowIndex As Integer, ByVal cellValue As Object) As Cell
        Dim cell As Cell = New Cell()
        cell.DataType = CellValues.InlineString

        cell.CellReference = getColumnName(columnIndex) + rowIndex.ToString

        Dim inlineString As InlineString = New InlineString()
        Dim t As Text = New Text()
        t.Text = cellValue.ToString()
        inlineString.AppendChild(t)
        cell.AppendChild(inlineString)
        Return cell
    End Function

    Private Function createContentRow(ByVal dataRow As DataRow, ByVal rowIndex As Integer) As Row
        Dim row As Row = New Row With {
            .rowIndex = CType(rowIndex, UInt32)
        }

        For i As Integer = 0 To dataRow.Table.Columns.Count - 1
            Dim dataCell As Cell = createTextCell(i + 1, rowIndex, dataRow(i))
            row.AppendChild(dataCell)
        Next

        Return row
    End Function

    Private Function getColumnName(ByVal columnIndex As Integer) As String
        Dim dividend As Integer = columnIndex
        Dim columnName As String = String.Empty
        Dim modifier As Integer

        While dividend > 0
            modifier = (dividend - 1) Mod 26
            columnName = Convert.ToChar(65 + modifier).ToString() & columnName
            dividend = CInt(((dividend - modifier) / 26))
        End While

        Return columnName
    End Function
End Class

Solution 39 - C#

If you make data table or datagridview from the code you can save all data using this simple method.this method not recomended but its working 100%, even you are not install MS Excel in your computer.

try
 {
  SaveFileDialog saveFileDialog1 = new SaveFileDialog();
  saveFileDialog1.Filter = "Excel Documents (*.xls)|*.xls";
  saveFileDialog1.FileName = "Employee Details.xls";
  if (saveFileDialog1.ShowDialog() == DialogResult.OK)
  {
  string fname = saveFileDialog1.FileName;
  StreamWriter wr = new StreamWriter(fname);
  for (int i = 0; i <DataTable.Columns.Count; i++)
  {
  wr.Write(DataTable.Columns[i].ToString().ToUpper() + "\t");
  }
  wr.WriteLine();

  //write rows to excel file
  for (int i = 0; i < (DataTable.Rows.Count); i++)
  {
  for (int j = 0; j < DataTable.Columns.Count; j++)
  {
  if (DataTable.Rows[i][j] != null)
  {
  wr.Write(Convert.ToString(getallData.Rows[i][j]) + "\t");
  }
   else
   {
   wr.Write("\t");
   }
   }
   //go to next line
   wr.WriteLine();
   }
   //close file
   wr.Close();
   }
   }
   catch (Exception)
   {
    MessageBox.Show("Error Create Excel Sheet!");
   }

Solution 40 - C#

Some time ago, I created a DLL on top of NPOI. It's very simple to use it:

IList<DummyPerson> dummyPeople = new List<DummyPerson>();
//Add data to dummyPeople...
IExportEngine engine = new ExcelExportEngine();
engine.AddData(dummyPeople); 
MemoryStream memory = engine.Export();

You could read more about it on here.

By the way, is 100% open source. Feel free to use, edit and share ;)

Solution 41 - C#

To save xls into xlsx format, we just need to call SaveAs method from Microsoft.Office.Interop.Excel library. This method will take around 16 parameters and one of them is file format as well.

Microsoft document: Here SaveAs Method Arguments

The object we need to pass is like

wb.SaveAs(filename, 51, System.Reflection.Missing.Value,
System.Reflection.Missing.Value, false, false, 1,1, true, 
System.Reflection.Missing.Value, System.Reflection.Missing.Value, System.Reflection.Missing.Value)

Here, 51 is is enumeration value for XLSX

For SaveAs in different file formats you can refer the xlFileFormat

Solution 42 - C#

I wonder why nobody suggested PowerShell with the free ImportExcel Module; it creates XML-Excel files (xlsx) with ease.

Especially easy when creating Excel-sheets coming from Databases like SQL Server...

Solution 43 - C#

In my projects, I use some several .net libraries to extract Excel File (both .xls and .xlsx)

To Export data, I frequently use rdlc.

To modify excel files I use (Sample code when I try to set blank Cell A15):

ClosedXML

        //Closed XML
        var workbook = new XLWorkbook(sUrlFile); // load the existing excel file
        var worksheet = workbook.Worksheets.Worksheet(1);
        worksheet.Cell("A15").SetValue("");
        workbook.Save();

IronXL

       string sUrlFile = "G:\\ReportAmortizedDetail.xls";
        WorkBook workbook = WorkBook.Load(sUrlFile);
        WorkSheet sheet = workbook.WorkSheets.First();
        //Select cells easily in Excel notation and return the calculated value
        sheet["A15"].First().Value = "";
        sheet["A15"].First().FormatString = "";

        workbook.Save();
        workbook.Close();
        workbook = null;

SpireXLS (When I try, the library print additional sheet to give information that we use the trial library

            string sUrlFile = "G:\\ReportAmortizedDetail.xls";
            Workbook workbook = new Workbook();
            workbook.LoadFromFile(sUrlFile);
            //Get the 1st sheet
            Worksheet sheet = workbook.Worksheets[0];
            //Specify the cell range
            CellRange range = sheet.Range["A15"];
            //Find all matched text in the range
            CellRange[] cells = range.FindAllString("hi", false, false);
            //Replace text
            foreach (CellRange cell in range)
            {
                cell.Text = "";
            }
            //Save
            workbook.Save();

Jet Oledb

    //ExcelTool Class
    public static int ExcelUpdateSheets(string path, string sWorksheetName, string sCellLocation, string sValue)
    {
        int iResult = -99;
        String sConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + path + ";Extended Properties='Excel 8.0;HDR=NO'";
        OleDbConnection objConn = new OleDbConnection(sConnectionString);
        objConn.Open();
        OleDbCommand objCmdSelect = new OleDbCommand("UPDATE [" + sWorksheetName + "$" + sCellLocation + "] SET F1=" + UtilityClass.ValueSQL(sValue), objConn);
        objCmdSelect.ExecuteNonQuery();
        objConn.Close();

        return iResult;
    }

Usage :

    ExcelTool.ExcelUpdateSheets(sUrlFile, "ReportAmortizedDetail", "A15:A15", "");

Aspose

            var workbook = new Aspose.Cells.Workbook(sUrlFile);
            // access first (default) worksheet
            var sheet = workbook.Worksheets[0];
            // access CellsCollection of first worksheet
            var cells = sheet.Cells;
            // write HelloWorld to cells A1
            cells["A15"].Value = "";
            // save spreadsheet to disc
            workbook.Save(sUrlFile);
            workbook.Dispose();
            workbook = null;

Solution 44 - C#

Here is the simplest way to create an Excel file.

Excel files with extension .xlsx are compressed folders containing .XML files - but complicated.

First create the folder structure as follows -

public class CreateFileOrFolder
{
    static void Main()
    {
        //
        // https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/file-system/how-to-create-a-file-or-folder
        //
        // https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/file-system/how-to-write-to-a-text-file
        //
        // .NET Framework 4.7.2
        //
        // Specify a name for your top-level folder.
        string folderName = @"C:\Users\david\Desktop\Book3";

        // To create a string that specifies the path to a subfolder under your
        // top-level folder, add a name for the subfolder to folderName.

        string pathString = System.IO.Path.Combine(folderName, "_rels");
        System.IO.Directory.CreateDirectory(pathString);
        pathString = System.IO.Path.Combine(folderName, "docProps");
        System.IO.Directory.CreateDirectory(pathString);
        pathString = System.IO.Path.Combine(folderName, "xl");
        System.IO.Directory.CreateDirectory(pathString);

        string subPathString = System.IO.Path.Combine(pathString, "_rels");
        System.IO.Directory.CreateDirectory(subPathString);
        subPathString = System.IO.Path.Combine(pathString, "theme");
        System.IO.Directory.CreateDirectory(subPathString);
        subPathString = System.IO.Path.Combine(pathString, "worksheets");
        System.IO.Directory.CreateDirectory(subPathString);
        // Keep the console window open in debug mode.
        System.Console.WriteLine("Press any key to exit.");
        System.Console.ReadKey();
    }
}

Next, create text files to hold the XML needed to describe the Excel spreadsheet.

namespace MakeFiles3
{
    class Program
    {
        static void Main(string[] args)
        {
            //
            // https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/file-system/how-to-write-to-a-text-file
            //
            // .NET Framework 4.7.2
            //
            string fileName = @"C:\Users\david\Desktop\Book3\_rels\.rels";
            fnWriteFile(fileName);
            fileName = @"C:\Users\david\Desktop\Book3\docProps\app.xml";
            fnWriteFile(fileName);
            fileName = @"C:\Users\david\Desktop\Book3\docProps\core.xml";
            fnWriteFile(fileName);
            fileName = @"C:\Users\david\Desktop\Book3\xl\_rels\workbook.xml.rels";
            fnWriteFile(fileName);
            fileName = @"C:\Users\david\Desktop\Book3\xl\theme\theme1.xml";
            fnWriteFile(fileName);
            fileName = @"C:\Users\david\Desktop\Book3\xl\worksheets\sheet1.xml";
            fnWriteFile(fileName);
            fileName = @"C:\Users\david\Desktop\Book3\xl\styles.xml";
            fnWriteFile(fileName);
            fileName = @"C:\Users\david\Desktop\Book3\xl\workbook.xml";
            fnWriteFile(fileName);
            fileName = @"C:\Users\david\Desktop\Book3\[Content_Types].xml";
            fnWriteFile(fileName);
            // Keep the console window open in debug mode.
            System.Console.WriteLine("Press any key to exit.");
            System.Console.ReadKey();

            bool fnWriteFile(string strFilePath)
            {
                if (!System.IO.File.Exists(strFilePath))
                {
                    using (System.IO.FileStream fs = System.IO.File.Create(strFilePath))
                    {
                        return true;
                    }
                }
                else
                {
                    System.Console.WriteLine("File \"{0}\" already exists.", strFilePath);
                    return false;
                }
            }
        }
    }
}

Next populate the text files with XML.

The XML required is fairly verbose so you may need to use this github repository.

https://github.com/DaveTallett26/MakeFiles4/blob/master/MakeFiles4/Program.cs

//
// https://docs.microsoft.com/en-us/dotnet/standard/io/how-to-write-text-to-a-file
// .NET Framework 4.7.2
//
using System.IO;

namespace MakeFiles4
{
    class Program
    {
        static void Main(string[] args)
        {
            string xContents = @"a";
            string xFilename = @"a";
            xFilename = @"C:\Users\david\Desktop\Book3\[Content_Types].xml";
            xContents = @"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?><Types xmlns=""http://schemas.openxmlformats.org/package/2006/content-types""><Default Extension=""rels"" ContentType=""application/vnd.openxmlformats-package.relationships+xml""/><Default Extension=""xml"" ContentType=""application/xml""/><Override PartName=""/xl/workbook.xml"" ContentType=""application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml""/><Override PartName=""/xl/worksheets/sheet1.xml"" ContentType=""application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml""/><Override PartName=""/xl/theme/theme1.xml"" ContentType=""application/vnd.openxmlformats-officedocument.theme+xml""/><Override PartName=""/xl/styles.xml"" ContentType=""application/vnd.openxmlformats-officedocument.spreadsheetml.styles+xml""/><Override PartName=""/docProps/core.xml"" ContentType=""application/vnd.openxmlformats-package.core-properties+xml""/><Override PartName=""/docProps/app.xml"" ContentType=""application/vnd.openxmlformats-officedocument.extended-properties+xml""/></Types>";
            StartExstream(xContents, xFilename);

            xFilename = @"C:\Users\david\Desktop\Book3\_rels\.rels";
            xContents = @"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?><Relationships xmlns=""http://schemas.openxmlformats.org/package/2006/relationships""><Relationship Id=""rId3"" Type=""http://schemas.openxmlformats.org/officeDocument/2006/relationships/extended-properties"" Target=""docProps/app.xml""/><Relationship Id=""rId2"" Type=""http://schemas.openxmlformats.org/package/2006/relationships/metadata/core-properties"" Target=""docProps/core.xml""/><Relationship Id=""rId1"" Type=""http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument"" Target=""xl/workbook.xml""/></Relationships>";
            StartExstream(xContents, xFilename);

            xFilename = @"C:\Users\david\Desktop\Book3\docProps\app.xml";
            xContents = @"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?><Properties xmlns=""http://schemas.openxmlformats.org/officeDocument/2006/extended-properties"" xmlns:vt=""http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes""><Application>Microsoft Excel</Application><DocSecurity>0</DocSecurity><ScaleCrop>false</ScaleCrop><HeadingPairs><vt:vector size=""2"" baseType=""variant""><vt:variant><vt:lpstr>Worksheets</vt:lpstr></vt:variant><vt:variant><vt:i4>1</vt:i4></vt:variant></vt:vector></HeadingPairs><TitlesOfParts><vt:vector size=""1"" baseType=""lpstr""><vt:lpstr>Sheet1</vt:lpstr></vt:vector></TitlesOfParts><Company></Company><LinksUpToDate>false</LinksUpToDate><SharedDoc>false</SharedDoc><HyperlinksChanged>false</HyperlinksChanged><AppVersion>16.0300</AppVersion></Properties>";
            StartExstream(xContents, xFilename);

            xFilename = @"C:\Users\david\Desktop\Book3\docProps\core.xml";
            xContents = @"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?><cp:coreProperties xmlns:cp=""http://schemas.openxmlformats.org/package/2006/metadata/core-properties"" xmlns:dc=""http://purl.org/dc/elements/1.1/"" xmlns:dcterms=""http://purl.org/dc/terms/"" xmlns:dcmitype=""http://purl.org/dc/dcmitype/"" xmlns:xsi=""http://www.w3.org/2001/XMLSchema-instance""><dc:creator>David Tallett</dc:creator><cp:lastModifiedBy>David Tallett</cp:lastModifiedBy><dcterms:created xsi:type=""dcterms:W3CDTF"">2021-10-26T15:47:15Z</dcterms:created><dcterms:modified xsi:type=""dcterms:W3CDTF"">2021-10-26T15:47:35Z</dcterms:modified></cp:coreProperties>";
            StartExstream(xContents, xFilename);

            xFilename = @"C:\Users\david\Desktop\Book3\xl\styles.xml";
            xContents = @"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?><styleSheet xmlns=""http://schemas.openxmlformats.org/spreadsheetml/2006/main"" xmlns:mc=""http://schemas.openxmlformats.org/markup-compatibility/2006"" mc:Ignorable=""x14ac x16r2 xr"" xmlns:x14ac=""http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac"" xmlns:x16r2=""http://schemas.microsoft.com/office/spreadsheetml/2015/02/main"" xmlns:xr=""http://schemas.microsoft.com/office/spreadsheetml/2014/revision""><fonts count=""1"" x14ac:knownFonts=""1""><font><sz val=""11""/><color theme=""1""/><name val=""Calibri""/><family val=""2""/><scheme val=""minor""/></font></fonts><fills count=""2""><fill><patternFill patternType=""none""/></fill><fill><patternFill patternType=""gray125""/></fill></fills><borders count=""1""><border><left/><right/><top/><bottom/><diagonal/></border></borders><cellStyleXfs count=""1""><xf numFmtId=""0"" fontId=""0"" fillId=""0"" borderId=""0""/></cellStyleXfs><cellXfs count=""1""><xf numFmtId=""0"" fontId=""0"" fillId=""0"" borderId=""0"" xfId=""0""/></cellXfs><cellStyles count=""1""><cellStyle name=""Normal"" xfId=""0"" builtinId=""0""/></cellStyles><dxfs count=""0""/><tableStyles count=""0"" defaultTableStyle=""TableStyleMedium2"" defaultPivotStyle=""PivotStyleLight16""/><extLst><ext uri=""{EB79DEF2-80B8-43e5-95BD-54CBDDF9020C}"" xmlns:x14=""http://schemas.microsoft.com/office/spreadsheetml/2009/9/main""><x14:slicerStyles defaultSlicerStyle=""SlicerStyleLight1""/></ext><ext uri=""{9260A510-F301-46a8-8635-F512D64BE5F5}"" xmlns:x15=""http://schemas.microsoft.com/office/spreadsheetml/2010/11/main""><x15:timelineStyles defaultTimelineStyle=""TimeSlicerStyleLight1""/></ext></extLst></styleSheet>";
            StartExstream(xContents, xFilename);

            xFilename = @"C:\Users\david\Desktop\Book3\xl\workbook.xml";
            xContents = @"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?><workbook xmlns=""http://schemas.openxmlformats.org/spreadsheetml/2006/main"" xmlns:r=""http://schemas.openxmlformats.org/officeDocument/2006/relationships"" xmlns:mc=""http://schemas.openxmlformats.org/markup-compatibility/2006"" mc:Ignorable=""x15 xr xr6 xr10 xr2"" xmlns:x15=""http://schemas.microsoft.com/office/spreadsheetml/2010/11/main"" xmlns:xr=""http://schemas.microsoft.com/office/spreadsheetml/2014/revision"" xmlns:xr6=""http://schemas.microsoft.com/office/spreadsheetml/2016/revision6"" xmlns:xr10=""http://schemas.microsoft.com/office/spreadsheetml/2016/revision10"" xmlns:xr2=""http://schemas.microsoft.com/office/spreadsheetml/2015/revision2""><fileVersion appName=""xl"" lastEdited=""7"" lowestEdited=""7"" rupBuild=""24430""/><workbookPr defaultThemeVersion=""166925""/><mc:AlternateContent xmlns:mc=""http://schemas.openxmlformats.org/markup-compatibility/2006""><mc:Choice Requires=""x15""><x15ac:absPath url=""C:\Users\david\Desktop\"" xmlns:x15ac=""http://schemas.microsoft.com/office/spreadsheetml/2010/11/ac""/></mc:Choice></mc:AlternateContent><xr:revisionPtr revIDLastSave=""0"" documentId=""8_{C633700D-2D40-49EE-8C5E-2561E28A6758}"" xr6:coauthVersionLast=""47"" xr6:coauthVersionMax=""47"" xr10:uidLastSave=""{00000000-0000-0000-0000-000000000000}""/><bookViews><workbookView xWindow=""-120"" yWindow=""-120"" windowWidth=""29040"" windowHeight=""15840"" xr2:uid=""{934C5B62-1DC1-4322-BAE8-00D615BD2FB3}""/></bookViews><sheets><sheet name=""Sheet1"" sheetId=""1"" r:id=""rId1""/></sheets><calcPr calcId=""191029""/><extLst><ext uri=""{140A7094-0E35-4892-8432-C4D2E57EDEB5}"" xmlns:x15=""http://schemas.microsoft.com/office/spreadsheetml/2010/11/main""><x15:workbookPr chartTrackingRefBase=""1""/></ext><ext uri=""{B58B0392-4F1F-4190-BB64-5DF3571DCE5F}"" xmlns:xcalcf=""http://schemas.microsoft.com/office/spreadsheetml/2018/calcfeatures""><xcalcf:calcFeatures><xcalcf:feature name=""microsoft.com:RD""/><xcalcf:feature name=""microsoft.com:Single""/><xcalcf:feature name=""microsoft.com:FV""/><xcalcf:feature name=""microsoft.com:CNMTM""/><xcalcf:feature name=""microsoft.com:LET_WF""/></xcalcf:calcFeatures></ext></extLst></workbook>";
            StartExstream(xContents, xFilename);

            xFilename = @"C:\Users\david\Desktop\Book3\xl\_rels\workbook.xml.rels";
            xContents = @"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?><Relationships xmlns=""http://schemas.openxmlformats.org/package/2006/relationships""><Relationship Id=""rId3"" Type=""http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles"" Target=""styles.xml""/><Relationship Id=""rId2"" Type=""http://schemas.openxmlformats.org/officeDocument/2006/relationships/theme"" Target=""theme/theme1.xml""/><Relationship Id=""rId1"" Type=""http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet"" Target=""worksheets/sheet1.xml""/></Relationships>";
            StartExstream(xContents, xFilename);

            xFilename = @"C:\Users\david\Desktop\Book3\xl\theme\theme1.xml";
            xContents = @"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?><a:theme xmlns:a=""http://schemas.openxmlformats.org/drawingml/2006/main"" name=""Office Theme""><a:themeElements><a:clrScheme name=""Office""><a:dk1><a:sysClr val=""windowText"" lastClr=""000000""/></a:dk1><a:lt1><a:sysClr val=""window"" lastClr=""FFFFFF""/></a:lt1><a:dk2><a:srgbClr val=""44546A""/></a:dk2><a:lt2><a:srgbClr val=""E7E6E6""/></a:lt2><a:accent1><a:srgbClr val=""4472C4""/></a:accent1><a:accent2><a:srgbClr val=""ED7D31""/></a:accent2><a:accent3><a:srgbClr val=""A5A5A5""/></a:accent3><a:accent4><a:srgbClr val=""FFC000""/></a:accent4><a:accent5><a:srgbClr val=""5B9BD5""/></a:accent5><a:accent6><a:srgbClr val=""70AD47""/></a:accent6><a:hlink><a:srgbClr val=""0563C1""/></a:hlink><a:folHlink><a:srgbClr val=""954F72""/></a:folHlink></a:clrScheme><a:fontScheme name=""Office""><a:majorFont><a:latin typeface=""Calibri Light"" panose=""020F0302020204030204""/><a:ea typeface=""""/><a:cs typeface=""""/><a:font script=""Jpan"" typeface=""游ゴシック Light""/><a:font script=""Hang"" typeface=""맑은 고딕""/><a:font script=""Hans"" typeface=""等线 Light""/><a:font script=""Hant"" typeface=""新細明體""/><a:font script=""Arab"" typeface=""Times New Roman""/><a:font script=""Hebr"" typeface=""Times New Roman""/><a:font script=""Thai"" typeface=""Tahoma""/><a:font script=""Ethi"" typeface=""Nyala""/><a:font script=""Beng"" typeface=""Vrinda""/><a:font script=""Gujr"" typeface=""Shruti""/><a:font script=""Khmr"" typeface=""MoolBoran""/><a:font script=""Knda"" typeface=""Tunga""/><a:font script=""Guru"" typeface=""Raavi""/><a:font script=""Cans"" typeface=""Euphemia""/><a:font script=""Cher"" typeface=""Plantagenet Cherokee""/><a:font script=""Yiii"" typeface=""Microsoft Yi Baiti""/><a:font script=""Tibt"" typeface=""Microsoft Himalaya""/><a:font script=""Thaa"" typeface=""MV Boli""/><a:font script=""Deva"" typeface=""Mangal""/><a:font script=""Telu"" typeface=""Gautami""/><a:font script=""Taml"" typeface=""Latha""/><a:font script=""Syrc"" typeface=""Estrangelo Edessa""/><a:font script=""Orya"" typeface=""Kalinga""/><a:font script=""Mlym"" typeface=""Kartika""/><a:font script=""Laoo"" typeface=""DokChampa""/><a:font script=""Sinh"" typeface=""Iskoola Pota""/><a:font script=""Mong"" typeface=""Mongolian Baiti""/><a:font script=""Viet"" typeface=""Times New Roman""/><a:font script=""Uigh"" typeface=""Microsoft Uighur""/><a:font script=""Geor"" typeface=""Sylfaen""/><a:font script=""Armn"" typeface=""Arial""/><a:font script=""Bugi"" typeface=""Leelawadee UI""/><a:font script=""Bopo"" typeface=""Microsoft JhengHei""/><a:font script=""Java"" typeface=""Javanese Text""/><a:font script=""Lisu"" typeface=""Segoe UI""/><a:font script=""Mymr"" typeface=""Myanmar Text""/><a:font script=""Nkoo"" typeface=""Ebrima""/><a:font script=""Olck"" typeface=""Nirmala UI""/><a:font script=""Osma"" typeface=""Ebrima""/><a:font script=""Phag"" typeface=""Phagspa""/><a:font script=""Syrn"" typeface=""Estrangelo Edessa""/><a:font script=""Syrj"" typeface=""Estrangelo Edessa""/><a:font script=""Syre"" typeface=""Estrangelo Edessa""/><a:font script=""Sora"" typeface=""Nirmala UI""/><a:font script=""Tale"" typeface=""Microsoft Tai Le""/><a:font script=""Talu"" typeface=""Microsoft New Tai Lue""/><a:font script=""Tfng"" typeface=""Ebrima""/></a:majorFont><a:minorFont><a:latin typeface=""Calibri"" panose=""020F0502020204030204""/><a:ea typeface=""""/><a:cs typeface=""""/><a:font script=""Jpan"" typeface=""游ゴシック""/><a:font script=""Hang"" typeface=""맑은 고딕""/><a:font script=""Hans"" typeface=""等线""/><a:font script=""Hant"" typeface=""新細明體""/><a:font script=""Arab"" typeface=""Arial""/><a:font script=""Hebr"" typeface=""Arial""/><a:font script=""Thai"" typeface=""Tahoma""/><a:font script=""Ethi"" typeface=""Nyala""/><a:font script=""Beng"" typeface=""Vrinda""/><a:font script=""Gujr"" typeface=""Shruti""/><a:font script=""Khmr"" typeface=""DaunPenh""/><a:font script=""Knda"" typeface=""Tunga""/><a:font script=""Guru"" typeface=""Raavi""/><a:font script=""Cans"" typeface=""Euphemia""/><a:font script=""Cher"" typeface=""Plantagenet Cherokee""/><a:font script=""Yiii"" typeface=""Microsoft Yi Baiti""/><a:font script=""Tibt"" typeface=""Microsoft Himalaya""/><a:font script=""Thaa"" typeface=""MV Boli""/><a:font script=""Deva"" typeface=""Mangal""/><a:font script=""Telu"" typeface=""Gautami""/><a:font script=""Taml"" typeface=""Latha""/><a:font script=""Syrc"" typeface=""Estrangelo Edessa""/><a:font script=""Orya"" typeface=""Kalinga""/><a:font script=""Mlym"" typeface=""Kartika""/><a:font script=""Laoo"" typeface=""DokChampa""/><a:font script=""Sinh"" typeface=""Iskoola Pota""/><a:font script=""Mong"" typeface=""Mongolian Baiti""/><a:font script=""Viet"" typeface=""Arial""/><a:font script=""Uigh"" typeface=""Microsoft Uighur""/><a:font script=""Geor"" typeface=""Sylfaen""/><a:font script=""Armn"" typeface=""Arial""/><a:font script=""Bugi"" typeface=""Leelawadee UI""/><a:font script=""Bopo"" typeface=""Microsoft JhengHei""/><a:font script=""Java"" typeface=""Javanese Text""/><a:font script=""Lisu"" typeface=""Segoe UI""/><a:font script=""Mymr"" typeface=""Myanmar Text""/><a:font script=""Nkoo"" typeface=""Ebrima""/><a:font script=""Olck"" typeface=""Nirmala UI""/><a:font script=""Osma"" typeface=""Ebrima""/><a:font script=""Phag"" typeface=""Phagspa""/><a:font script=""Syrn"" typeface=""Estrangelo Edessa""/><a:font script=""Syrj"" typeface=""Estrangelo Edessa""/><a:font script=""Syre"" typeface=""Estrangelo Edessa""/><a:font script=""Sora"" typeface=""Nirmala UI""/><a:font script=""Tale"" typeface=""Microsoft Tai Le""/><a:font script=""Talu"" typeface=""Microsoft New Tai Lue""/><a:font script=""Tfng"" typeface=""Ebrima""/></a:minorFont></a:fontScheme><a:fmtScheme name=""Office""><a:fillStyleLst><a:solidFill><a:schemeClr val=""phClr""/></a:solidFill><a:gradFill rotWithShape=""1""><a:gsLst><a:gs pos=""0""><a:schemeClr val=""phClr""><a:lumMod val=""110000""/><a:satMod val=""105000""/><a:tint val=""67000""/></a:schemeClr></a:gs><a:gs pos=""50000""><a:schemeClr val=""phClr""><a:lumMod val=""105000""/><a:satMod val=""103000""/><a:tint val=""73000""/></a:schemeClr></a:gs><a:gs pos=""100000""><a:schemeClr val=""phClr""><a:lumMod val=""105000""/><a:satMod val=""109000""/><a:tint val=""81000""/></a:schemeClr></a:gs></a:gsLst><a:lin ang=""5400000"" scaled=""0""/></a:gradFill><a:gradFill rotWithShape=""1""><a:gsLst><a:gs pos=""0""><a:schemeClr val=""phClr""><a:satMod val=""103000""/><a:lumMod val=""102000""/><a:tint val=""94000""/></a:schemeClr></a:gs><a:gs pos=""50000""><a:schemeClr val=""phClr""><a:satMod val=""110000""/><a:lumMod val=""100000""/><a:shade val=""100000""/></a:schemeClr></a:gs><a:gs pos=""100000""><a:schemeClr val=""phClr""><a:lumMod val=""99000""/><a:satMod val=""120000""/><a:shade val=""78000""/></a:schemeClr></a:gs></a:gsLst><a:lin ang=""5400000"" scaled=""0""/></a:gradFill></a:fillStyleLst><a:lnStyleLst><a:ln w=""6350"" cap=""flat"" cmpd=""sng"" algn=""ctr""><a:solidFill><a:schemeClr val=""phClr""/></a:solidFill><a:prstDash val=""solid""/><a:miter lim=""800000""/></a:ln><a:ln w=""12700"" cap=""flat"" cmpd=""sng"" algn=""ctr""><a:solidFill><a:schemeClr val=""phClr""/></a:solidFill><a:prstDash val=""solid""/><a:miter lim=""800000""/></a:ln><a:ln w=""19050"" cap=""flat"" cmpd=""sng"" algn=""ctr""><a:solidFill><a:schemeClr val=""phClr""/></a:solidFill><a:prstDash val=""solid""/><a:miter lim=""800000""/></a:ln></a:lnStyleLst><a:effectStyleLst><a:effectStyle><a:effectLst/></a:effectStyle><a:effectStyle><a:effectLst/></a:effectStyle><a:effectStyle><a:effectLst><a:outerShdw blurRad=""57150"" dist=""19050"" dir=""5400000"" algn=""ctr"" rotWithShape=""0""><a:srgbClr val=""000000""><a:alpha val=""63000""/></a:srgbClr></a:outerShdw></a:effectLst></a:effectStyle></a:effectStyleLst><a:bgFillStyleLst><a:solidFill><a:schemeClr val=""phClr""/></a:solidFill><a:solidFill><a:schemeClr val=""phClr""><a:tint val=""95000""/><a:satMod val=""170000""/></a:schemeClr></a:solidFill><a:gradFill rotWithShape=""1""><a:gsLst><a:gs pos=""0""><a:schemeClr val=""phClr""><a:tint val=""93000""/><a:satMod val=""150000""/><a:shade val=""98000""/><a:lumMod val=""102000""/></a:schemeClr></a:gs><a:gs pos=""50000""><a:schemeClr val=""phClr""><a:tint val=""98000""/><a:satMod val=""130000""/><a:shade val=""90000""/><a:lumMod val=""103000""/></a:schemeClr></a:gs><a:gs pos=""100000""><a:schemeClr val=""phClr""><a:shade val=""63000""/><a:satMod val=""120000""/></a:schemeClr></a:gs></a:gsLst><a:lin ang=""5400000"" scaled=""0""/></a:gradFill></a:bgFillStyleLst></a:fmtScheme></a:themeElements><a:objectDefaults/><a:extraClrSchemeLst/><a:extLst><a:ext uri=""{05A4C25C-085E-4340-85A3-A5531E510DB2}""><thm15:themeFamily xmlns:thm15=""http://schemas.microsoft.com/office/thememl/2012/main"" name=""Office Theme"" id=""{62F939B6-93AF-4DB8-9C6B-D6C7DFDC589F}"" vid=""{4A3C46E8-61CC-4603-A589-7422A47A8E4A}""/></a:ext></a:extLst></a:theme>";
            StartExstream(xContents, xFilename);

            xFilename = @"C:\Users\david\Desktop\Book3\xl\worksheets\sheet1.xml";
            xContents = @"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?><worksheet xmlns=""http://schemas.openxmlformats.org/spreadsheetml/2006/main"" xmlns:r=""http://schemas.openxmlformats.org/officeDocument/2006/relationships"" xmlns:mc=""http://schemas.openxmlformats.org/markup-compatibility/2006"" mc:Ignorable=""x14ac xr xr2 xr3"" xmlns:x14ac=""http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac"" xmlns:xr=""http://schemas.microsoft.com/office/spreadsheetml/2014/revision"" xmlns:xr2=""http://schemas.microsoft.com/office/spreadsheetml/2015/revision2"" xmlns:xr3=""http://schemas.microsoft.com/office/spreadsheetml/2016/revision3"" xr:uid=""{54E3D330-4E78-4755-89E0-1AADACAC4953}""><dimension ref=""A1:A3""/><sheetViews><sheetView tabSelected=""1"" workbookViewId=""0""><selection activeCell=""A4"" sqref=""A4""/></sheetView></sheetViews><sheetFormatPr defaultRowHeight=""15"" x14ac:dyDescent=""0.25""/><sheetData><row r=""1"" spans=""1:1"" x14ac:dyDescent=""0.25""><c r=""A1""><v>1</v></c></row><row r=""2"" spans=""1:1"" x14ac:dyDescent=""0.25""><c r=""A2""><v>2</v></c></row><row r=""3"" spans=""1:1"" x14ac:dyDescent=""0.25""><c r=""A3""><v>3</v></c></row></sheetData><pageMargins left=""0.7"" right=""0.7"" top=""0.75"" bottom=""0.75"" header=""0.3"" footer=""0.3""/></worksheet>";
            StartExstream(xContents, xFilename);

            // Keep the console window open in debug mode.
            System.Console.WriteLine("Press any key to exit.");
            System.Console.ReadKey();

            bool StartExstream(string strLine, string strFileName)
            {
                // Write the string to a file.
                using (StreamWriter outputFile = new StreamWriter(strFileName))
                {
                    outputFile.WriteLine(strLine);
                    return true;
                }
            }
        }
    }
}

Finally ZIP the folder structure containing the XML -

namespace ZipFolder
// .NET Framework 4.7.2
// https://stackoverflow.com/questions/15241889/i-didnt-find-zipfile-class-in-the-system-io-compression-namespace?answertab=votes#tab-top
{
    class Program
    {
        static void Main(string[] args)
        {
            string xlPath = @"C:\Users\david\Desktop\Book3.xlsx";
            string folderPath = @"C:\Users\david\Desktop\Book3";

            System.IO.Compression.ZipFile.CreateFromDirectory(folderPath, xlPath);

            // Keep the console window open in debug mode.
            System.Console.WriteLine("Press any key to exit.");
            System.Console.ReadKey();
        }
    }
}

This produces an Excel file named Book3.xlsx which is valid and opens cleanly in Excel 365 on Windows 11.

The result is a very simple Excel spreadsheet but you may need to reverse engineer a more complex version. Here is the code to unzip a .xlsx file.

namespace UnZipXL
// .NET Framework 4.7.2
// https://stackoverflow.com/questions/15241889/i-didnt-find-zipfile-class-in-the-system-io-compression-namespace?answertab=votes#tab-top
{
    class Program
    {
        static void Main(string[] args)
        {
            string XLPath = @"C:\Users\david\Desktop\Book2.xlsx";
            string extractPath = @"C:\Users\david\Desktop\extract";

            System.IO.Compression.ZipFile.ExtractToDirectory(XLPath, extractPath);

            // Keep the console window open in debug mode.
            System.Console.WriteLine("Press any key to exit.");
            System.Console.ReadKey();
        }
    }
}

Update:

Here is a code fragment to update the Excel file. This is very simple again.

//
// https://docs.microsoft.com/en-us/dotnet/standard/io/how-to-write-text-to-a-file
// .NET Framework 4.7.2
//
using System.IO;

namespace UpdateWorksheet5
{
    class Program
    {
        static void Main(string[] args)
        {
            string xContents = @"a";
            string xFilename = @"a";

            xFilename = @"C:\Users\david\Desktop\Book3\xl\worksheets\sheet1.xml";
            xContents = @"<?xml version=""1.0"" encoding=""UTF-8"" standalone=""yes""?><worksheet xmlns=""http://schemas.openxmlformats.org/spreadsheetml/2006/main"" xmlns:r=""http://schemas.openxmlformats.org/officeDocument/2006/relationships"" xmlns:mc=""http://schemas.openxmlformats.org/markup-compatibility/2006"" mc:Ignorable=""x14ac xr xr2 xr3"" xmlns:x14ac=""http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac"" xmlns:xr=""http://schemas.microsoft.com/office/spreadsheetml/2014/revision"" xmlns:xr2=""http://schemas.microsoft.com/office/spreadsheetml/2015/revision2"" xmlns:xr3=""http://schemas.microsoft.com/office/spreadsheetml/2016/revision3"" xr:uid=""{54E3D330-4E78-4755-89E0-1AADACAC4953}""><dimension ref=""A1:A3""/><sheetViews><sheetView tabSelected=""1"" workbookViewId=""0""><selection activeCell=""A4"" sqref=""A4""/></sheetView></sheetViews><sheetFormatPr defaultRowHeight=""15"" x14ac:dyDescent=""0.25""/><sheetData><row r=""1"" spans=""1:1"" x14ac:dyDescent=""0.25""><c r=""A1""><v>1</v></c></row><row r=""2"" spans=""1:1"" x14ac:dyDescent=""0.25""><c r=""A2""><v>2</v></c></row><row r=""3"" spans=""1:1"" x14ac:dyDescent=""0.25""><c r=""A3""><v>3</v></c></row></sheetData><pageMargins left=""0.7"" right=""0.7"" top=""0.75"" bottom=""0.75"" header=""0.3"" footer=""0.3""/></worksheet>";
            xContents = xContents.Remove(941, 1).Insert(941, "0"); //  character to replace is at 942 => index 941
            StartExstream(xContents, xFilename);

            // Keep the console window open in debug mode.
            System.Console.WriteLine("Press any key to exit.");
            System.Console.ReadKey();

            bool StartExstream(string strLine, string strFileName)
            {
                // Write the string to a file.
                using (StreamWriter outputFile = new StreamWriter(strFileName))
                {
                    outputFile.WriteLine(strLine);
                    return true;
                }
            }
        }
    }
}

Update 2 - This code works almost unchanged except for the folder paths on a Mac. Using Microsoft Excel Online, .NET Framework 3.1, Visual Studio 2019 for Mac, MacOS Monterey 12.1.

Solution 45 - C#

check this out no need for third party libraries you can simply export datatable data to excel file using this

var dt = "your code for getting data into datatable";
            Response.ClearContent();
            Response.AddHeader("content-disposition", string.Format("attachment;filename={0}.xls", DateTime.Now.ToString("yyyy-MM-dd")));
            Response.ContentType = "application/vnd.ms-excel";
            string tab = "";
            foreach (DataColumn dataColumn in dt.Columns)
            {
                Response.Write(tab + dataColumn.ColumnName);
                tab = "\t";
            }
            Response.Write("\n");
            int i;
            foreach (DataRow dataRow in dt.Rows)
            {
                tab = "";
                for (i = 0; i < dt.Columns.Count; i++)
                {
                    Response.Write(tab + dataRow[i].ToString());
                    tab = "\t";
                }
                Response.Write("\n");
            }
            Response.End();

Solution 46 - C#

I am using following code for create excel 2007 file which create the file and write in that file but when i open the file but it give me error that exel cannot open the file bcz file might be coruupted or extension of the file is not compatible. but if i used .xls for file it work fines

for (int i = 0; i < TotalFile; i++)
{
    Contact.Clear();
    if (innerloop == SplitSize)
    {
        for (int j = 0; j < SplitSize; j++)
        {
            string strContact = DSt.Tables[0].Rows[i * SplitSize + j][0].ToString();
            Contact.Add(strContact);
        }
        string strExcel = strFileName + "_" + i.ToString() + ".xlsx";
                         File.WriteAllLines(strExcel, Contact.ToArray());
    }
}

also refer link

http://dotnet-magic.blogspot.in/2011/10/createformat-excel-file-from-cnet.html

Attributions

All content for this solution is sourced from the original question on Stackoverflow.

The content on this page is licensed under the Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license.

Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestionmistrmarkView Question on Stackoverflow
Solution 1 - C#Mike WebbView Answer on Stackoverflow
Solution 2 - C#Jan KällmanView Answer on Stackoverflow
Solution 3 - C#PellaredView Answer on Stackoverflow
Solution 4 - C#Leniel MaccaferriView Answer on Stackoverflow
Solution 5 - C#PanosView Answer on Stackoverflow
Solution 6 - C#Joe EricksonView Answer on Stackoverflow
Solution 7 - C#Forgotten SemicolonView Answer on Stackoverflow
Solution 8 - C#NateView Answer on Stackoverflow
Solution 9 - C#ManuelView Answer on Stackoverflow
Solution 10 - C#GEOCHETView Answer on Stackoverflow
Solution 11 - C#Petr SnobeltView Answer on Stackoverflow
Solution 12 - C#Mike GledhillView Answer on Stackoverflow
Solution 13 - C#Sam WarwickView Answer on Stackoverflow
Solution 14 - C#ManiacZXView Answer on Stackoverflow
Solution 15 - C#Davis JebarajView Answer on Stackoverflow
Solution 16 - C#biozincView Answer on Stackoverflow
Solution 17 - C#Dimi TakisView Answer on Stackoverflow
Solution 18 - C#Vihana KewalramaniView Answer on Stackoverflow
Solution 19 - C#EMPView Answer on Stackoverflow
Solution 20 - C#Sachin DhirView Answer on Stackoverflow
Solution 21 - C#Aaron PowellView Answer on Stackoverflow
Solution 22 - C#EisbaerView Answer on Stackoverflow
Solution 23 - C#GauravView Answer on Stackoverflow
Solution 24 - C#MagicKatView Answer on Stackoverflow
Solution 25 - C#Ryan LundyView Answer on Stackoverflow
Solution 26 - C#user529824View Answer on Stackoverflow
Solution 27 - C#Simen SView Answer on Stackoverflow
Solution 28 - C#TaterheadView Answer on Stackoverflow
Solution 29 - C#NickView Answer on Stackoverflow
Solution 30 - C#Stefan KoelleView Answer on Stackoverflow
Solution 31 - C#ScaleOvenStoveView Answer on Stackoverflow
Solution 32 - C#View Answer on Stackoverflow
Solution 33 - C#AlexDevView Answer on Stackoverflow
Solution 34 - C#Roman.PavelkoView Answer on Stackoverflow
Solution 35 - C#Craig McView Answer on Stackoverflow
Solution 36 - C#Michael MainerView Answer on Stackoverflow
Solution 37 - C#Mauricio KennyView Answer on Stackoverflow
Solution 38 - C#Miguel TomásView Answer on Stackoverflow
Solution 39 - C#Gayan Chinthaka DharmarathnaView Answer on Stackoverflow
Solution 40 - C#Vladimir VenegasView Answer on Stackoverflow
Solution 41 - C#Vijay DodamaniView Answer on Stackoverflow
Solution 42 - C#Klaus OberdalhoffView Answer on Stackoverflow
Solution 43 - C#tohaView Answer on Stackoverflow
Solution 44 - C#user10186832View Answer on Stackoverflow
Solution 45 - C#ShubhamView Answer on Stackoverflow
Solution 46 - C#saurabh27View Answer on Stackoverflow