How I can filter a Datatable?

I use a DataTable with Information about Users and I want search a user or a list of users in this DataTable. I try it butit don't work :(

Here is my c# code:

 public DataTable GetEntriesBySearch(string username,string location,DataTable table)
        {
            list = null;
            list = table;

            string expression;
            string sortOrder;

            expression = "Nachname = 'test'";
            sortOrder = "nachname DESC";

            DataRow[] rows =  list.Select(expression, sortOrder);

            list = null; // for testing
            list = new DataTable(); // for testing
 
            foreach (DataRow row in rows)
            {
                list.ImportRow(row);
            }

            return list; 
        }

You can use DataView.

DataView dv = new DataView(yourDatatable);
dv.RowFilter = "query"; // query example = "id = 10"

http://www.csharp-examples.net/dataview-rowfilter/

If you're using at least .NET 3.5, i would suggest to use Linq-To-DataTable instead since it's much more readable and powerful:

DataTable tblFiltered = table.AsEnumerable()
          .Where(row => row.Field<String>("Nachname") == username
                   &&   row.Field<String>("Ort") == location)
          .OrderByDescending(row => row.Field<String>("Nachname"))
          .CopyToDataTable();

Above code is just an example, actually you have many more methods available.

Remember to add using System.Linq; and for the AsEnumerable extension method a reference to the System.Data.DataSetExtensions dll (How).

use it:

.CopyToDataTable()

example:

string _sqlWhere = "Nachname = 'test'";
string _sqlOrder = "Nachname DESC";

DataTable _newDataTable = yurDateTable.Select(_sqlWhere, _sqlOrder).CopyToDataTable();

Sometimes you actually want to return a DataTable than a DataView. So a DataView was not good in my case and I guess few others would want that too. Here is what I used to do

myDataTable.select("myquery").CopyToDataTable()

This will filter myDataTable which is a DataTable and return a new DataTable

Hope someone will find that is useful

For anybody who work in VB.NET (just in case)

Dim dv As DataView = yourDatatable.DefaultView

dv.RowFilter ="query" ' ex: "parentid = 0"

It is better to use DataView for this task.

Example of the using it you can find in this post: https://stackoverflow.com/questions/10009675/how-to-filter-data-in-dataview

Hi we can use ToLower Method sometimes it is not filter.

EmployeeId = Session["EmployeeID"].ToString();
var rows = dtCrewList.AsEnumerable().Where
   (row => row.Field<string>("EmployeeId").ToLower()== EmployeeId.ToLower());

   if (rows.Any())
   {
        tblFiltered = rows.CopyToDataTable<DataRow>();
   }