How about:

    var x = from c in dt.Columns.Cast&lt;DataColumn&gt;()
            select c.ColumnName;

You could also use:

    var x = from DataColumn c in myDataTable.Columns
            select c.ColumnName

It will effectively do the same as Dave&#39;s code: &quot;in a query expression, an explicitly typed iteration variable translates to an invocation of Cast&lt;TResult&gt;(IEnumerable)&quot;, according to the [`Enumerable.Cast&lt;TResult&gt; Method`](http://msdn.microsoft.com/en-us/library/bb341406.aspx) MSDN article.

With Linq Method Syntax:

    var x = myDataTable.Columns.Cast&lt;DataColumn&gt;().Select(c =&gt; c.ColumnName);

I would like to know what the pros and cons are for using an Anemic Domain Model (see link below).

[Fowler Article][1]


  [1]: http://www.martinfowler.com/bliki/AnemicDomainModel.html &quot;Fowler Article&quot;

Anemic Domain Model: Pros/Cons

I&#39;m going through MSIL and noticing there are a lot of [nop][1] instructions in the MSIL.

The MSDN article says they take no action and are used to fill space if the opcode is patched. They&#39;re used a lot more in debug builds than release builds.

I know that these kinds of statements are used in assembly languages to align later instructions, but why are MSIL nops needed in MSIL?

(Editor&#39;s note: the accepted answer is about machine-code NOPs, not MSIL/CIL NOPs which the question originally asked about.)


  [1]: http://msdn.microsoft.com/en-us/library/system.reflection.emit.opcodes.nop.aspx

What&#39;s the purpose of the CIL nop opcode?

I&#39;m trying to perform a simple LINQ query on the Columns property of a DataTable:

    from c in myDataTable.Columns.AsQueryable()
        select c.ColumnName

However, what I get is this:

&gt;Could not find an implementation of the query pattern for source type &#39;System.Linq.IQueryable&#39;. &#39;Select&#39; not found.  Consider explicitly specifying the type of the range variable &#39;c&#39;.

How can I get the DataColumnCollection to play nice with LINQ?

Querying DataColumnCollection with LINQ

I'm trying to perform a simple LINQ query on the Columns property of a DataTable:
<pre><code class="hljs language-csharp">from c in myDataTable.Columns.AsQueryable()
 select c.ColumnName
</code></pre>
However, what I get is this:
>Could not find an implementation of the query pattern for source type 'System.Linq.IQueryable'. 'Select' not found. Consider explicitly specifying the type of the range variable 'c'.
How can I get the DataColumnCollection to play nice with LINQ?

How can I replace Line Breaks within a string in C#?

Replace Line Breaks in a String C#

I have a char in c#:

    char foo = &#39;2&#39;;

Now I want to get the 2 into an int.  I find that Convert.ToInt32 returns the actual decimal value of the char and not the number 2.  The following will work:

    int bar = Convert.ToInt32(new string(foo, 1));

int.parse only works on strings as well.  

Is there no native function in C# to go from a char to int without making it a string?  I know this is trivial but it just seems odd that there&#39;s nothing native to directly make the conversion.

Convert char to int in C#

When I try to add a HTTP header key/value pair on a `WebRequest` object, I get the following exception:

&gt; This header must be modified using the appropriate property

I&#39;ve tried adding new values to the `Headers` collection by using the Add() method but I still get the same exception.

    webRequest.Headers.Add(HttpRequestHeader.Referer, &quot;http://stackoverflow.com&quot;);

I can get around this by casting the WebRequest object to a HttpWebRequest and setting the properties such as `httpWebReq.Referer =&quot;http://stackoverflow.com&quot;`, but this only works for a handful of headers that are exposed via properties.

I&#39;d like to know if there&#39;s a way to get a finer grained control over modifying headers with a request for a remote resource.

Cannot set some HTTP headers when using System.Net.WebRequest

I need to setup an application that watches for files being created in a directory, both locally or on a network drive.

Would the `FileSystemWatcher` or polling on a timer would be the best option. I have used both methods in the past, but not extensively. 

What issues (performance, reliability etc.) are there with either method? 

FileSystemWatcher vs polling to watch for file changes

How can I launch an application using C#?

Requirements:
Must work on [Windows&amp;nbsp;XP][1] and [Windows&amp;nbsp;Vista][2].

I have seen a sample from DinnerNow.net sampler that only works in Windows&amp;nbsp;Vista.

  [1]: http://en.wikipedia.org/wiki/Windows_XP
  [2]: http://en.wikipedia.org/wiki/Windows_Vista


Launching an application (.EXE) from C#?

How do I properly convert two columns from SQL (2008) using Linq into a Dictionary (for caching)?

I currently loop through the IQueryable b/c I can&#39;t get the ToDictionary method to work. Any ideas?
This works:

    var query = from p in db.Table
                select p;
    
    Dictionary&lt;string, string&gt; dic = new Dictionary&lt;string, string&gt;();
    
    foreach (var p in query)
    {
        dic.Add(sub.Key, sub.Value);
    }


What I&#39;d really like to do is something like this, which doesn&#39;t seem to work:

    var dic = (from p in db.Table
                 select new {p.Key, p.Value })
                .ToDictionary&lt;string, string&gt;(p =&gt; p.Key);

But I get this error: 
Cannot convert from &#39;System.Linq.IQueryable&lt;AnonymousType#1&gt;&#39; to &#39;System.Collections.Generic.IEnumerable&lt;string&gt;&#39;

Linq-to-SQL ToDictionary()

I am using T4 to generate some screens and middle-tier code for a project, and would like to use Linq to simplify some of my template code.  However, when I try to use Linq, the template reports a syntax error.


How can I use Linq in a T4 template?

I have a small project that require a storage (I choose SQLite) and I got good result with the [ADO DLL for .Net for Sqlite][1].

After the Install, I noticed that it contain a SQLLinq.dll. Before investigating too much effort, and because I haven&#39;t see any good example on the web, I would like to know if anyone got any good result with SQLite and LINQ?

*If linqtosql work the same way what ever the SQL database, let me know it. I was interesting with the Dll when I saw it because I never use Linqtosql before and I thought it would be a great opportunity to try,

  [1]: http://sqlite.phxsoftware.com/

LINQ with SQLite (linqtosql)

After I read a bunch of LINQ related stuff, I suddenly realized that no articles introduce how to write asynchronous LINQ query. 

Suppose we use LINQ to SQL, below statement is clear. However, if the SQL database responds slowly, then the thread using this block of code would be hindered.

    var result = from item in Products where item.Price &gt; 3 select item.Name;
    foreach (var name in result)
    {
        Console.WriteLine(name);
    }

Seems that current LINQ query spec doesn&#39;t provide support to this.

Is there any way to do asynchronous programming LINQ? It works like there is a callback 
notification when results are ready to use without any blocking delay on I/O.



How to write Asynchronous LINQ query?

What is the difference between `IQueryable&lt;T&gt;` and `IEnumerable&lt;T&gt;`?

-----------------

See also [What&#39;s the difference between IQueryable and IEnumerable][1] that overlaps with this question.


  [1]: https://stackoverflow.com/questions/2433306/whats-the-difference-between-iqueryable-and-ienumerable?rq=1

What is the difference between IQueryable&lt;T&gt; and IEnumerable&lt;T&gt;?

If I have 2 DataTables (dtOne and dtTwo) and I want to merge them and put them in another DataTable (dtAll).  How can I do this in C#?  I tried the Merge statement on the datatable, but this returns void.  Does Merge preserve the data?  For example, if I do:

     dtOne.Merge(dtTwo);

Does dtOne change or does dtTwo change and if either one changes, do the changes preserve?

I know I can&#39;t do this because Merge returns void, but I want to be able to store the Merger of both dtOne and dtTwo in dtAll:

    //Will Not work, How do I do this
    dtAll = dtOne.Merge(dtTwo);


 

Merge 2 DataTables and store in a new one

In a sorted table, it&#39;s common to have an up or a down arrow indicating the sort style. However, I&#39;m having some trouble determining which direction the arrow should point. In an ASC sort, characters are sorted 1-9A-Za-z. Should the arrow point up or down?

I&#39;ve found implementations of both on the web, so that didn&#39;t help me much: [Up][1] and [Down][2] (you have to create the table first).

Is there a hard and fast rule for this? I find myself able to justify both implementations. Which method do you use? Which is more intuitive to you and why?

**Edit:** Some of you have suggested alternate implementations like rising bars or having letters with an arrow indicating sort direction. Great suggestions. I&#39;m definitely open to other options. The less ambiguous, the better. It might be picky, but I&#39;d really like there to be minimal or no confusion on the part of the user.

**Edit:** I ended up going with the rising and falling bars for now. It&#39;s not standard, but seems less ambiguous than the triangles. The current sort column shows three bars, small to large (left to right) for ASC, the opposite for DESC. Other sortable columns have no bars by default, but hovering over any sortable column heading (including the current) shows bars depicting how the table will be sorted if that column heading is clicked.

  [1]: http://yoast.com/articles/sortable-table/
  [2]: http://www.frequency-decoder.com/demo/table-sort-revisited/dynamic/

Which direction should the arrows point in a sorted table?

I have few methods that returns different Generic Lists. 

Exists in .net any class static method or whatever to convert any list into a datatable? The only thing that i can imagine is use Reflection to do this.

IF i have this:

    List&lt;Whatever&gt; whatever = new List&lt;Whatever&gt;();
    

(This next code doesn&#39;t work of course, but i would like to have the possibility of:
    
    DataTable dt = (DataTable) whatever;



Convert generic List/Enumerable to DataTable?

I am trying to convert a generic collection (List&lt;MySimpleClass&gt;) to a DataTable. I found the following code to help me do this:

    // Sorry about indentation
    public class CollectionHelper
    {
    private CollectionHelper()
    {
    }

    // this is the method I have been using
    public static DataTable ConvertTo&lt;T&gt;(IList&lt;T&gt; list)
    {
        DataTable table = CreateTable&lt;T&gt;();
        Type entityType = typeof(T);
        PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(entityType);

        foreach (T item in list)
        {
            DataRow row = table.NewRow();

            foreach (PropertyDescriptor prop in properties)
            {
                row[prop.Name] = prop.GetValue(item);
            }

            table.Rows.Add(row);
        }

        return table;
    }    

    public static DataTable CreateTable&lt;T&gt;()
    {
        Type entityType = typeof(T);
        DataTable table = new DataTable(entityType.Name);
        PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(entityType);

        foreach (PropertyDescriptor prop in properties)
        {
            // HERE IS WHERE THE ERROR IS THROWN FOR NULLABLE TYPES
            table.Columns.Add(prop.Name, prop.PropertyType);
        }

        return table;
    }
    }


My problem is that when I change one of the properties of MySimpleClass to a nullable type, I get the following error:

`DataSet does not support System.Nullable&lt;&gt;.`

How can I do this with Nullable properties/fields in my class?

.NET - Convert Generic Collection to DataTable

I would like to append one DataTable to another DataTable. I see the DataTable class has two methods; &quot;Load(IDataReader)&quot; and &quot;Merge(DataTable)&quot;.  From the documentation, both appear to &#39;merge&#39; the incoming data with the existing DataTable if rows exist. I will be doing the merge in a data access layer.

I could use an `IDataReader` and use the Load method to merge the DataTables. Or I could load a DataSet using the `IDataReader`, get the DataTable from the DataSet, and then use the Merge method to merge the DataTables.

I was wondering if someone could tell me which is the proper method to use?

Alternatively, let me know if you have a different suggestion on how to accomplish this task.

Content Type	Original Author	Original Content on Stackoverflow
Question	David Brown	View Question on Stackoverflow
Solution 1 - C#	Dave Markle	View Answer on Stackoverflow
Solution 2 - C#	Cobra	View Answer on Stackoverflow
Solution 3 - C#	MarkusE	View Answer on Stackoverflow

Querying DataColumnCollection with LINQ

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

Solution 3 - C#

What's the purpose of the CIL nop opcode?

Anemic Domain Model: Pros/Cons

Attributions