title: Define a column as nullable in System.Data.DataTable
body: <p>I need to define a <code>System.Data.DataTable</code> in C# VS2013; in one column, it may be int or null.</p>
  <p>But I got:</p>
  <blockquote>
  <p>DataSet does not support System.Nullable&lt;&gt;.</p>
  </blockquote>
  <p>For the definition:</p>
  <pre><code>public DataTable myDataTable
  myDataTable = new DataTable(&quot;myName&quot;);
  myDataTable.Columns.Add(&quot;ID&quot;, typeof(Int32)); 
  myDataTable.Columns.Add(&quot;value1&quot;, typeof(Int32?)); // run time error 
  myDataTable.Columns.Add(&quot;value2&quot;, typeof(Int32?)); 
  </code></pre>
  <p>Any ideas? Work around?</p>
  <p>After making the column nullable,</p>
  <pre><code>DataColumn dc = myDataTable.Columns.Add(&quot;value1&quot;, typeof(Int32));
  dc.AllowDBNull = true;
  </code></pre>
  <p>When I queried it, I got</p>
  <blockquote>
  <p>Sequence contains no elements.</p>
  </blockquote>
  <p>Please see the UPDATE.</p>
  <p><strong>UPDATE</strong></p>
  <pre><code>int? result = (from r in myDataTable.AsEnumerable()
                 where r.Field&lt;Int32&gt;(&quot;ID&quot;) == givenID
                     &amp;&amp; r.Field&lt;Int32?&gt;(&quot;value1&quot;) == givenValue1
                 select r.Field&lt;Int32&gt;(&quot;value2&quot;)).First();
  </code></pre>