title: Join DataTable with List<SomeObject>
body: <p>I have a DataTable and a List of objects. I need to return all rows in the DataTable where a property in the List is a certain value. The List is only used for filtering the datatable (but the filter column isn't containined in the datatable).</p>
  
  <p>I'm sure this must be possible with LINQ.</p>
  
  <p>The DataTable contains:</p>
  
  <pre><code>MembershipID  Username   Password   
  1              blah        blah      
  2              blah        blah      
  3              blah        blah      
  </code></pre>
  
  <p>My List contains:</p>
  
  <pre><code>MembershipID  Profile1   Profile2   Profile3 DifferentID   
  1              blah        blah      blah    A             
  2              blah        blah      blah    B             
  3              blah        blah      blah    C            
  </code></pre>
  
  <p>I need to return (as a DataTable) - eg: for GetUsersByDifferentID("B"):</p>
  
  <pre><code>MembershipID  Username   Password   
  2              blah        blah      
  ...
  </code></pre>
  
  <p>I could get the second table as a DataTable if that would make it easier, but I think what I need is possible with LINQ. I just can't get my head around the magic syntax.</p>