title: LinQ - Left Join Two DataTables
body: <p>I am wondering if anyone can help me.
  I am new to LINQ and still trying to understand how it fits together.</p>
  
  <p>I have a simple left join query in SQL, returning all transactions that are on table 1 that do not exist in table 2.  Both tables are identical in structure.</p>
  
  <pre><code>SELECT Table1.*
  FROM Table1 LEFT JOIN Table2 ON Table1.DealReference = Table2.DealReference
  WHERE (((Table2.DealReference) Is Null));
  </code></pre>
  
  <p>Can someone please guide me, how to achieve the same in LinQ.</p>
  
  <p>I am using the following DataTables:</p>
  
  <pre><code>    Dim currentDataTable = _DataTable1.AsEnumerable
      Dim previousDataTable = _DataTable2.AsEnumerable
  </code></pre>
  
  <p>I am looking to have the results output back into a datatable.</p>
  
  <p>Thanks</p>
  
  <p>BM</p>