title: How to merge two DataTables by primary key and foreign key (right join)?
body: <p>Is there a way, to merge two dataTables table1 and table2 by different keys?</p>
  
  <p>Want to do <code>dataTable.Merge</code> by <code>t1 PK_id</code> and <code>t2 ParentId</code>. Is this possible if <code>ParentId</code> is not a <code>PK</code>? </p>
  
  <p><em><strong>table1</em></strong>   </p>
  
  <pre><code>PK_id   Name
  --------------
    1     test1
    2     test2
    3     test3
  </code></pre>
  
  <p><em><strong>table2</em></strong>    </p>
  
  <pre><code>PK_id2  ShortName  ParentId
  ---------------------------
     1       a           1
     2       b           1
     3       c           2
  </code></pre>
  
  <p><em><strong>Result is a right join</em></strong>   </p>
  
  <pre><code>PK_id   Name   PK_id2  ShortName  ParentId
  ------------------------------------------------
     1    test1     1        a          1
     1    test1     2        b          1
     2    test2     3        c          2
     3    test3    null     null      null
  </code></pre>
  
  <p>Thanks in advance.</p>