title: Add up values from two datatables into a new datatable
body: <p>I have two strongly typed Datatable (<code>dt1</code>): </p>
  
  <pre><code>|FirstName|LastName|Val1|Val2|
  |Tony     |Stark   |34  |35  |
  |Steve    |Rogers  |12  |23  |
  |Natasha  |Romanoff|2   |100 |
  </code></pre>
  
  <p>and the second (<code>dt2</code>)</p>
  
  <pre><code>|FirstName|LastName|Val1|Val2|
  |Tony     |Stark   |16  |5   |
  |Bruce    |Banner  |2   |1   |
  |Steve    |Rogers  |54  |40  |
  </code></pre>
  
  <p>I try to create a new Datatable where I add up the values for the persons. I need a outer join since I need all persons and the value in the second table is halved. </p>
  
  <p>So the result should looks like:</p>
  
  <pre><code>|FirstName|LastName|Val1|Val2|
  |Tony     |Stark   |42  |37.5|
  |Steve    |Rogers  |39  |43  |
  |Natasha  |Romanoff|2   |100 |
  |Bruce    |Banner  |1   |0.5 |
  </code></pre>
  
  <p>My approach was with LINQ:</p>
  
  <pre><code>Dim query = 
  from a in ds1.Table1
  Join b in ds2.Table2
  On a.FirstName + a.LastName Equals b.FirstName + b.Lastname
  Select New With {
  .FirstName = a.FirstName,
  .LastName = a.LastName,
  .Val1 = a.Val1 + b.Val1 *0.5,
  .Val2 = a.Val2 + b.Val2 *0.5
  }
  </code></pre>
  
  <p>But I dont get all persons with the approach. I also tried </p>
  
  <pre><code>Dim query = 
  From a in ds1.Table1
  From b in ds2.Table2
  Select New With{
  Key .KeyName = a.FirstName + a.LastName = b.FirstName + b.FirstName,
  .Val1 = a.Val1 + b.Val1 *0.5,
  .Val2 = a.Val2 + b.Val2 * 0.5
  }
  </code></pre>
  
  <p>Now I get many entries for each person. Could anyone help me get this done. I dont know if there is maybe another approach without Linq to solve this.</p>