title: How do you group by multiple columns in LINQ TO SQL?
body: <p>How do you group by multiple columns in LINQ TO SQL?</p>
  
  <pre><code>db.Table.GroupBy(a =&gt; a.column1.ToString() + a.column2.ToString())
  </code></pre>
  
  <p>It seems ugly and with poor performance, and I don't even know if it works. Which is the right way to do it?</p>