title: Multiple group by and Sum LINQ
body: <p>I have a products sales table that looks like this:</p>
  
  <pre><code>saleDate     prod        qty
  10/22/09     soap        10
  09/22/09     pills       05
  09/25/09     soap        06
  09/25/09     pills       15
  </code></pre>
  
  <p>I need to make the SUM of each MONTH so the final table would look like this:</p>
  
  <pre><code>saleDate     prod        qty
  10/09        soap        10
  09/09        soap        06
  09/09        pills       20
  </code></pre>
  
  <p>Can I do this with LINQ?</p>