title: How to compute datatable with multiple filters?
body: <p>I want to sum the value of a certain column on my <code>datatable</code>, where column x is equal to a value AND column y is equal to another value.  I can implement this when I just filter on column X as follows:</p>
  
  <pre><code>dt.Compute("Sum([Cost])", "[COLUMNX] = 'blah'");  
  </code></pre>
  
  <p>This works fine, however I now want to add another column to the filter, so something like <code>dt.Compute("Sum([Cost])", "[COLUMNX] = 'blah'", "[COLUMNY] = 'blah'");</code></p>
  
  <p>How can I filter on two different columns please.</p>