title: Error while taking SUM() of column in datatable
body: <pre><code>DataTable dtStock = new DataTable();
  DataColumn dcTotalCases = new DataColumn("TotalCases");
  dcTotalCases.DataType = System.Type.GetType("System.Int32");
  dcTotalCases.ReadOnly = false;
  dtStock.Columns.Add(dcTotalCases);
  </code></pre>
  
  <p>Method 1</p>
  
  <pre><code>int sum = Convert.ToInt32(dtStock.Compute("Sum([TotalCases]) ", "[TotalCases] &lt;&gt; ''"));
  </code></pre>
  
  <p>When I use this method, I get an error </p>
  
  <blockquote>
    <p>Invalid usage of aggregate function Sum() and Type: String.</p>
  </blockquote>
  
  <p>Method 2</p>
  
  <pre><code>int sum = Convert.ToInt32(dtStock.Compute("SUM(Convert([TotalCases], 'System.Int32'))", "");
  </code></pre>
  
  <p>When I use this method, I get an error </p>
  
  <blockquote>
    <p>Syntax error in aggregate argument: Expecting a single column argument
    with possible 'Child' qualifier.</p>
  </blockquote>
  
  <p>Please help me...</p>