title: Variable selection of columns in a sql query
body: <p>In ASP.NET, can a 'select-query' be dynamic as follows ?
  This throws an error, how can this be achieved?</p>
  
  <pre><code>SelectCommand="SELECT TOP 30 [date],**[@tc]** FROM [tbl_TC] WHERE ([ID] = ?) ORDER BY [date]"&gt;
  &lt;SelectParameters&gt;
  **&lt;asp:QueryStringParameter Name="@tc" QueryStringField="tc" /&gt;**
  &lt;asp:QueryStringParameter Name="ID" QueryStringField="pid" Type="String" /&gt;
  &lt;/SelectParameters&gt;
  </code></pre>