ASP.NET :HyperLinkColumn - 'HyperLinkColumn' is not a known element. This can occur if there is a compilation error in the Web site
<p>I am getting the following error:
Element 'HyperLinkColumn' is not a known element. This can occur if there is a compilation error in the Web site.</p>

<p>Within my GridView before I had:</p>

<pre><code>    &lt;asp:BoundField DataField="ProID" HeaderStyle-BackColor="#0066cc" 
     HeaderStyle-Font-Size="7pt" HeaderStyle-HorizontalAlign="center" 
     HeaderText="ProID" ItemStyle-HorizontalAlign="center" /&gt;
</code></pre>

<p>I replaced that with:</p>

<pre><code>     &lt;asp:HyperLinkColumn DataNavigateUrlField="ProID" 
      DataNavigateUrlFormatString="pro.aspx?pro={0}" 
      DataTextField="ProID" HeaderText="ProID" SortExpression="ProID"&gt;
      &lt;HeaderStyle HorizontalAlign="Left" /&gt;
      &lt;ItemStyle HorizontalAlign="Left" /&gt;
      &lt;/asp:HyperLinkColumn&gt;
</code></pre>

<p>Not sure why it is giving me this message. My goal is simply to make that column into a hyplink so that I can have the user to to the designated page.</p>
