title: How to place a required field validator inside a GridView TextBox
body: <p>I have a <code>GridView</code> with some <code>TemplateField</code> items containing <code>TextBox</code> controls. I would like to add a required field validator on it. This is my code:</p>
  
  <pre><code>&lt;asp:TemplateField HeaderText="vid"&gt;
      &lt;EditItemTemplate&gt;
           &lt;asp:TextBox ID="txtvid" runat="server" Width="150px"
                              Text='&lt;%# Bind("vid") %&gt;'&gt;
           &lt;/asp:TextBox&gt;
      &lt;/EditItemTemplate&gt;
      &lt;ItemTemplate&gt;
           &lt;asp:Label 
                     ID="lblvid" runat="server" 
                     Text='&lt;%# Bind("vid") %&gt;'&gt;
           &lt;/asp:Label&gt;
      &lt;/ItemTemplate&gt;
   &lt;/asp:TemplateField&gt;
  </code></pre>
  
  <p>How do I place a required field validator on <code>txtvid</code>?</p>