title: Make field email validate and required
body: <p>I need to have a textbox be validated as an email address, and make it a required field. I also need to restrict the email addresses to a specific domain name only (e.g. @example.com).</p>
  
  <pre><code>&lt;asp:TextBox ID="EmailTextBox" runat="server" Text='&lt;%# Bind("Email") %&gt;' 
                                      MaxLength="50" /&gt;
  </code></pre>
  
  <p>What is the best approach to this?</p>