asp:RequiredFieldValidator
<h2>This is my first question in stackoverflow.com. I am working on a school project which I have to validate the input from the user. Everytime the page load, it give the server error message. Please see the codes, and the error message after.</h2>

<pre><code>&lt;div&gt;
&lt;table&gt;
&lt;td&gt;
&lt;asp:RadioButton ID="RadioButton1" runat="server"&gt;&lt;/asp:RadioButton&gt;
&lt;asp:RequiredFieldValidator ID="validateCheck" runat="server"  ControlToValidate="RadioButton1"   ErrorMessage="Please Enter" Display="Dynamic"&gt;&lt;/asp:RequiredFieldValidator&gt;             
&lt;/td&gt;
&lt;/table&gt;
&lt;/div&gt;
</code></pre>

<hr>

<pre><code>Server Error in '/' Application.
Control 'RadioButton1' referenced by the ControlToValidate property of 'validateCheck' cannot be validated.
</code></pre>
