What are the valid server controls that can be used in the CustomValidator.ControlToValidate property?
<p>I'm wondering if anyone knows what are the valid Asp.Net server controls that can be used with the CustomValidator.ControlToValidate property.  </p>

<p>For example I know that you can validate a TextBox.</p>

<p>However, when using some other types of controls I receive the following error:</p>

<blockquote>
  <p>System.Web.HttpException: Control 'xxx' referenced by the ControlToValidate property of 'yyy' cannot be validated.</p>
</blockquote>

<p>This happens when using RadioButton controls for example.</p>

<p>Is there an established list of valid Server controls that can be used in the ControlToValidate property?</p>
