I have a control that inherits from a RegularExpressionValidator and I need an instance of it on a page, but from what I can tell you can't add this without creating it in a separate library and adding the library to your toolbox and dropping an instance on your page.

I could add it through the code-behind but there are problems with the ControlToValidate property of Validators.

I know it's fairly straightforward to create a separate library to house the control but I can't justify that just for one control.