<com:TContent ID="Content"> <com:TImageButton ImageUrl="http://pradosoft.github.io/docs/powered.gif" Text="Foo" ValidationGroup="Foo" OnClick="buttonClicked" /> <com:TTextBox ID="FooTextBox" Text="sometext" /> <com:TRequiredFieldValidator ValidationGroup="Foo" ControlToValidate="FooTextBox" Text="Field required." /> <com:TLabel ID="Result" /> </com:TContent>