<com:TContent ID="Content"> <com:TDatePicker id="test" /> <com:TActiveCustomValidator ID="validator1" ControlToValidate="test" OnServerValidate="ChkDate" ErrorMessage="*"> <prop:ClientSide OnValidationError="$('error').innerHTML='Error'" OnValidationSuccess="$('error').innerHTML='Success'" ObserveChanges="false" /> </com:TActiveCustomValidator> <span id="error"></span> <com:TButton ID="button1" Text="ok"/> </com:TContent>