This page demonstrates how to implement editor-level validation using the Ajax technique.

Assume the values of the Email field must be unique in the table. The uniqueness of this field defined at the server side. To check this condition at the client side, you can issue an Ajax request from the OnInsertFormEditorValueChanged event handler.

For simplicity in the example below the default value for the Email field is preset to an email address that already exists in the table, so all you need to test the editor validation is to open the Insert form and go from Email editor to another one. Click the button to get familiar with the event handler code.