custom validation or custom rule to check unique username for kendo UI grid
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I am using MVC architecture with webAPI. I have used kendo grid with Popup edit feature, and when I click on "Add new record" link then a popup appears with the various fields. I want to validate my username field. The validation on username is to check whether the entered username is unique or not. If the username is not unique, then it should raise a validation saying that "Username is not unique". For this purpose, I want to write a custom validation for kendo grid which will call the server side function and return the value as true if the username is not unique to my client side function and raise a validation message. Is there a way by which I can validate my kendo grid by writing custom validation or custom rule.

Kindly help me with this issue.

Regards,
Karthik