Hi Amine
As per your previous update, we have checked the reported problem by creating the sample with database, but we could not reproduce the reported issue in our Current product version. It is working fine from our side. We suspect that, this exception occurs if the property name provided in the RowValidating event is not to be available in the ItemSource bound to SfDataGrid. Could you please ensure this in your application? If the issue persists, then share your application or modified the sample to reproduce the reported issue to proceed further on this.
Please refer the sample from the below link
Regards,
Balamurugan R