Hello,
Why did the validation controls stop working after the data source of GridView was changed to Entity Framework from SqlDataSource on a Web form which has double master pages? The combination isn't allowed?
The validation controls "RequiredFieldValidator", "RangeValidator", and "ValidationSummary" had worked just before I changed the data source to Entity Framework.
I'm coding it by C# in Visual Studio Professional 2017.
Please let me know if you need more information because I'm not familiar with questioning about like this.
Best regards,
Herokey