Hello,
The problem comes from the fact that TextBox does not handle KeyDown event (when MaxLength is reached), therefore KeyDown event is handled by RadGridView and RadGridView takes the appropriate action (put the current cell in edit mode, navigates to other cell, ...). You can easily handle this case with a few lines of code:
And the code behind:
Let me know if this does not help.
Regards,
Nedyalko Nikolov
the Telerik team