Hello Marcus,

Yes it has been a while and yet, I am glad that you managed to resolve this issue. 
Thank you for your feedback. 

Hi Ivaylo

I'm sure your suggestion would work fine but this issue was from more than 6 months ago so we have solved our problem by going about things in a completely different way.

Regards,

Marcus

Hello,

I was just wondering did you have a chance to try my suggestion.
If you have any concerns or questions, please feel free to contact me, I will be glad to help you.

Hello Marcus,
Thank you for posting in the community!

Instead of checking for the KeyDown event, it is possible to check the cell values of the row to be added. In case of null value, the RowAdding event could be canceled using something similar as these code lines:

<EditingClientEvents RowAdding="CheckCellsValidation" />

        function CheckCellsValidation(sender, eventArgs) {

             var cellsArray = [];
             var value1 = eventArgs.get_row().get_cellByColumnKey("DepartmentID").get_value();
             var value2 = eventArgs.get_row().get_cellByColumnKey("DepartmentName").get_value(); 

            cellsArray.push(value1);
            cellsArray.push(value2);

            for (var i in cellsArray) {
                if (cellsArray[i] === null) {
                    eventArgs.set_cancel(true);
                }
            }
        }