When we click on Autoocomplete box we are ascertaining the below issue,
i have also glued the code where i am able to find the issue,
Can anyone help me to resolve this issue ?
Looking at the attached image I believe that the e.OriginalSource, that you are trying to cast is of type ScrollViewer and not a RadWatermarkTextBox. I am not sure which event you try to handle, but it seems that the e.OriginalSource will not work for you to find the textbox portion of the control. I would suggest you to use the RadAutoCompleteBox' SearchText property instead.