This server-side setting will bind your javascript method to the OnKeyUp event, which fires on the client any time a key is pressed while the textbox has focus.
My problem is I can't reduce the size of first text box because line underneath text also will be reduced which I don't want to happen. I want the original textbox with line to be as is and overlay another textbox to show message and show/hide it based on length of routing number. When I overlay textbox, design time it looks fine. But in preview, message gets display below routing number ...
I have a number of TextBox's in my window and would like to provide the UpdateSource trigger in a style under Windows.Resources: