Obtaining textbox value in change event handler

Question

I\'ve written a form that performs queries asynchronously as text is typed into a textbox, however I somewhat arbitrarily seem to get the following error th

Answer 1

The form had a lingering data source. I'm not sure why this would cause to the behavior described above, especially considering the text box controls are unbound, however since removing the data source the text boxes are behaving as expected.