![]() When you press a key on a control, three events take place in the followingorder: You saw how to use the various controls to limit input in Chapter 2,"Controls." I'll cover the rest of the techniques in thissection. ![]() Restrict entry in some data fields by enabling or disabling themdepending on the state of other fields.Īnalyze the contents of the data field as a whole and warn the user ofany incorrect values when the user attempts to leave the field or close thewindow. Somefields might require the user to enter only alphabetic values but no numericvalues or special characters in that case, you can accept the keystrokes foralphabetic characters while rejecting others. These allow usersto select from a set of given values rather than permitting free keyboardentry.Ĭapture the user's keystrokes and analyze them for validity. Restrict the values that a field can accept by using standard controlslike combo boxes, list boxes, radio buttons and check boxes. You canuse various techniques for validating data, including these: The most obvioustime to ensure the validity of data is at the time of data entry itself. Whendesigning an application that interacts with the user to accept data, you mustensure that the entered data is acceptable to the application. It's a truism of the computer world that garbage-in is garbage-out. MCAD/MCSD Training Guide (70-306): Developing and Implementing Windows-Based Applications with Visual Basic.NET and Visual Studio.NET
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