Registration is fast, simple and absolutely free book is just starting to get into the code here.
the author claims there is not previous knowledge needed, but at this page he is throwing code at us and not telling us where it put it. jtwl_jtwl_, Now I don't have the book you're working with but I down loaded the code to have a look at it and it appears that the event should go in its own method like this. Jason "Is the glass half full, half empty, or twice as large as it needs to be?
You do know, however, that the effect of calling the method should be the same no matter who is calling, so you can simply cast the text box.
The procedure is exactly the same as for the two previous handlers, but the validation code is different because occupation must be Programmer or an empty string to be valid. The ASCII values for the characters between 0 and 9 lie between 48 and 57, so you make sure that the character is within this range. The ASCII value 8 is the Backspace key, and for editing reasons, you allow this to slip through.
In this example, there are a number of criteria to enforce to ensure that the values are correct: .
The reason that this event needs a special handler is that should the validation fail, there must be a way to prevent any further processing.
If you were to cancel further processing, that would effectively mean that it would be impossible to leave a text box until the data entered is valid.
The Because more than one text box is using this method to handle the event, you cannot be sure which is calling the function.
This is a simple thing as you've already written the method to perform this check, and you simply subscribe to the button while in a text box with invalid data without the background color changing to red.
Setting the tells the control that it shouldn't do anything else with the character, and so if the key pressed isn't a digit or a backspace, it is not shown.
As it is now, the control is not marked as invalid or valid.
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