Validated validating c

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When using the Validating event to retain the focus in a control until you receive a valid input value, you can prevent the user from being able to obtain help on what constituted a valid input value by clicking another control such as the Help button in the toolbar.This is a result of the default setting (true) of the Causes Validation property of the Button control.Validating user input before hand provides a better solution than very complex error-handling code that might add a great deal of resource overhead to your program.Four basic techniques are used to validate user input: Restriction of allowable values within a control was discussed at greater length in Chapter 2, "Controls on Forms." In addition to simply restricting input to a selection from a list of values, control properties can be configured to further limit possible input values.The options for the Character Casing property are Normal (the default, which does not change the case of input characters), Upper (changes all the characters to uppercase), and Lower (changes all the characters to lowercase).

To make your application as robust as possible, the best solution to invalid or incorrect user input is to prevent the entry of "bad" data as often as possible.

The Validating event is ideal for input value validation.

You can write code to check the values presented and display an error message to the user or prevent the loss of focus from the current control until the value has been corrected.

Table 3.4 details some important properties of the Key Press Event Args class.

The Key Press event fires only for keys that generate character values, excluding function, control, and cursor-movement keys.

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