Validated validating c
To avoid this, you need to code the event handling to reset the Cancel value only when the mouse is inside the form's client area.This allows the mouse to close the form using the Close button in the title bar.However, if one inputs 01/09/14 into the field when the date should be entered as 09/01/14, the computer sees this as still valid.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.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.Table 3.4 details some important properties of the Key Press Event Args class.
When a user presses a key, three events are fired in order: The Key Press event can be used to intercept input keyboard characters and perform validation tasks through the use of the Key Press Event Args class before the Key Up event is handled.
NOTE By default, only the control, which currently has the focus, responds to the Key Down, Key Press, and Key Up events.
However, if you set the Key Preview property of a form to true, the form can also handle the same three events before the control with the current focus handles them, allowing two tiers of keystroke-level validationat the form level and at the control level.
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.
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).