Programming .NET Windows Applications

Some Examples

In this section, you will see examples of events in use. In the first example, you will use keyboard events to capture keystrokes, showing what information is available about each keystroke. The next example will use keystroke information and the Validating event to control and validate the contents entered into a text box.

Keyboard Events

It is often useful or necessary to capture keystrokes and then take action based on the details related to that keystroke. For example, you may want to disallow certain characters or convert all lowercase characters to uppercase. Keyboard events provide access to this type of functionality.

The three events listed in Table 4-5 are raised when the user presses a key on the keyboard.

Table 4-5. Key Events for all controls

Event	Event data	Description
KeyDown	KeyEventArgs	Raised when a key is pressed. The KeyDown event occurs prior to the KeyPress event.
KeyPress	KeyPressEventArgs	Raised when a character generating key is pressed. The KeyPress event occurs after the KeyDown event and before the KeyUp event.
KeyUp	KeyEventArgs	Raised when a key is released.

The KeyDown and KeyPress events may seem somewhat redundant, but they fire at different points in the keyboard event stream and contain different information in the EventArgs object.

The KeyEventArgs event data associated with the KeyDown and KeyUp events provides low-level information about the keystroke, listed in Table 4-6. This information allows you to determine, for example, ...