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Método Control.OnKeyPress (KeyPressEventArgs)

 

Aciona o evento KeyPress.

Namespace:   System.Windows.Forms
Assembly:  System.Windows.Forms (em System.Windows.Forms.dll)

protected virtual void OnKeyPress(
	KeyPressEventArgs e
)

Parâmetros

e
Type: System.Windows.Forms.KeyPressEventArgs

Um KeyPressEventArgs que contém os dados do evento.

Raising an event invokes the event handler through a delegate. For more information, see Handling and Raising Events.

The M:System.Windows.Forms.Control.OnKeyPress(System.Windows.Forms.KeyPressEventArgs) method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

Observações para os Herdeiros:

When overriding M:System.Windows.Forms.Control.OnKeyPress(System.Windows.Forms.KeyPressEventArgs) in a derived class, be sure to call the base class's M:System.Windows.Forms.Control.OnKeyPress(System.Windows.Forms.KeyPressEventArgs) method so that registered delegates receive the event.

The following code example uses the E:System.Windows.Forms.Control.KeyPress event to prevent characters from entering the control.

// Boolean flag used to determine when a character other than a number is entered.
private bool nonNumberEntered = false;

// Handle the KeyDown event to determine the type of character entered into the control.
private void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
    // Initialize the flag to false.
    nonNumberEntered = false;

    // Determine whether the keystroke is a number from the top of the keyboard.
    if (e.KeyCode < Keys.D0 || e.KeyCode > Keys.D9)
    {
        // Determine whether the keystroke is a number from the keypad.
        if (e.KeyCode < Keys.NumPad0 || e.KeyCode > Keys.NumPad9)
        {
            // Determine whether the keystroke is a backspace.
            if(e.KeyCode != Keys.Back)
            {
                // A non-numerical keystroke was pressed.
                // Set the flag to true and evaluate in KeyPress event.
                nonNumberEntered = true;
            }
        }
    }
    //If shift key was pressed, it's not a number.
    if (Control.ModifierKeys == Keys.Shift) {
        nonNumberEntered = true;
    }
}

// This event occurs after the KeyDown event and can be used to prevent
// characters from entering the control.
private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
    // Check for the flag being set in the KeyDown event.
    if (nonNumberEntered == true)
    {
        // Stop the character from being entered into the control since it is non-numerical.
        e.Handled = true;
    }
}

.NET Framework
Disponível desde 1.1
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