KeyEventHandler Delegado

Definición

Espacio de nombres:

System.Windows.Forms

Ensamblado:

System.Windows.Forms.dll

Source:

KeyEventHandler.cs

Representa el método que controlará los eventos KeyUp o KeyDown de un Control.

C#

public delegate void KeyEventHandler(object? sender, KeyEventArgs e);

Parámetros

sender

Object

Origen del evento.

e

KeyEventArgs

Objeto KeyEventArgs que contiene los datos del evento.

Ejemplos

C#

private void treeView1_KeyDown(object sender, KeyEventArgs e)
{
   /* If the 'Alt' and 'E' keys are pressed,
      * allow the user to edit the TreeNode label. */
   if(e.Alt && e.KeyCode == Keys.E)
         
   {
      treeView1.LabelEdit = true;
      // If there is a TreeNode under the mouse cursor, begin editing. 
      TreeNode editNode = treeView1.GetNodeAt(
         treeView1.PointToClient(System.Windows.Forms.Control.MousePosition));
      if(editNode != null)
      { 
         editNode.BeginEdit();
      }
   }
}

private void treeView1_AfterLabelEdit(object sender, NodeLabelEditEventArgs e)
{
   // Disable the ability to edit the TreeNode labels.
   treeView1.LabelEdit = false;
}

C#

// 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)
    {
        // Stop the character from being entered into the control since it is non-numerical.
        e.Handled = true;
    }
}

Comentarios

Cuando se crea un delegado KeyEventHandler, se identifica el método que controlará el evento. Para asociar el evento al controlador, se debe agregar una instancia del delegado al evento. Siempre que se produce el evento, se llama a su controlador, a menos que se quite el delegado. Para obtener más información sobre cómo controlar eventos con delegados, vea Control y generación de eventos.

Métodos de extensión

Se aplica a

Consulte también

• OnKeyUp(KeyEventArgs)
• KeyUp
• OnKeyDown(KeyEventArgs)
• KeyDown
• KeyEventArgs
• OnKeyPress(KeyPressEventArgs)
• KeyPress
• KeyPressEventArgs