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KeyEventHandler (Delegado)

.NET Framework 3.5

Otras versiones

Actualización: noviembre 2007

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

Espacio de nombres: System.Windows.Forms
Ensamblado: System.Windows.Forms (en System.Windows.Forms.dll)

Sintaxis

C++

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public delegate void KeyEventHandler(
	Object sender,
	KeyEventArgs e
)

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/** @delegate */
public delegate void KeyEventHandler(
	Object sender,
	KeyEventArgs e
)

JScript

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JScript no admite delegados.

Parámetros

sender: Tipo: System.Object
Origen del evento.

e: Tipo: System.Windows.Forms.KeyEventArgs
KeyEventArgs que contiene los datos del evento.

Comentarios

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

Ejemplos

C++

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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 mose cursor, begin editing. 
      TreeNode editNode = treeView1.GetNodeAt(
         treeView1.PointToClient(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;
}

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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.get_Alt() && e.get_KeyCode() == Keys.E) {
        treeView1.set_LabelEdit(true);
        // If there is a TreeNode under the mose cursor, begin editing. 
        TreeNode editNode = treeView1.GetNodeAt(treeView1.PointToClient(
            Control.get_MousePosition()));
        if (editNode != null) {
            editNode.BeginEdit();
        }
    }
} //treeView1_KeyDown

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

C++

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// 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;
            }
        }
    }
}

// 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;
    }
}

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// Boolean flag used to determine when a character other than a number 
// is entered.
private boolean 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.get_KeyCode().CompareTo(Keys.D0)) < 0 
        || (e.get_KeyCode().CompareTo(Keys.D9) > 0)) {

        // Determine whether the keystroke is a number from the keypad.
        if ((e.get_KeyCode().CompareTo(Keys.NumPad0) < 0 
            || (e.get_KeyCode().CompareTo(Keys.NumPad9)) > 0)) {

            // Determine whether the keystroke is a backspace.
            if (!(e.get_KeyCode().Equals(Keys.Back))) {
                    // A non-numerical keystroke was pressed.
                    // Set the flag to true and evaluate in KeyPress event.
                    nonNumberEntered = true;
            }
        }
    }
} //textBox1_KeyDown

// 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.set_Handled(true);
    }
} //textBox1_KeyPress

Plataformas

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile para Smartphone, Windows Mobile para Pocket PC

.NET Framework y .NET Compact Framework no admiten todas las versiones de cada plataforma. Para obtener una lista de las versiones compatibles, vea Requisitos de sistema de .NET Framework.

Información de versión