Control.OnKeyDown(KeyEventArgs) Control.OnKeyDown(KeyEventArgs) Control.OnKeyDown(KeyEventArgs) Control.OnKeyDown(KeyEventArgs) Method

Définition

Déclenche l'événement KeyDown.Raises the KeyDown event.

protected:
 virtual void OnKeyDown(System::Windows::Forms::KeyEventArgs ^ e);
protected virtual void OnKeyDown (System.Windows.Forms.KeyEventArgs e);
abstract member OnKeyDown : System.Windows.Forms.KeyEventArgs -> unit
override this.OnKeyDown : System.Windows.Forms.KeyEventArgs -> unit
Protected Overridable Sub OnKeyDown (e As KeyEventArgs)

Paramètres

e
KeyEventArgs KeyEventArgs KeyEventArgs KeyEventArgs

KeyEventArgs qui contient les données d'événement.A KeyEventArgs that contains the event data.

Exemples

L’exemple de code suivant utilise KeyDown l’événement pour déterminer le type de caractère entré dans le contrôle.The following code example uses the KeyDown event to determine the type of character entered into the control.

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

   // Handle the KeyDown event to determine the type of character entered into the control.
   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.
   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;
      }
   }
// 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;
    }
}

' Boolean flag used to determine when a character other than a number is entered.
Private nonNumberEntered As Boolean = False


' Handle the KeyDown event to determine the type of character entered into the control.
Private Sub textBox1_KeyDown(sender As Object, e As System.Windows.Forms.KeyEventArgs) _
     Handles textBox1.KeyDown
    ' 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 OrElse e.KeyCode > Keys.D9 Then
        ' Determine whether the keystroke is a number from the keypad.
        If e.KeyCode < Keys.NumPad0 OrElse e.KeyCode > Keys.NumPad9 Then
            ' Determine whether the keystroke is a backspace.
            If e.KeyCode <> Keys.Back Then
                ' A non-numerical keystroke was pressed. 
                ' Set the flag to true and evaluate in KeyPress event.
                nonNumberEntered = True
            End If
        End If
    End If
    'If shift key was pressed, it's not a number.
    If Control.ModifierKeys = Keys.Shift Then
        nonNumberEntered = true
    End If
End Sub 'textBox1_KeyDown


' This event occurs after the KeyDown event and can be used 
' to prevent characters from entering the control.
Private Sub textBox1_KeyPress(sender As Object, e As System.Windows.Forms.KeyPressEventArgs) _
    Handles textBox1.KeyPress
    ' Check for the flag being set in the KeyDown event.
    If nonNumberEntered = True Then
        ' Stop the character from being entered into the control since it is non-numerical.
        e.Handled = True
    End If
End Sub 'textBox1_KeyPress

Remarques

Le déclenchement d'un événement appelle le gestionnaire des événements par l'intermédiaire d'un délégué.Raising an event invokes the event handler through a delegate. Pour plus d’informations, consultez gestion et déclenchement d’événements.For more information, see Handling and Raising Events.

La méthode OnKeyDown permet également aux classes dérivées de gérer l'événement sans y attacher de délégué.The OnKeyDown method also allows derived classes to handle the event without attaching a delegate. Il s'agit de la méthode recommandée pour gérer l'événement dans une classe dérivée.This is the preferred technique for handling the event in a derived class.

Notes pour les héritiers

Lors de la substitution de OnKeyDown(KeyEventArgs) dans une classe dérivée, veillez à appeler la méthode OnKeyDown(KeyEventArgs) de la classe de base de manière à ce que les délégués inscrits reçoivent l'événement.When overriding OnKeyDown(KeyEventArgs) in a derived class, be sure to call the base class's OnKeyDown(KeyEventArgs) method so that registered delegates receive the event.

S’applique à

Voir aussi