Control.KeyPress Control.KeyPress Control.KeyPress Control.KeyPress Event

Definición

Se produce cuando se presionaOccurs when a character. una tecla de espacio o retroceso mientras el control tiene el foco.space or backspace key is pressed while the control has focus.

public:
 event System::Windows::Forms::KeyPressEventHandler ^ KeyPress;
public event System.Windows.Forms.KeyPressEventHandler KeyPress;
member this.KeyPress : System.Windows.Forms.KeyPressEventHandler 
Public Custom Event KeyPress As KeyPressEventHandler 

Ejemplos

El siguiente ejemplo de código utiliza el KeyPress eventos para evitar que los caracteres de escritura del control.The following code example uses the 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;

   // 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

En el ejemplo de código siguiente se muestra el orden de las crecientes el KeyDown, KeyUp y KeyPress eventos, también cómo registrar los controladores de eventos en ellos.The following code example demonstrates the order of rising the KeyDown, KeyUp and KeyPress events, also how to register event handlers on them.

public partial class Form2 : Form
{
	public Form2()
	{
		InitializeComponent();
		textBox2.Multiline = true;
		textBox2.ScrollBars = ScrollBars.Both;

		//Setup events that listens on keypress
		textBox1.KeyDown += TextBox1_KeyDown;
		textBox1.KeyPress += TextBox1_KeyPress;
		textBox1.KeyUp += TextBox1_KeyUp;
	}

	// Handle the KeyUp event to print the type of character entered into the control.
	private void TextBox1_KeyUp(object sender, KeyEventArgs e)
	{
		textBox2.AppendText( $"KeyUp code: {e.KeyCode}, value: {e.KeyValue}, modifiers: {e.Modifiers}" + "\r\n");
	}

	// Handle the KeyPress event to print the type of character entered into the control.
	private void TextBox1_KeyPress(object sender, KeyPressEventArgs e)
	{
		textBox2.AppendText( $"KeyPress keychar: {e.KeyChar}" + "\r\n");
	}

	// Handle the KeyDown event to print the type of character entered into the control.
	private void TextBox1_KeyDown(object sender, KeyEventArgs e)
	{
		textBox2.AppendText( $"KeyDown code: {e.KeyCode}, value: {e.KeyValue}, modifiers: {e.Modifiers}" + "\r\n");
	}
}
Public Class Form2

    ' Handle the KeyDown event to print the type of character entered into the control.
    Private Sub TextBox1_KeyDown(sender As Object, e As KeyEventArgs) Handles TextBox1.KeyDown
        TextBox2.AppendText($"KeyDown code: {e.KeyCode}, value: {e.KeyValue}, modifiers: {e.Modifiers}" + vbCrLf)
    End Sub

    ' Handle the KeyPress event to print the type of character entered into the control.
    Private Sub TextBox1_KeyPress(sender As Object, e As KeyPressEventArgs) Handles TextBox1.KeyPress
        TextBox2.AppendText($"KeyPress keychar: {e.KeyChar}" + vbCrLf)
    End Sub

    ' Handle the KeyUp event to print the type of character entered into the control.
    Private Sub TextBox1_KeyUp(sender As Object, e As KeyEventArgs) Handles TextBox1.KeyUp
        TextBox2.AppendText($"KeyUp code: {e.KeyCode}, value: {e.KeyValue}, modifiers: {e.Modifiers}" + vbCrLf)
    End Sub

End Class

Comentarios

Se producen eventos claves en el orden siguiente:Key events occur in the following order:

  1. KeyDown

  2. KeyPress

  3. KeyUp

El KeyPress claves no son de caracteres que no sea espacio y retroceso no provoca eventos; sin embargo, las teclas de carácter que no es activan el KeyDown y KeyUp eventos.The KeyPress event is not raised by non-character keys other than space and backspace; however, the non-character keys do raise the KeyDown and KeyUp events.

Use el KeyChar propiedad pulsaciones de teclas de ejemplo en tiempo de ejecución así como para consumir o modificar un subconjunto de pulsaciones de teclas comunes.Use the KeyChar property to sample keystrokes at run time and to consume or modify a subset of common keystrokes.

Para controlar los eventos de teclado sólo en el nivel de formulario y no permitir que otros controles recibir eventos de teclado, establezca el KeyPressEventArgs.Handled propiedad en el formulario KeyPress método de control de eventos para true.To handle keyboard events only at the form level and not enable other controls to receive keyboard events, set the KeyPressEventArgs.Handled property in your form's KeyPress event-handling method to true.

Para obtener más información sobre el manejo de eventos, consulte controlar y provocar eventos.For more information about handling events, see Handling and Raising Events.

Se aplica a

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