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Control.OnKeyPress Method

Raises the KeyPress event.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)

'Declaration
Protected Overridable Sub OnKeyPress ( _
	e As KeyPressEventArgs _
)
'Usage
Dim e As KeyPressEventArgs

Me.OnKeyPress(e)
protected void OnKeyPress (
	KeyPressEventArgs e
)
protected function OnKeyPress (
	e : KeyPressEventArgs
)
Not applicable.

Parameters

e

A KeyPressEventArgs that contains the event data.

Raising an event invokes the event handler through a delegate. For more information, see Raising an Event.

The OnKeyPress 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.

Notes to Inheritors: When overriding OnKeyPress in a derived class, be sure to call the base class's OnKeyPress method so that registered delegates receive the event.

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 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
    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
End Class 'Form1 

// 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

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

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0
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