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Control.KeyPress Event

Occurs when a key is pressed while the control has focus.

[Visual Basic]
Public Event KeyPress As KeyPressEventHandler
[C#]
public event KeyPressEventHandler KeyPress;
[C++]
public: __event KeyPressEventHandler* KeyPress;

[JScript] In JScript, you can handle the events defined by a class, but you cannot define your own.

Event Data

The event handler receives an argument of type KeyPressEventArgs containing data related to this event. The following KeyPressEventArgs properties provide information specific to this event.

Property Description
Handled Gets or sets a value indicating whether the KeyPress event was handled.
KeyChar Gets the character corresponding to the key pressed.

Remarks

Key events occur in the following order:

  1. KeyDown
  2. KeyPress
  3. KeyUp

The KeyPress event is not raised by noncharacter keys; however, the noncharacter keys do raise the KeyDown and KeyUp events.

To handle keyboard events only at the form level and not allow other controls to receive keyboard events, set the KeyPressEventArgs.Handled property in your form's KeyPress event-handling method to true.

For more information about handling events, see Consuming Events.

.NET Compact Framework Platform Note:  In addtion to the base Control class, the .NET Compact Framework provides support for this event on controls with Service Pack 2 and later. The Smart Devices Developer Community Web site provides information about the availability of service packs, see http://go.microsoft.com/fwlink/?LinkId=16561.

Example

[Visual Basic] 
' 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 

[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;
            }
        }
    }
}

// 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;
    }
}


[C++] 
// 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;
         }
      }
   }
}

// 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;
   }
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also

Control Class | Control Members | System.Windows.Forms Namespace | OnKeyPress

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