KeyEventArgs.Handled Property

Definition

Namespace:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Source:

KeyEventArgs.cs

Gets or sets a value indicating whether the event was handled.

C#

public bool Handled { get; set; }

Property Value

Boolean

true to bypass the control's default handling; otherwise, false to also pass the event along to the default control handler.

Examples

The following example determines whether the user pressed a non-numeric key, and if so, cancels the KeyPress event by using the Handled property.

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;
            }
        }
    }
    //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)
    {
        // Stop the character from being entered into the control since it is non-numerical.
        e.Handled = true;
    }
}

Remarks

Handled is implemented differently by different controls within Windows Forms. For controls like TextBox which subclass native Win32 controls, it is interpreted to mean that the key message should not be passed to the underlying native control. If you set Handled to true on a TextBox, that control will not pass the key press events to the underlying Win32 text box control, but it will still display the characters that the user typed.

If you want to prevent the current control from receiving a key press, use the SuppressKeyPress property.

Applies to

See also

• SuppressKeyPress