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PreviewKeyDown Event

Control.PreviewKeyDown Event

Updated: September 2010

Occurs before the KeyDown event when a key is pressed while focus is on this control.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

public event PreviewKeyDownEventHandler PreviewKeyDown

Some key presses, such as the TAB, RETURN, ESC, and arrow keys, are typically ignored by some controls because they are not considered input key presses. For example, by default, a Button control ignores the arrow keys. Pressing the arrow keys typically causes the focus to move to the previous or next control. The arrow keys are considered navigation keys and pressing these keys typically do not raise the KeyDown event for a Button. However, pressing the arrow keys for a Button does raise the PreviewKeyDown event. By handling the PreviewKeyDown event for a Button and setting the IsInputKey property to true, you can raise the KeyDown event when the arrow keys are pressed. However, if you handle the arrow keys, the focus will no longer move to the previous or next control.

For more information about handling events, see Consuming Events.

The following code example demonstrates a Button that includes a ContextMenuStrip. When the Button has the focus and you press the UP ARROW or DOWN ARROW keys, the ContextMenuStrip appears. The PreviewKeyDown event handler detects when the UP ARROW or DOWN ARROW keys are pressed and sets the IsInputKey property to true. This raises the KeyDown event so that you can display the ContextMenuStrip. You should not put any logic in the PreviewKeyDown event handler, other than to set the IsInputKey property. Instead, you should put your logic in the KeyDown event handler.

public Form1()

    // Form that has a button on it
    button1.PreviewKeyDown +=new PreviewKeyDownEventHandler(button1_PreviewKeyDown);
    button1.KeyDown += new KeyEventHandler(button1_KeyDown);
    button1.ContextMenuStrip = new ContextMenuStrip();
    // Add items to ContextMenuStrip

// By default, KeyDown does not fire for the ARROW keys 
void button1_KeyDown(object sender, KeyEventArgs e)
    switch (e.KeyCode)
        case Keys.Down:
        case Keys.Up:
            if (button1.ContextMenuStrip != null)
                    new Point(0, button1.Height), ToolStripDropDownDirection.BelowRight);

// PreviewKeyDown is where you preview the key. 
// Do not put any logic here, instead use the 
// KeyDown event after setting IsInputKey to true. 
private void button1_PreviewKeyDown(object sender, PreviewKeyDownEventArgs e)
    switch (e.KeyCode)
        case Keys.Down:
        case Keys.Up:
            e.IsInputKey = true;

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0




September 2010

Added more explanation and another code example.

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