How to detect modifier key states in WPF?

Question

Is there some global constructs that I can use whenever I need to access whether the Control, Shift, Alt buttons are down? For instance inside MouseDown event of a TreeView.

If so how?

kyrylomyr · Accepted Answer · 2011-04-21T23:16:27.653

Use class Keyboard. Using Keyboard.IsKeyDown you can check if Control, Shift, Alt is down now.

For Shift:

if (Keyboard.IsKeyDown(Key.LeftShift) || Keyboard.IsKeyDown(Key.RightShift))
{ /* Your code */ }

For Control:

if (Keyboard.IsKeyDown(Key.LeftCtrl) || Keyboard.IsKeyDown(Key.RightCtrl))
{ /* Your code */ }

For Alt:

if (Keyboard.IsKeyDown(Key.LeftAlt) || Keyboard.IsKeyDown(Key.RightAlt))
{ /* Your code */ }

score 136 · Answer 2 · answered Apr 21 '11 at 23:23

136

There's also:

// Have to get this value before opening a dialog, or user will have released the control key
if ((Keyboard.Modifiers & ModifierKeys.Control) == ModifierKeys.Control)
{

}

answered Apr 21 '11 at 23:23

Chuck Savage

11,775
6
49
69

13

Much better solution. It also allows you to check all modifiers at once. If you want to handle Ctrl+F, you won't want to handle Ctrl+Shift+F, so you could just check for `(e.Key == Key.F && e.KeyboardDevice.Modifiers == ModifierKeys.Control)` instead of all the other stuff... – ygoe Mar 08 '13 at 19:18
36

Note that the comparisons in the examples above produces different results! As the ModifierKeys enum has the Flags attribute you can can have any combinations of values in the enum. If you want to catch ONLY the shift key being pressed, use the `Keyboard.Modifiers == ModifierKeys.Shift` statement. If you want to catch the shift key but dont care if other modifiers are pressed at the same time, use the `(Keyboard.Modifiers & ModifierKeys.Shift) == ModifierKeys.Shift` or the much better HasFlag syntax `Keyboard.Modifiers.HasFlag(ModifierKeys.Shift)` – Patrik B Aug 27 '13 at 08:48
4

I could not catch the windows key modifier using this method. (CTRL worked fine.) I was trying to catch `WIN+RightArrow`. – ANeves May 06 '14 at 19:15
1

@ANeves Interesting, `Keyboard.Modifiers` shows as `None` – Chuck Savage May 07 '14 at 00:34

score 9 · Answer 3 · edited Sep 02 '15 at 10:14

9

    private bool IsShiftKey { get; set; }

    private void OnPreviewKeyDown(object sender, KeyEventArgs e)
    {
        IsShiftKey = Keyboard.Modifiers == ModifierKeys.Shift ? true : false;

        if ((Key.Oem3 == e.Key || ((IsShiftKey && Key.Oem4 == e.Key) || (IsShiftKey && Key.Oem6 == e.Key) || (IsShiftKey && Key.Oem5 == e.Key)) && (validatorDefn as FormatValidatorDefinition).format == "packedascii"))
        {
           e.Handled = true;
        }
    }

edited Sep 02 '15 at 10:14

Ciaran Martin

578
4
12

answered Sep 18 '14 at 16:06

Krushik

97
1
1

2

Answers are better with commentary as well as code. Please provide some context. – ChrisGPT was on strike Sep 18 '14 at 16:25
1

great idea of adding it as an proprerty – RollRoll Aug 24 '17 at 13:28
1

When I used PreviewKeyDown looking for Alt + another key I had to use e.SystemKey instead of e.Key (e.Key's value was "System" in the case of using alt+another character, in my case) – Josh Nov 08 '18 at 16:52

score 5 · Answer 4 · answered Nov 08 '18 at 16:56

This is how I handle it (using PreviewKeyDown), let's say we are looking for Alt + R...

private void OnPreviewKeyDown(object sender, KeyEventArgs e)
{
    if ((Keyboard.IsKeyDown(Key.LeftAlt) || Keyboard.IsKeyDown(Key.RightAlt)
       && e.SystemKey == Key.R)
    {
       //do whatever
    }
}

Maybe someone can clear up why I had to use e.SystemKey and not just e.Key, maybe due to the modifier? but this has worked flawlessly for me when searching for modifier+key.

score 5 · Answer 5 · answered May 06 '20 at 05:57

Partly borrowing from @Josh, and somewhat similar to @Krushik, and also referencing a question about the Difference between KeyEventArgs.systemKey and KeyEventArgs.Key (answering why Josh has to use SystemKey); wherein, with modifier keys (such as Alt), e.Key returns Key.System, and thus the 'real' key is within e.SystemKey.

A way around this, is to first fetch the 'real' key, and then do your conditional:

private void OnPreviewKeyDown(object sender, KeyEventArgs e)
{
    // Fetch the real key.
    var key = e.Key == Key.System ? e.SystemKey : e.Key;

    if ((Keyboard.IsKeyDown(Key.LeftAlt) || Keyboard.IsKeyDown(Key.RightAlt))
        && key == Key.Return)
    {
        // Execute your code.
    }
}

Thanks for the answer to the question embedded in my answer ;) I never actually looked it up, good to know! — Josh, Aug 19 '20 at 17:32

score -1 · Answer 6 · answered May 07 '18 at 00:48

-1

and as well:

if My.Computer.Keyboard.ShiftKeyDown then ...

My.Computer.Keyboard.CtrlKeyDown

My.Computer.Keyboard.AltKeyDown

answered May 07 '18 at 00:48

Rob

3,488
3
32
27

How to detect modifier key states in WPF?

6 Answers6

Linked