Test if the Ctrl key is down using C#

Question

I have a form that the user can double click on with the mouse and it will do something. Now I want to be able to know if the user is also holding the Ctrl key down as the user double click on the form.

How can I tell if the user is holding the Ctrl key down?

http://stackoverflow.com/questions/973721/c-detecting-if-the-shift-key-is-held-when-opening-a-context-menu This is for the Shiftkey. But the concept is the same. — LiamB, Jan 16 '11 at 12:54
IMO, It's a messy concept when we have predefined elements in place to aid us here, without resorting to less maintainable 'magic numbers'. — Grant Thomas, Jan 16 '11 at 12:59
@GrantThomas I'm sure he was referring to the answers in that thread, which provide exactly what you provided above aside from being a different modifier key. — Dan Bechard, Nov 06 '12 at 14:24
@Dan Possibly, but in hindsight this is just comment-worthy, unless he wishes to copypasta from there and duplicate. — Grant Thomas, Nov 06 '12 at 14:26

score 116 · Accepted Answer · answered Jan 16 '11 at 12:57

116

Using .NET 4 you can use something as simple as:

    private void Control_DoubleClick(object sender, EventArgs e)
    {
        if (ModifierKeys.HasFlag(Keys.Control))
        {
            MessageBox.Show("Ctrl is pressed!");
        }
    }

If you're not using .NET 4, then the availability of Enum.HasFlag is revoked, but to achieve the same result in previous versions:

    private void CustomFormControl_DoubleClick(object sender, EventArgs e)
    {
        if ((ModifierKeys & Keys.Control) == Keys.Control)
        {
            MessageBox.Show("Ctrl is pressed!");
        }
    }

answered Jan 16 '11 at 12:57

Grant Thomas

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Maybe, but if that's not possible then my second example still ought to do the trick. – Grant Thomas Jan 16 '11 at 13:08
Enum.HasFlag is about 16 times slower than using the bitwise operation. [stackoverflow.com/questions/7368652](http://stackoverflow.com/questions/7368652/what-is-it-that-makes-enum-hasflag-so-slow) – NET3 Nov 19 '12 at 12:24
That's a reasonable consideration, but isn't always one. – Grant Thomas Nov 19 '12 at 13:08

score 41 · Answer 2 · edited Feb 09 '17 at 11:15

41

Just for completeness... ModifierKeys is a static property of Control, so you can test it even when you are not directly in an event handler:

public static bool IsControlDown()
{
    return (Control.ModifierKeys & Keys.Control) == Keys.Control;
}

edited Feb 09 '17 at 11:15

Irshad

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answered Jan 14 '15 at 09:02

Rob

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This is a *Very* important point to note, in the case you are trying to do this check in code that does not reside directly in a form. – eidylon Mar 19 '18 at 17:29
Why in particular? – Rob Mar 20 '18 at 18:53
In my case, I'm writing a code-behind dll for a plugin in a third party system. Their entire UI framework for their plugins is all web based though, not Windows controls... so even though my code is in a "form", it doesn't have normal access to the usual Windows Forms properties. As a result I cannot just call ModifierKeys; I need to prefix it with the `Control.` qualifier. – eidylon Mar 20 '18 at 19:56

score 13 · Answer 3 · answered Sep 30 '18 at 04:58

This isn't really an answer to the question at hand, but I needed to do this in a console application and the detail was a little different.

I had to add references to WindowsBase and PresentationFramework, and at that point I could do:

if (System.Windows.Input.Keyboard.Modifiers == ModifierKeys.Control)
   blah

Just adding this here in case someone else is doing something similar.

score 7 · Answer 4 · edited Nov 19 '12 at 09:06

7

Even this also

 private void Control_MouseDoubleClick(object sender, MouseEventArgs e)
    {
        if (ModifierKeys == Keys.Control)
            MessageBox.Show("with CTRL");
    }

edited Nov 19 '12 at 09:06

Echilon

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answered Jan 16 '11 at 13:01

Javed Akram

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score 4 · Answer 5 · answered Jul 26 '19 at 07:05

4

This works for me:

 if(Keyboard.IsKeyDown(Key.LeftCtrl))
    {}

And add references to PresentationCore and WindowsBase

answered Jul 26 '19 at 07:05

bar-tech

41
3

this works, the other suggestions didnt work, syntax problems. – Ted Aug 13 '20 at 08:47
3

This solution is for WPF, not WinForms. – philu Aug 28 '20 at 03:27

score 2 · Answer 6 · answered Jan 31 '17 at 19:01

2

The same soneone said above, but comparing as different than zero, which should be a little faster and use less instructions on most architectures:

public static bool IsControlDown()
{
    return (Control.ModifierKeys & Keys.Control) != 0;
}

answered Jan 31 '17 at 19:01

user1489240

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Test if the Ctrl key is down using C#

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