Detecting Ctrl+Left (mouse button) in MouseDown event handler

Question

When I first press down control key (the left one) and then click the left mouse button, why does the following code gets executed. I am modifying existing code and the below code is already there. I guess no one has tried it before, with control key pressed, it has only been used with left-mouse-clicked and it has always worked for that case. But I want a different code executed when the mouse left key is pressed at the same time that the control key is pressed.

private void treeList1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
    TreeList tree = sender as TreeList;

    if (e.Button == MouseButtons.Right && ModifierKeys == Keys.None && tree.State == TreeListState.Regular)
    {
       //the code that is here gets executed 
       MessageBox.Show("I am here");
    }
}

I would highly appreciate any hint or help.

P.S. I would like to add that in the above case when I inspect e.button value it shows that is equal to Right although I pressed the left mouse button and the Ctrl Key. That is a mystery to me.

Dear StackOverflow fellows :I found the problem, since I am using a VM on a MAC I had to disable some Key Mapping on my Virtual Machine preference and now my original code works. Thanks for all your help.

What does ModifierKeys contain on debug? It is obvious it does not contain Control. — nzic, Feb 18 '13 at 23:26
Is this .net 4.0? This might help: http://stackoverflow.com/questions/4705428/test-if-the-ctrl-key-is-down-using-c-sharp — Mathieu Guindon, Feb 18 '13 at 23:36
The event gets fired as expected and you're certain that the `msgbox` code gets executed? — Jeremy Thompson, Feb 18 '13 at 23:53
@retailcoder it is .net4 and the link did not help. Thanks anyway. — user1298925, Feb 19 '13 at 04:12

Mathieu Guindon · Answer 1 · 2013-02-19T04:37:44.223

Keys.None has a value of 0, making it hard to detect when "no key is pressed" when used alone. This:

    void Form1_MouseDown(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left && (ModifierKeys & Keys.None) == Keys.None)
        {
            MessageBox.Show("No key was held down.");
        }
    }

Will pop a message box whatever the key combination is, as long as the click occurs with the left button.

However, this:

    void Form1_MouseDown(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left && (ModifierKeys & Keys.Control) == Keys.Control)
        {
            MessageBox.Show("Control key was held down.");
        }
    }

Will only pop a message box when the Control key is held down (and the left mouse button is clicked).

Try reversing your conditions and detect when the Control key is pressed when clicking (instead of detecting when no key is pressed). That being said I'm having a hard time getting the same code to work with Keys.ControlKey or Keys.LControlKey for some reason, so isolating the left control key needs a little more research.

I tried your first box of code, it does not work. Can you please edit what is needed after e. Maybe I am filling the blanks that you have with wrong value. So, I still dont have any answer. Still when I click the left mouse button with the ctrl down it executes the code for right mouse click! I have not tried your second box yet. Thanks. — user1298925, Feb 19 '13 at 04:11
I tried this code (second code-block) - it works! Thank you, @Mat'sMug! :) — V. Panchenko, Jan 09 '16 at 12:40
I'm a bit late but since .Net 4.0 (at least) enums have `HasFlag` method for checking if certain bits are set. — Emperor Orionii, May 28 '19 at 08:50

score -1 · Accepted Answer · answered Feb 19 '13 at 16:06

-1

The problem was that there was a key mapping between MAC and my Windows Virtual Machine that needed to be disabled. Thanks for all the help

answered Feb 19 '13 at 16:06

user1298925

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Interesting. Have you reversed the condition or trapping `Keys.None` worked? – Mathieu Guindon Feb 19 '13 at 16:47
Have not tried that yet, I will and I will definitely let you know. Thanks again. – user1298925 Feb 19 '13 at 18:00

Detecting Ctrl+Left (mouse button) in MouseDown event handler

2 Answers2