c# Detect mouse clicks anywhere (Inside and Outside the Form)

Question

Is this possible to detect a mouse click (Left/Right) anywhere (Inside and Outside the Form) in an if statement? And if it's possible, how?

if(MouseButtons.LeftButton == MouseButtonState.Pressed){

...

}

Answer 1

When user clicks outside the form control, it losses the focus and you can make use of that.which means you have to use the _Deactivate(object sender, EventArgs e) event of the form control to make this work. Since which will trigger when the form loses focus and is no longer the active form . Let Form1 be the form, then the event will be like the following:

private void Form1_Deactivate(object sender, EventArgs e)
{
    // Your code here to handle this event
}

Answer 2

Here is a starter, if I understood your needs of "clicking from outside the window" and Hans Passant's suggestion doesn't fit your needs. You might need to add an event handler for Form1_Click .

CAUTION: This code is provided to illustrate the concept. The threading synchronization in this sample is not 100% correct. Check the history of this answer for an attempt at a more "threading correct" one that sometimes throws exceptions. As an alternative, to get rid of all threading issues, you could have the task in StartWaitingForClickFromOutside be instead always running (aka be always in "listen" mode) as opposed to trying to detect the "within the form" or "outside the form" states and starting/stopping the loop accordingly.

using System;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            this.MouseLeave += Form1_MouseLeave;
            this.Leave += Form1_Leave;
            this.Deactivate += Form1_Deactivate;
            this.MouseEnter += Form1_MouseEnter;
            this.Activated += Form1_Activated;
            this.Enter += Form1_Enter;
            this.VisibleChanged += Form1_VisibleChanged;
        }

        private AutoResetEvent are = new AutoResetEvent(false);

        // You could create just one handler, but this is to show what you need to link to
        private void Form1_MouseLeave(object sender, EventArgs e) => StartWaitingForClickFromOutside();
        private void Form1_Leave(object sender, EventArgs e) => StartWaitingForClickFromOutside();
        private void Form1_Deactivate(object sender, EventArgs e) => StartWaitingForClickFromOutside();
        private void StartWaitingForClickFromOutside()
        {
            are.Reset();
            var ctx = new SynchronizationContext();

            var task = Task.Run(() =>
            {
                while (true)
                {
                    if (are.WaitOne(1)) break;
                    if (MouseButtons == MouseButtons.Left)
                    {
                        ctx.Send(CLickFromOutside, null);
                        // You might need to put in a delay here and not break depending on what you want to accomplish
                        break;
                    }
                }
            });
        }

        private void CLickFromOutside(object state) => MessageBox.Show("Clicked from outside of the window");
        private void Form1_MouseEnter(object sender, EventArgs e) => are.Set();
        private void Form1_Activated(object sender, EventArgs e) => are.Set();
        private void Form1_Enter(object sender, EventArgs e) => are.Set();
        private void Form1_VisibleChanged(object sender, EventArgs e)
        {
            if (Visible) are.Set();
            else StartWaitingForClickFromOutside();
        }
    }
}

If I understood you incorrectly, you might find this useful: Pass click event of child control to the parent control

Answer 3

One method is to cover the entire screen with a borderless form with the properties set to transparent (a few percent above completely transparent, not sure if total transparency works but you won't notice the difference) and also set to topmost. Then use the events from the form. As soon as a click is detected this will not affect anything underneath the form (which in my application is something I want to happen) but the form could be closed and another mouse click simulated a fraction of a second later to activate the controls that are underneath. I had no problem using the windows API to use mouse hooks in VB6 but cannot seem to find something that works in c# with the 2019 version of .NET so this is a good workaround. Of course to be really clever you could use an irregular forms method to make the transparent form the same shape as the mouse and follow it. Note: I have just found the complete code to do it using hooks that mere mortals can get up and running at once! KeyboardMouseHooks C# Library - CodePlex Archive PS if you use my (dumb) method remember to create an escape key or button or you will have to restart your computer unless the form is programmed to disappear for real clicks as suggested!

Answer 4

I know this is late but maybe it helps someone. Using the MouseEventArgs of the MouseUp event of any control you can check for mouse button and wheel among other things. Here is an example.

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        this.MouseUp += Form1_MouseUp;
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
        if(e.Button == MouseButtons.Left)
        {
            DoSomething_LeftClick();
        }
        else if(e.Button == MouseButtons.Right)
        {
            DoSomething_RightClick();
        }
    }

    private void DoSomething_LeftClick()
    {
        //Here some code
    }
    private void DoSomething_RightClick()
    {
        //Here some code
    }
}