C# WindowsForms - Hide control after clicking outside of it

Question

C# WindowsForms - Hide control after clicking outside of it

I have a picturebox (fe picturebox1) which is not visible as default. When I click a button (let's say button1) the picturebox1 will show up. Now -> I need the picturebox1 to become hidden again when I click outside of it (on form itself or any other control). It works the same as a contextmenu would work.

I have no idea how to do it since any "Click_Outside" event doesn't exist. Is there any simple way to do this? Thanks.

Answer 1

Here is a simple solution, albeit not one that is totally easy to fully understand as it does involve catching the WndProc event and using a few constants from the Windows inderds..:

This is the obvious part:

private void button1_Click(object sender, EventArgs e)
{
    pictureBox1.Show();
}

Unfortunately we can't use the pictureBox1.LostFocus event to hide the Picturebox .

That is because only some controls can actually receive focus when clicking them; a Button or other interactive controls like a ListBox , a CheckBox etc can, too.

But a Panel , a PictureBox and also the Form itself can't receive focus this way. So we need a more global solution.

As ever so often the solution comes form the depths of the Windows message system:

const int WM_PARENTNOTIFY = 0x210;
const int WM_LBUTTONDOWN = 0x201;

protected override void WndProc(ref Message m)
{
    if (m.Msg == WM_LBUTTONDOWN || (m.Msg == WM_PARENTNOTIFY && 
        (int)m.WParam == WM_LBUTTONDOWN))
        if (!pictureBox1.ClientRectangle.Contains( 
                         pictureBox1.PointToClient(Cursor.Position))) 
            pictureBox1.Hide();
    base.WndProc(ref m);
}

Note that we need to make sure that you can still clcik on the PictureBox itself; so we check if the mouse is inside its ClientRectangle ..

Simply add this to the form code and every click outside the PictureBox will hide it.

Answer 2

使用控件的LostFocus事件（在您的情况下，是一个PictureBox控件）

Answer 3

As you said, the ClickOutside doesn't exist, so you have few choices:

Loop through all the controls of your form (Form.Controls) and add a click event that hides the PictureBox excluding your "Show" button.

You can intercept the mouse click message at the source like in this example: intercept

Answer 4

The easiest way is this: Copy and paste the following method anywhere in your code:

private void mouseClick(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left && pictureBox1.Visible == true)
            pictureBox1.Visible = false;
    }

then inside your form_Load Event copy and paste the following code:

foreach (Control ctrl in this.Controls)
    if (ctrl is GroupBox || ctrl is .....)
        ctrl.MouseClick += mouseClick;

of course you should repeat this loop for every groupBox within another groupBox and replace the dots with textbox, button, combobox, label, ... according to what controls you have