Paint event not fired

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I'm trying to draw lines on a picturebox object on my form by calling a paintevent as follow:

C#

private void button3_Click(object sender, EventArgs e)
{
      this.pictureBox1.Paint += new
      System.Windows.Forms.PaintEventHandler(this.pictureBox1_Paint);

}

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
     ......code...
}

but for some reason the paint event isn't fired, although I used simular code in other projects.

Can someone advise if I missed something?

What I have tried:

I have added a Breakpoint in the paint event, but in debug mode this breakpoint isn't hit.
I also put a MessageBox.Show event in the paint event, but with no result.
Using pictureBox1.Invalidate() didn't work either.

The above made me conclude that the paint event wasn't fired

Posted 31-Aug-21 21:37pm

Member 11336683

Updated 1-Sep-21 2:43am

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Dave Kreskowiak · Accepted Answer · 2021-09-01T02:43:00

Why on earth are you wiring up the Paint event handler in a button Click handler? That should be wired up once, usually when the app starts.

You can then call your PictureBox.Invalidate method in the Click event handler to get the PictureBox to repaint.

Wiring up an event handler over and over again does nothing for you. It does NOT fire the Paint event.

OriginalGriff · Accepted Answer · 2021-08-31T21:51:00

Check that the button click event is fired: put a breakpoint there and check the handler is added (though adding a handler each time the button is clicked is a bad idea).

The most likely reason for a Paint handler not firing is it isn't hooked up, and that implies that the button event isn't hooked up either, or it's all hooked to the wrong instance of the form.

When you are sure it is attached, check that the PictureBox itself is Invalidated at some point - Paint is only raised when it's needed, it isn't on a timer or anything.

Quote:
Hi OriginalGriff, done it all. The button click is fired, but the paint event is not hit. Invalidate the picturebox doesn't help either.
I'm a bit lost here

All I can say is "it works fine for me":

C#

private void button1_Click(object sender, EventArgs e)
    {
    pictureBox1.Paint += new PaintEventHandler(PictureBox1_Paint);
    }

private void PictureBox1_Paint(object sender, PaintEventArgs e)
    {
    e.Graphics.DrawRectangle(Pens.Green, new Rectangle(5, 5, pictureBox1.Width - 10, pictureBox1.Height - 10));
    }

private void button2_Click(object sender, EventArgs e)
    {
    pictureBox1.Invalidate();
    }

Paint event not fired

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Paint event not fired

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