Invalidate picturebox with rectangle on

[Dumpen]

Hello.

I have a simple picturebox where there is a image loaded in

Im drawing a rectangle on the picturebox and when I press a button I want to invalidate it (remove the rectangle), but it doesnt seem to work

The rectangle is drawn fine and the image loads up to, but when I press my button nothing happens

Here is the code im using:

        private void drawOnPic()
        {
            // Attach grapich to picturebox
            Graphics g = Graphics.FromImage(pictureBox1.Image);

            // Create a new pen that we shall use for drawing the line
            Pen PenStyle = new Pen(Color.Red, 1);

            // Draw a 50x50 pixels rectangle (x, y, width, hight)
            g.DrawRectangle(PenStyle, 20, 20, 50, 50);
        }

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

        private void Form1_Load(object sender, EventArgs e)
        {
            drawOnPic();
        }

[mckee.kyle]

Hey Dumpen,
I haven't really used the System.Drawing stuff very much....but here's what I found.

When I copied and pasted your code, the rectangle never showed up. To get the rectangle to show up I changed two things. I changed the graphics object, and I had to move the call to the draw method outside of the form's load event (I moved it to a button for simplicity).

After I changed that I think it functioned the way you were expecting. One button would draw the rectangle and the other would invalidate it causing it to repaint without the rectangle.

       private void drawOnPic()
        {
            // Attach grapich to picturebox
            Graphics g = pictureBox1.CreateGraphics();  //I changed this.
            
            // Create a new pen that we shall use for drawing the line
            Pen PenStyle = new Pen(Color.Red, 1);

            // Draw a 50x50 pixels rectangle (x, y, width, hight)
            g.DrawRectangle(PenStyle, 20, 20, 50, 50);
           
        }

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

        private void button2_Click(object sender, EventArgs e)
        {
            drawOnPic(); //I moved the call to this method from the form's load to this button's eventhandler.
        }

        private void Form1_Load(object sender, EventArgs e)
        { }

Someone else who actually knows what they're doing can probably help a lot more, I'm just shooting in the dark!