nothing is being drawn in the forms paint event

  • Thread starter Thread starter Tony Johansson
  • Start date Start date
T

Tony Johansson

Hello!

Here I have a piece of code that doesn't draw anything when I have the code
marked with 1 but works perfect when I use the code that is marked with 2.
Can somebody explain that ?

private void Form1_Paint(object sender, PaintEventArgs e)
{
1 Bitmap bm = new Bitmap(600, 600);
1 Graphics g = Graphics.FromImage(bm);

2 Graphics g = this.CreateGraphics();

Brush b = new LinearGradientBrush(new Point(1, 1), new Point(600,
600),
Color.White, Color.Red);
Point[] points = new Point[] {new Point(10,10),
new Point(77,500),
new Point(590, 100),
new Point(250,590),
new Point(300,410)};
g.FillPolygon(b, points);
g.DrawPolygon(new Pen(Color.Red, 7), points);
}

//Tony
 
Hello!

Here I have a piece of code that doesn't draw anything when I have the code
marked with 1 but works perfect when I use the code that is marked with 2.
Can somebody explain that ?

private void Form1_Paint(object sender, PaintEventArgs e)
{
1 Bitmap bm = new Bitmap(600, 600);
1 Graphics g = Graphics.FromImage(bm);
Click to expand...

You are drawing on the bitmap, so nothing will be drawn on the form.
2 Graphics g = this.CreateGraphics();
Click to expand...

Don't do that. Use

Graphics g = e.Graphics;

instead.
 
2 Graphics g = this.CreateGraphics();
Click to expand...

Clearly you didn't follow that link to Bob Powell's site I gave you in the
other thread or you'd know that CreateGraphics() is almost never what you
want.

Seriously, go to Bob's site. His FAQ will cover just about every pitfall
you're going to stumble into as you learn about GDI+ graphics in .NET.
 
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