CreateGraphics() Method and Paint Event Args

Question

I have read somewhere that CreateGraphics() will do this steps for us :

1. BeginPaint
2. Drawing
3. EndPaint

I have my code like this :

private void Form1_Load(object sender, EventArgs e)
{
    grFrom = this.CreateGraphics();
    grFrom.FillRectangle(Brushes.Red, this.ClientRectangle);
}

There is no red rectangle...but, When I copy line below in Form1_paint, every thing runs correctly.

grFrom.FillRectangle(Brushes.Red, this.ClientRectangle);

So Question is Here: What is the e.Graphics in Form1_paint?

CreateGraphics or e.Graphics?

Answer 1

Two things:

1. CreateGraphics gives you a graphics object that you should always Dispose() prior to exiting. You should put your statement inside of a using block.
2. The graphics you draw are only valid until the form gets repainted. In your case, by calling this in Form_Load, it's happening prior to the first render, and getting "thrown away". You should always put this in OnPaint() in order to have it "persistent" on the screen, as that will cause it to get redrawn when the control is redrawn.