Question

I have the following code:

int a = 0;
    protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
    {

       base.OnPaint(e);         


        this.Rows[1].Cells[1].Value = a += 1;
    }

and I can see that the variable increases to infinity. I’m using it to paint a graphic making an instance of it and it works fine.
Is this normal? I am creating infinite graph instance? Or I have a problem and I don’t know

Answer 1

When you change the value, the grid needs to re-Paint itself., thus firing the Paint event again and re-executing your code.
This behavior is by design.

In general, you should never change external state in a Paint handler; drawing code should be idempotent (other than the provided Graphics).
Paint events are unpredicable and will fire very often.