GDI+ Generic error on This.Close()?

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C++

C#

GDI+

Ok, so I have a method inside which I cannot use This.close for it always crashes. The main operational block of the method is lower. Inside my method, all other things are mainly declarations or calls to other methods. Any ideas?

for (int i = 0; i < Metode.DESCHIDERI.Length; i++)
{
    int j = Metode.DESCHIDERI[i];

    p2 = new Point((marginiDeschideri[j * 2].X+marginiDeschideri[j*2+1].X)/2, p1.Y);
    Point pp1 = p1;
    Point pp2 = new Point(p2.X + Convert.ToInt16(LSUPRA), p2.Y);
    if ((pp1.X - pp2.X) > L)
    {
        gbmp.Dispose();
        this.Close();
    }
    else
    {
        gbmp.DrawLine(myPen, pp1, pp2);
        if (s == 0)
            s = 10;
        else
            s = -10;
        p1 = new Point(p2.X - Convert.ToInt16(LSUPRA), p2.Y + s);
    }
}

EDIT: It seems to me I have a problem with this.close() because it does not stop execution. For instance, under debug mode, I can see it clearly going over to this.close() and then over to the next instructions like nothing happened.
EDIT: Wherever I put this.close() inside this method, or others, I get the error.