GDI+ FillPolygon()

Jeg har en figur som jeg ønsker at fylde med farve.

Men jeg kan ikke rigtig få metoden FillPolygon til at virke.
(Graphics.FillPolygon())



Figuren ser sådan her ud:

    System.Drawing.Graphics formGraphics = null;
            System.Drawing.Pen myPen;

            formGraphics = pictureBox8.CreateGraphics();
            myPen = new System.Drawing.Pen(System.Drawing.Color.Black,1);
            formGraphics.DrawLine(myPen, 5, 20, 90, 20);
            formGraphics.DrawLine(myPen, 5, 20, 5, 90);
            formGraphics.DrawLine(myPen, 90, 20, 90, 90);

            formGraphics.DrawLine(myPen, 5,90,30,115);
            formGraphics.DrawLine(myPen, 90, 90, 65, 115);
            formGraphics.DrawLine(myPen, 30, 115, 65, 115);
            myPen.Dispose();





Men når jeg fylder farve i den, så virker det ikke:

        SolidBrush GrayBrush = new SolidBrush(Color.Gray);
            Point point1 = new Point(5, 20);
            Point point2 = new Point(90, 20);
            Point point3 = new Point(5, 20);
            Point point4 = new Point(5, 90);
            Point point5 = new Point(90, 20);
            Point point6 = new Point(90, 90);
            Point point7 = new Point(5, 90);
            Point point8 = new Point(90, 90);
           
            Point[] curvePoints = new Point[]
            {
                point1,
                point2,
                point3,
                point4,
                point5,
                point6,
                point7,
                point8
            };

           
            formGraphics.FillPolygon(GrayBrush, curvePoints);
           


Nogen ideer?