public void DrawLine(GDIPen pen, Point p1, Point p2)
{
IntPtr oldpen = NativeMethods.SelectObject(mhDC, pen.hPen);
APIPoint gp;
gp.x = 0;
gp.y = 0;
NativeMethods.MoveToEx(mhDC, p1.X, p1.Y, ref gp);
NativeMethods.LineTo(mhDC, p2.X, p2.Y);
NativeMethods.SelectObject(mhDC, oldpen);
}