The following example creates a 
GraphicsPath object 
path, adds a line to 
path, and then draws path.
C++
VOID Example_AddLine(HDC hdc)
{
   Graphics graphics(hdc);
   GraphicsPath path;
   path.AddLine(20.0f, 20.0f, 100.0f, 100.0f);
   // Draw the path.
   Pen pen(Color(255, 255, 0, 0));
   graphics.DrawPath(&pen, &path);
}
SUB GDIP_AddPathLine (BYVAL hdc AS DWORD)
   LOCAL hStatus AS LONG
   LOCAL pGraphics AS DWORD
   LOCAL pPath AS DWORD
   LOCAL pPen AS DWORD
   hStatus = GdipCreateFromHDC(hdc, pGraphics)
   hStatus = GdipCreatePath(%FillModeAlternate, pPath)
   hStatus = GdipAddPathLine(pPath, 20, 20, 100, 100)
   ' // Draw the path.
   hStatus = GdipCreatePen1(GDIP_ARGB(255, 255, 0, 0), 1, %UnitWorld, pPen)
   hStatus = GdipDrawPath(pGraphics, pPen, pPath)
   ' // Cleanup
   IF pPen THEN GdipDeletePen(pPen)
   IF pPath THEN GdipDeletePath(pPath)
   IF pGraphics THEN GdipDeleteGraphics(pGraphics)
END SUB
(http://www.jose.it-berater.org/captures/GdipAddPathLine.png)