The following example creates an array of real numbers. The code then creates a 
Pen object, sets the dash pattern based on the array, and then draws the custom dashed line.
C++
VOID Example_SetDashPattern(HDC hdc)
{
   Graphics graphics(hdc);
   // Create and set an array of real numbers.
   REAL dashVals[4] = {
      5.0f,   // dash length 5
      2.0f,   // space length 2
      15.0f,  // dash length 15
      4.0f};  // space length 4
   // Create a Pen object.
   Pen pen(Color(255, 0, 0, 0), 5);
   // Set the dash pattern for the custom dashed line.
   pen.SetDashPattern(dashVals, 4);
   // Draw the custom dashed line.
   graphics.DrawLine(&pen, 5, 20, 405, 200); 
}
SUB GDIP_SetPenDashArray (BYVAL hdc AS DWORD)
   LOCAL hStatus AS LONG
   LOCAL pGraphics AS DWORD
   LOCAL pPen AS DWORD
   hStatus = GdipCreateFromHDC(hdc, pGraphics)
   ' // Create and set an array of real numbers.
   DIM dashVals(3) AS SINGLE
   ARRAY ASSIGN dashVals() = 5.0!, 2.0!, 15.0!, 4.0!
   ' // Create a Pen object.
   hStatus = GdipCreatePen1(GDIP_ARGB(255, 0, 0, 0), 5, %UnitWorld, pPen)
   ' // Set the dash pattern for the custom dashed line.
   hStatus = GdipSetPenDashArray(pPen, dashVals(0), 4)
   ' // Draw the custom dashed line.
   hStatus = GdipDrawLineI(pGraphics, pPen, 5, 20, 405, 200)
   ' // Cleanup
   IF pPen THEN GdipDeletePen(pPen)
   IF pGraphics THEN GdipDeleteGraphics(pGraphics)
END SUB
(http://www.jose.it-berater.org/captures/GdipSetPenDashArray.png)