C# slow drawing a lot of lines : I want to draw a lot of lines in 3 forms, but when i call this (code):

the form spend a lot of time, with 200+ lines spend 1 sec aprox, what i doing wrong?

    public void drawObjects()
        {
            pAux = selectedPen;
            for (int i = 0; i < objects.Count; i++)
            {
                for(int ed = 0; ed < objects[i].getEdges().Count; ed++)
                {
                    frontGraphics.DrawRectangle(recPen, (objects[i].getEdges()[ed].getPoint1().X + 332), -(objects[i].getEdges()[ed].getPoint1().Y - 170), 2, 2);
                    rightGraphics.DrawRectangle(recPen, objects[i].getEdges()[ed].getPoint1().Z + 332, -(objects[i].getEdges()[ed].getPoint1().Y - 170), 2, 2);
                    topGraphics.DrawRectangle(recPen, objects[i].getEdges()[ed].getPoint1().X + 332, -(objects[i].getEdges()[ed].getPoint1().Z - 170), 2, 2);

                    if (objects[i].getEdges().Count > 0)
                    {
                        if (objects[i].selected == true)
                            pAux = selectedPen;
                        else
                            pAux = linePen;
                        frontGraphics.DrawLine(pAux, objects[i].getEdges()[ed].getPoint1().X + 332, -(objects[i].getEdges()[ed].getPoint1().Y -170), 
                                               objects[i].getEdges()[ed].getPoint2().X + 332, -(objects[i].getEdges()[ed].getPoint2().Y -170));
                        rightGraphics.DrawLine(pAux, objects[i].getEdges()[ed].getPoint1().Z + 332, -(objects[i].getEdges()[ed].getPoint1().Y - 170),
                                                objects[i].getEdges()[ed].getPoint2().Z + 332, -(objects[i].getEdges()[ed].getPoint2().Y - 170));
                        topGraphics.DrawLine(pAux, objects[i].getEdges()[ed].getPoint1().X + 332, -(objects[i].getEdges()[ed].getPoint1().Z - 170),
                                               objects[i].getEdges()[ed].getPoint2().X + 332, -(objects[i].getEdges()[ed].getPoint2().Z - 170));
                        
                    }
                }          
            }
        }


