我怎样才能在WPF绘制

我需要在图像绘制一些图形元素（椭圆形，矩形等）。我写了下面的代码:

 protected GeometryDrawing PaintEllipse(Int32 Left, Int32 Top, Int32 Width, Int32 Height, Pen Pen)

        {

            GeometryDrawing returnedValue = null;

 

            EllipseGeometry ellipseGeometry = new EllipseGeometry(new Rect(Left, Top, Width, Height));

 

            returnedValue=new GeometryDrawing(null, Pen, ellipseGeometry);

 

            return returnedValue;

        }

 

        protected GeometryDrawing PaintRectangle(Int32 Left, Int32 Top, Int32 Width, Int32 Height, Pen Pen)

        {

            GeometryDrawing returnedValue = null;

 

            RectangleGeometry rectangleGeometry=new RectangleGeometry(new Rect(Left, Top, Width, Height));

 

            returnedValue=new GeometryDrawing(null, Pen, rectangleGeometry);

 

            return returnedValue;

        }

 

       

        void Drawing(String[] Elements, Image MyImage)

    {

    foreach(String currentElement in Elements)

    {

    switch(currentElement)

    {

    case("PaintEllipse"):

    {

    MyImage.Source+=PaintEllipse(0,0,40,70,new Pen(Brushes.Black, 3));

    break;

    }

    case("PaintRectangle"):

    {

    MyImage.Source+=PaintRectangle(0,0,40,70,new Pen(Brushes.Black, 3));

    break;

    }

    //etc.

    }

    }

    }