wpf 动态替换path做的图标path.data不懂怎么实现后台赋值

如何在wpf中动态替换一个path做的图标，基本都是前台写的，后台知道是geomerty类型但不懂如何赋值data

给个方法你看看：

///
/// 画间隔线
///
///
private Path AddBackLine()
{
#region
GeometryGroup group = new GeometryGroup();
double circleRate = this.CircleRate;
EllipseGeometry ellipse1 = new EllipseGeometry();
ellipse1.Center = this.CircleCenter;
ellipse1.RadiusX = circleRate;
ellipse1.RadiusY = circleRate;

        circleRate = circleRate - BackLineSpace;

        EllipseGeometry ellipse2 = new EllipseGeometry();
        ellipse2.Center = this.CircleCenter;
        ellipse2.RadiusX = circleRate;
        ellipse2.RadiusY = circleRate;

        circleRate = circleRate - BackLineSpace * 2 - this.OuterButtonArcHighness - BackLineSpace * 2;

        EllipseGeometry ellipse3 = new EllipseGeometry();
        ellipse3.Center = this.CircleCenter;
        ellipse3.RadiusX = circleRate;
        ellipse3.RadiusY = circleRate;

        //group.Children.Add(ellipse1);
        group.Children.Add(ellipse2);
        //group.Children.Add(ellipse3);    

        Path path = new Path();

        path.Data = group;
        path.Fill = null;
        path.Stroke = Brushes.Black;

        return path;
        #endregion
    }