Visual c#在按钮前面绘制图形

我正在做一个winform项目(visual c#)。其中一个表单上有许多按钮，它们彼此相邻。我想在这些按钮前面添加图形，让用户可以一直按按钮。我不能在后面添加图形，因为按钮隐藏了图形，我不想移动按钮。我试着把控制装置搬到后面，但不管用。什么好主意吗?谢谢!

toPolygon.Insert(toPolygon.Count, button); //insert button to vector
System.Drawing.Pen myPen;
myPen = new System.Drawing.Pen(System.Drawing.Color.Black);
myPen.Width = 10;
System.Drawing.Graphics formGraphics = this.CreateGraphics();
formGraphics.DrawLine(myPen, toPolygon[toPolygon.Count - 2].Location.X, toPolygon[toPolygon.Count - 2].Location.Y,
    button.Location.X , button.Location.Y); //draw a line from last button in the vector to the new one
myPen.Dispose();
if (toPolygon.First() == toPolygon.Last())
{   
    //draw polygon and clean the vector
}