C# 更改矩形类型列表中的元素值

我正在努力将列表中特定索引处的元素值设置为新值。

该列表的类型是对象矩形，当我尝试更改列表中矩形的任何值时，我收到以下错误，例如

属性或索引器"系统.绘图.矩形.底部"不能 分配给 -- 它是只读的

我尝试将列表转换为数组，但我仍然遇到值为只读的相同问题。

基本上，该应用程序接受用户定义的矩形数量，并沿着相同的基线绘制具有不同宽度和高度的矩形。我尝试实现的代码需要获取这些矩形并从底部向上垂直重绘它们，同时保持与先前创建的矩形相同的矩形数并保持相同的外部形状。

法典：

public void RotateRectangles(List<Rectangle> Rectangles, int startPositionX, int userInput, Graphics DrawingSurface)
    {
        Graphics RectangleGraphics = DrawingSurface;
        try
        {
            // loop in reverse to compare one rectangle to all the other rectangles in the vector
            for (int i = Rectangles.Count - 1; i > -1; --i)
            {
                bool mustChange = true;
                for (int t = Rectangles.Count - 1; t > -1; --t)
                {
                    // only compare if the current position in the vector A if different to the position in vector B.
                    if (i > t)
                    {
                        if (mustChange == true)
                        {
                            // If the top Y coordinate of RECT at Position i in vector A is bigger than Y coordinate
                            // at Position t in vector B
                            if (Rectangles[i].Top >= Rectangles[t].Top)
                            {
                                //adjusting points accordingly
                                Rectangles[i].Left = (Rectangles[t].Left);
                                Rectangles[t].Bottom = (Rectangles[i].Top);
                            }
                            else
                            {
                                // If the Y coordinate is not bigger, then we need to stop checking
                                mustChange = false;
                            }
                        }
                    }
                }
            }
            // loop forward to compare one rectangle to all the other rectangles in the vector
            for (int i = 0; i < Rectangles.Count; ++i)
            {
                bool forwardChange = true;
                for (int t = 0; t < Rectangles.Count; ++t)
                {
                    // If the top Y coordinate of RECT at Position i in vector A is bigger than Y coordinate at Position t
                    // in vector B AND the two rectangales touch
                    if (i < t && Rectangles[i].Top <= Rectangles[t].Bottom)
                    {
                        if (forwardChange == true)
                        {
                            // If the top Y coordinate of RECT at Position i in vector A is bigger than Y coordinate at Position t 
                            // in vector B
                            if (Rectangles[i].Top > Rectangles[t].Top)
                            {
                                //adjusting points accordingly
                                Rectangles[i].Right = (Rectangles[t].Right);
                                Rectangles[t].Bottom = (Rectangles[i].Top);
                            }
                            else
                            {
                                // If the Y coordinate is not bigger, then we need to stop checking
                                forwardChange = false;
                                // Addjust the Y position of each rectangle so it does not overlap with the first drawing
                                for (int z = 0; z < Rectangles.Count; ++z)
                                {
                                    Rectangles[z].Top = (250 - Rectangles[z].Top);
                                    Rectangles[z].Bottom = (250 - Rectangles[z].Bottom);
                                }
                            }
                        }
                    }
                }
            }
            for (int z = 0; z < Rectangles.Count; ++z)
            {
                Rectangle DrawRec = myRectangleClass.MyRectangle(Rectangles[z].Left, Rectangles[z].Top, Rectangles[z].Right, Rectangles[z].Bottom);
                RectangleGraphics.DrawRectangle(Pen, DrawRec);
                ReadWrite.writeOutput(Rectangles[z].Left, Rectangles[z].Top, Rectangles[z].Right, Rectangles[z].Bottom);
            }
        }
        catch (Exception e)
        {
        }
    }

给出错误的部分是：

Rectangles[i].Left = (Rectangles[t].Left);
Rectangles[t].Bottom = (Rectangles[i].Top);
Rectangles[i].Right = (Rectangles[t].Right);
Rectangles[t].Bottom = (Rectangles[i].Top);
Rectangles[z].Top = (250 - Rectangles[z].Top);
Rectangles[z].Bottom = (250 - Rectangles[z].Bottom);

请有人帮助我，或者至少引导我朝着正确的方向前进

Rectangle ri = Rectangles[i];
Rectangle rt = Rectangles[t];
Rectangle[i] = new Rectangle( rt.Left, ri.Bottom, rt.Height, rt.Width );

List<Rectangle> a; 
a[4].X += 4; // does the same like the following code:
var r = a[4] 
r.X += 4; // will change r, but not a[4] 

Rectangles[i] = new Rectangle(Rectangles[t].Left, Rectangles[i].Top, Rectangles[i].Width, Rectangles[i].Height);