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我正在努力将列表中特定索引处的元素值设置为新值。

该列表是对象矩形类型，当我尝试更改列表中矩形的任何值时出现以下错误，例如

无法将属性或索引器“System.Drawing.Rectangle.Bottom”分配给 - 它是只读的

我尝试将列表转换为数组，但我仍然遇到相同的值是只读的问题。

基本上，该应用程序接受用户定义数量的矩形并绘制具有不同宽度和高度但沿相同基线的矩形。我试图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，同时保持相同数量的矩形并保持与先前创建的矩形相同的外部形状。

代码：

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);

请有人可以帮助我或至少将我引向正确的方向

4

3 回答 3

2

属性 Right、Left、Top、Bottom 是只读的。您可以使用 Offset 和 Inflate 方法以及 Location、Size、Width 和 Height 属性来调整矩形的位置和大小，或者您可以用新创建的矩形替换现有矩形。

例如

Rectangle ri = Rectangles[i];
Rectangle rt = Rectangles[t];

Rectangle[i] = new Rectangle( rt.Left, ri.Bottom, rt.Height, rt.Width );
于 2012-04-15T11:05:22.913 回答
2

问题不在于矩形的值类型，而在于 List[] 运算符返回一个新的值对象。

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]

所以你需要将矩形值存储在列表中

于 2012-04-15T13:20:43.177 回答
1 
Rectangles[i] = new Rectangle(Rectangles[t].Left, Rectangles[i].Top, Rectangles[i].Width, Rectangles[i].Height);

为所需索引分配一个新矩形。

于 2012-04-15T11:05:24.237 回答