MonoGame GetData 实现了异常

我刚开始学习XNA/MonoGame，遇到了一个奇怪的异常。
错误说：The method or operation is not implemented.
更奇怪的是，一个非常相似的代码，几乎相同的代码，工作。唯一的区别是其他代码在XNA和另一台计算机上运行，而我的代码在MonoGame上运行。

该代码应该从精灵表制作动画。

在我的课堂上，Animate：

    public void set_state(string name, string state)
    {
        this.name = name;
        this.state = state;
    }
    public void animate(int frameIndex) 
    {
        this.frameIndex = frameIndex;
        this.animatedTexture = Game1.contentManager.Load<Texture2D>(name + '/' + state);
        prepare_frames();
        while (this.frameIndex > rectangles.Count )
        {
            frameIndex = frameIndex - rectangles.Count;
        }
        base.draw(animatedTexture, rectangles[frameIndex], origins[frameIndex]);
    }
    public void prepare_frames()
    {
        find_dots();
        find_rectangles();
        find_origins();
    }
    public void find_dots()
    {
        cols = new Color[animatedTexture.Width];
        lowestRectangle = new Rectangle(0, animatedTexture.Height - 1, animatedTexture.Width, 1);
        animatedTexture.GetData<Color>(0, lowestRectangle, cols, 0, animatedTexture.Width);
        for (int i = 0; i < cols.Length; i++)
        {
            if (cols[i] == Color.Black)
            {
                dots.Add(new Vector2(i, animatedTexture.Height));
            }
        }
    }
    public void find_rectangles()
    {
        for (int i = 0; i < dots.Count-2; i+=2)
        {
            rectangles.Add(new Rectangle((int)dots[i].X, 0, (int)dots[i+2].X - (int)dots[i].X, animatedTexture.Height-1));
        }
    }
    public void find_origins()
    {
        for (int i = 1; i < dots.Count; i++)
        {
            if (i%2 != 0)
            {
                origins.Add(dots[i]);
            }
        }
    }

背后的想法是，在精灵表下面有一排点，我可以用这些点从精灵表上制作框架。以下是类Animated的数据：

    #region data
    Texture2D animatedTexture;
    string name, state; // to determine the animated state.
    Rectangle lowestRectangle; // is the rectangle of the dot's.
    Color[] cols; // this array is for the colors on the dot's rectungle.
    List<Vector2> dots = new List<Vector2>(); // this list is for the dot's coordinates on the dot's rectungle.
    List<Rectangle> rectangles = new List<Rectangle>(); // this list is for the new rectungles, each rectungle is a diffirent frame from the sprite sheet.       
    List<Vector2> origins = new List<Vector2>(); // this list is for each origin point of the new retungles.
    int frameIndex;
    #endregion

以下是在 MonoGame 的主类中召唤上述方法的部分，Game1：

    protected override void Draw(GameTime gameTime)
    {
        GraphicsDevice.Clear(Color.CornflowerBlue);
        spriteBatch.Begin();
        if (Keyboard.GetState().IsKeyDown(Keys.Right))
        {
            player.set_state("moshe", "run");
            player.animate(frameIndex);
            frameIndex++;
        }
        else
            player.draw();
        spriteBatch.End();
        base.Draw(gameTime);
    }

所以错误发生在这一行中：

animatedTexture.GetData<Color>(0, lowestRectangle, cols, 0, animatedTexture.Width); 

在方法中animate类Animate .（ The method or operation is not implemented. ）当我按右键时。为什么会这样？