XNA 游戏状态管理引用分配

最近我开始使用游戏状态管理（详细信息：create.msdn.com/en-US/education/catalog/sample/game_state_management），这是XNA制作的简单游戏的绝佳模板。

几天来我一直在分析它的实现，我对 LoadScreen .cs 在这种方法中表示怀疑：

/// <summary>
/// The constructor is private: loading screens should
/// be activated via the static Load method instead.
/// </summary>
private LoadingScreen(ScreenManager screenManager, bool loadingIsSlow,
                      GameScreen[] screensToLoad)
{
    this.loadingIsSlow = loadingIsSlow;
    this.screensToLoad = screensToLoad;
    TransitionOnTime = TimeSpan.FromSeconds(0.5);
}

我不明白为什么会有引用分配：this.screensToLoad = screensToLoad;.为什么不使用类似.Clone()方法？


[编辑]

还行。。。我认为我的问题不是 XNA 或游戏状态管理，我准备了一段代码，解释了我的疑问。

代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace test
{
    public class a
    {
        public int number = 3;
    }
    public class b
    {
        public a tmp;
        public void f(a arg)
        {
            tmp = arg; // (*?*) isn't it dangerous assigning?
        } 
    }
    class Program
    {
        static void Main(string[] args)
        {
            b temp_b = new b();
            {// (*!*) CODE BLOCK COMES HERE:
                a temp_a = new a();
                temp_b.f(temp_a);
                temp_a.number = 4;
            }
            // TROUBLE EXPLANATION:
            // We are outside of code block which I marked with (*!*)
            // Now reference 'temp_a' is inaccessible. 
            // That's why line of code which I marked with (*?*) is dangerous.
            // We saved 'temp_a' which is no longer accessible in 'temp_b' object.
            // 
            // Now computer's memory pointed by reference, which is saved in 'temp_b.tmp' (and was saved in 'temp_a'),
            // can be overriden by code which comes somewhere below this comment (or even in another thread or process).
            //
            // I think the same situation is in XNA GSM's piece of code.
            // The only solution in my opinion is deep copy (AFAIK .Clone() can be implemented as shallow or deep copy).
            Console.WriteLine(temp_b.tmp.number); // result is 4
                                                  // because we copied reference
                                                  // For me it's strange that this line was printed. As I mentioned above
                                                  // memory intended for 'temp_a' could be reused and overwritten.
        }
    }
}

为方便起见，此处相同的代码：ideone.com/is4S3。

我在上面的代码中提出了问题和疑问（请参阅注释）。

public static void Load(ScreenManager screenManager, bool loadingIsSlow,
                        PlayerIndex? controllingPlayer,
                        params GameScreen[] screensToLoad)

LoadingScreen.Load(manager, false, null, s1, s2, s3, s4, s5);