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POc# - reference type referencing another reference type
 

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    <p>Note: This applies to both List and ArrayList</p> <p>Take a look at the following simple code:</p> <pre><code>class Creature { public string Name; } class Game { // This is a reference type public Creature CurrentCreature; } class Program { static void Main(string[] args) { // First, we'll create 2 objects and let the // reference type "CurrentCreature" points to one of them Creature dragon = new Creature(); dragon.Name = "Dragon"; Creature Unicorn = new Creature(); dragon.Name = "Unicorn"; Game game = new Game(); game.CurrentCreature = dragon; // Now we'll create a list which will contain // the reference type "CurrentCreature" List&lt;Creature&gt; list = new List&lt;Creature&gt;(); list.Add(game.CurrentCreature); foreach (Creature c in list) { Console.WriteLine(c.Name); // Output is "Dragon" } // Now, we'll let "CurrentCreature" point to a different object game.CurrentCreature = unicorn; // The reference in the list still pointing to the original object!!! foreach (Creature c in list) { Console.WriteLine(c.Name); // Output is "Dragon"!!! } Console.ReadLine(); } } </code></pre> <p>I checked how a list adds an item and there is no instantiation of a new object. This is List.Add method (using Reflector tool)</p> <pre><code> public void Add(T item) { if (this._size == this._items.Length) { this.EnsureCapacity(this._size + 1); } this._items[this._size++] = item; // No instantiation this._version++; } </code></pre> <p>So, why is this happenning? The element in the list should be a reference to the object pointed to by "CurrentCreature" or is it not? Isn't it similar to the following code if we remove the list?:</p> <pre><code>class A { public B X; } class B { public string Name; } .... A a = new A(); B b1 = new B(); b1.Name = "b1"; B b2 = new B(); b2.Name = "b2"; a.X = b1; Console.WriteLine(a.X.Name); // output: b1 b1 = b2; Console.WriteLine(a.X.Name); // output: b1 </code></pre>
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    1. USSaleh Al-Abbas
    1. USSaleh Al-Abbas
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    1. COThe last example, I included with A & B classes, shows that I'm mixing things up. The question is not related to list and Array list but to Reference types in general.
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      1. POc# - reference type referencing another reference type
      1. USSaleh Al-Abbas
 

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