C＃參考變量使用澄清

Question

作爲不是一個程序員，我想明白下面的代碼：

A a=new A(); 
B a=new B(); 

a=b;  
c=null; 

b=c; 

如果這些變量都抱着僅供參考，將「A」進行到底空？

Answer 1

您需要離婚在你的心中兩個概念; 參考和對象。 參考本質上是託管堆上的對象的地址。所以：

A a = new A(); // new object A created, reference a assigned that address 
B b = new B(); // new object B created, reference b assigned that address 
a = b; // we'll assume that is legal; the value of "b", i.e. the address of B 
     // from the previous step, is assigned to a 
c = null; // c is now a null reference 
b = c; // b is now a null reference 

這不會影響「a」或「A」。 「a」仍然包含我們創建的B的地址。

所以不，「a」最後不是零。

Answer 2

假設所有對象a，b，c來自同一類，a將不會是null。在分配到c之前，它將保留參考值b的值。

假設您有以下類

class Test 
{ 
    public int Value { get; set; } 
} 

然後嘗試：

Test a = new Test(); 
a.Value = 10; 
Test b = new Test(); 
b.Value = 20; 
Console.WriteLine("Value of a before assignment: " + a.Value); 
a = b; 
Console.WriteLine("Value of a after assignment: " + a.Value); 
Test c = null; 
b = c; 
Console.WriteLine("Value of a after doing (b = c) :" + a.Value); 

輸出將是：

Value of a before assignment: 10 
Value of a after assignment: 20 
Value of a after doing (b = c) :20