如何創建新對象並更改其他引用

Question

如何在不丟失Y上的X引用的情況下做到這一點？

 public class Test 
     { 
      public void Main() 
      { 
       AbstractClass X = new Foo(); 

       Test2 test2 = new Test2(X); 

       X = new Bar(); // I need to change Y as well. 

       //Now, X is Bar, and Y is Foo. 
       if (X == test2.Y) 
        MessageBox.Show("They are equal! Success!!"); 
       else 
        MessageBox.Show("Not equal :("); 
      } 
     } 

     public class Test2 
     { 
      public AbstractClass Y { get; set; } 

      public Test2(AbstractClass y) 
      { 
       Y = y; 
      } 
     } 

     public abstract class AbstractClass 
     { } 

     public class Foo : AbstractClass 
     { } 

     public class Bar : AbstractClass 
     { } 

Answer 1

你不能。如果你需要這樣的東西，你可以將AbstractClass包裝在另一箇中，並將其作爲參考。

這裏是你如何去：

public class MyPropertyStore 
{ 
    public AbstractClass MyProperty {get;set;} 
} 

public class Test2 
{  
    private MyPropertyStore propertyStore; 
    public AbstractClass Y { get { return propertyStore.MyProperty ;} } 

    public Test2(MyPropertyStore propertyStore) 
    { 
     this.propertyStore= propertyStore; 
    } 
} 

public void Main() 
{ 
    AbstractClass X = new Foo(); 
    MyPropertyStore store = new MyPropertyStore 
    { 
    MyProperty = X, 
    }; 
    Test2 test2 = new Test2(store); 

    store.MyProperty = new Bar(); // Now test2.Y will be pointing to same reference 

    //Now, X is Bar, and Y is Foo. 
    if (X == test2.Y) 
     MessageBox.Show("They are equal! Success!!"); 
    else 
     MessageBox.Show("Not equal :("); 
} 

Answer 2

我不知道你試圖實現什麼，但我想你想的fowllowing發生：

public void Main() 
{ 
    AbstractClass X = new Foo(); 

    Test2 test2 = new Test2(X); 

    X = new Bar(); 

    // change test2.Y 
    test2.Y = X; 

    if (X == test2.Y) 
     MessageBox.Show("They are equal! Success!!"); 
    else 
     MessageBox.Show("Not equal :("); 
}