可派生類隱藏訪問器 - 以下代碼有什麼問題

Question

我想隱藏派生類中的訪問器，它有效嗎？我的系統在執行時沒有迴應。

class BaseCS 
    { 
     private string name; 

     public string Name 
     { 
      get { return name; } 
      set { name = "Base " + value; } 
     }  
    } 

    class DerivedCS : BaseCS 
    { 
     public new string Name 
     { 
      set { Name = "Der " + value; } 
      get { return Name; } 
     } 
    } 

public static void Main() 
     { 
      BaseCS one = new DerivedCS(); 

      one.Name = "One"; 

      Console.WriteLine("Name of object one is {0} ", one.Name); 


      ((BaseCS)one).Name = "On1"; 
      Console.WriteLine("Name of object one is {0} ", one.Name); 
     } 

不應該我期望輸出爲，

Name of object one is Base Der One 
Name of object one is Base On1 

Answer 1

1. 此代碼：

   public new string Name 
   { 
       set { Name = "Der " + value; } 
       get { return Name; } 
   } 
   

   會導致堆棧溢出，因爲在getter和setter方法將參照Name到DerivedCS中的Name，而不是BaseCS。 Name財產將永遠自稱，直到崩潰。您需要使用base.Name。

2. 你可能想要的是polymorphysm。您應該在派生類中創建屬性virtual和override setter。

   如果你不使用的虛擬特性，以下對象將不會表現你所希望的方式：

   BaseCS one = new DerivedCS(); 
   one.Name = "name"; // base implementation is called 
   

3. 在二傳手更改屬性值通常是一個壞主意。用戶期望要遵循以下合約：

   var a = new A(); 
   a.Foo = "bar"; 
   Debig.Assert(a.Foo == "bar"); 
   

Answer 2

這裏是你應該做的事情

class BaseCS 
    { 
     private string name; 

     public virtual string Name 
     { 
      get { return name; } 
      set { name = "Base " + value; } 
     } 

    } 

    class DerivedCS : BaseCS 
    { 
     public override string Name 
     { 
      set { base.Name = "Der " + value; } 
      get { return base.Name; } 
     } 
    } 

，或者用新的關鍵字

class BaseCS 
    { 
     private string name; 

     public string Name 
     { 
      get { return name; } 
     set { name = "Base " + value; } 
    } 

} 

class DerivedCS : BaseCS 
{ 
    public new string Name 
    { 
     set { base.Name = "Der " + value; } 
     get { return base.Name; } 
    } 
} 

now you should create the object as the derived type to get your expected result 

    DerivedCS one = new DerivedCS();