为什么我不能使用这段代码？ [英] Why I cannot used this code?

问题描述

 使用 System.Collections.Generic; 
 
 命名空间 ConsoleApplication2 
 {
  class  Program 
 {
 私有 静态  void  Main（ string  [] args）
 {
 Dictionary< int，HandlerBase< TBaseClass，SBaseClass>> dictionary =  new  Dictionary< int，HandlerBase< TBaseClass，SBaseClass>>（）; 
 HandlerBase< TempT，TempS> temp =  new  TempHandler（）; 
 
 dictionary.Add（ 1 ，temp）; 
} 
} 
 
  class  TBaseClass 
 {
 
} 
 
  class  SBaseClass 
 {
 
} 
 
  class  TempT：TBaseClass 
 {
 
} 
 
  class  TempS ：SBaseClass 
 {
 
} 
 
 
  class  HandlerBase< T，S> 
 其中 T：TBaseClass 
 其中 S：SBaseClass 
 {
 
} 
 
  ///   /////// ////////////////////////////// 
  
  class  TempHandler：HandlerBase< TempT，TempS> 
 {
  public  TempHandler（）{} 
} 
 
 
} 

我的尝试：



我'我试图采用通用T基类并在字典中使用它。

解决方案

HandlerBase< tbaseclass，> 与 HandlerBase< tempt，> 不同，甚至 TempT 继承 TBaseClass 和 TempS 继承 SBaseClass ...

你应该定义字典要容纳 HandlerBase< tempt，> ...





为了让你明白更多...

泛型实际上是一种泛型类型，它可以有不同的实际类型，但是当你实际创建一个实例时，那个实例不是通用的再...它有一个非常具体，定义良好的类型，内部继承不属于它（替换 TBaseClass 和 S BaseClass 用对象来更清楚地看到它）...

你所期望的，同一个泛型的不同实例表现得像一个来自另一个的继承对象 - 错误...



参见例如 List< string> 和 List< int> ...如果您遵循逻辑而不是 List< string> 的任何成员可以转换为 List<的成员; int> ，但这意味着，任何字符串都可以转换为 int - 并且我们知道不是真的......

（缺少的线索是int和string都具有相同的基类）

[/ EDIT]

using System.Collections.Generic;

namespace ConsoleApplication2
{
    class Program
    {
        private static void Main(string[] args)
        {
            Dictionary<int, HandlerBase<TBaseClass, SBaseClass>> dictionary = new Dictionary<int, HandlerBase<TBaseClass, SBaseClass>>();
            HandlerBase<TempT, TempS> temp = new TempHandler();

            dictionary.Add(1, temp);
        }
    }

    class TBaseClass
    {

    }

    class SBaseClass
    {

    }

    class TempT : TBaseClass
    {

    }

    class TempS : SBaseClass
    {

    }


    class HandlerBase<T, S>
        where T : TBaseClass
        where S : SBaseClass
    {

    }

    ////////////////////////////////////////

    class TempHandler : HandlerBase<TempT, TempS>
    {
        public TempHandler() { }
    }


}

What I have tried:

I'm trying to take a generic T base class and used it in dictionary.

解决方案

HandlerBase<tbaseclass,> is not the same as HandlerBase<tempt,>, even TempT inherits TBaseClass and TempS inherits SBaseClass...
You should define dictionary to hold HandlerBase<tempt,>...

[EDIT]
To make it clear more for you...
A generic is a actually a generic type, that can have different actual types, but the very moment you actually created an instance, that instance not generic anymore...it has a very specific, well defined type, and inner inheritance not part of it (replace TBaseClass and SBaseClass with object to see it more clearly)...
What you have expected, that the different instances of the same generics behave like inherited object one from the other - wrong...

See for instance List<string> and List<int>...If you follow your logic than any member of List<string> can be converted to a member of List<int>, but that means, that any string can be converted to int - and that we know not to be true...
(The missing clue is that both int and string has the same base class)
[/EDIT]

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