关于字典的问题 [英] A question about dictionaries of Dictionaries

问题描述

这是我想做的事情:

here is what I would like to do:

Dictionary<string,Dictionary<string, XxXxXx>> BoB;

其中 XxXxXx 可以是A类，B类，C类...等
和{A，B，C}:Class Z

这样我就可以声明(大致为伪)

where XxXxXx can be class A, class B, class C...etc
and {A,B,C}:Class Z

so that i can declare (roughly-Pseudo)

class Rusty
{

     private Dictionary<String,A> _a;
     private Dictionary<String,B> _b;
     private Dictionary<String,C> _c;

     public Dictionary<String,????> Lookup( identifier id)
     {
          switch(id)
          {
               case id.a: return _a;
               case id.b: return _b;
               case id.c: return _c;}
          }
     }
}

但我能得到的最接近的结果是:
CS1502，CS0029，CS0039 X |

无法通过参考转换，装箱转换，拆箱转换，换行转换将类型"System.Collections.Generic.Dictionary< string，ClassA>"转换为"System.Collections.Generic.Dictionary< string，ClassZ>".或null类型转换

..基本上说我无法完成以上任务..

找不到这种类型的问题"的体面引用:confused:

有什么想法吗?


根据aspdevdotnet的建议(谢谢)

yet the closest I can get results in:
CS1502, CS0029, CS0039 X|

Cannot convert type ''System.Collections.Generic.Dictionary<string,ClassA>'' to ''System.Collections.Generic.Dictionary<string,ClassZ>'' via a reference conversion, boxing conversion, unboxing conversion, wrapping conversion, or null type conversion

..basically says that what i have above can''t be done..

couldn''t find a decent reference for this type of "issue":confused:

any ideas?


As per aspdevdotnet''s suggestion(thank you)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Jumba
{
    class A:Z
    {
    }
    class B:Z
    {
    }
    class C:Z
    {
    }
    class Z
    {
    }
    class Y 
    {
        Dictionary<string, Dictionary<string,Z>> Bob = new Dictionary<string,Dictionary<string,Z>>();
        Dictionary<string, A> _a = new Dictionary<string,A>();
        Dictionary<string, B> _b = new Dictionary<string,B>();
        Dictionary<string, C> _c = new Dictionary<string,C>();
        public Y() 
        {
            //Error	4	Argument ''2'': cannot convert from ''System.Collections.Generic.Dictionary<string,Jumba.A>'' to ''System.Collections.Generic.Dictionary<string,Jumba.Z>''	
            Bob.Add("a",_a);
            //Error	6	Argument ''2'': cannot convert from ''System.Collections.Generic.Dictionary<string,Jumba.A>'' to ''System.Collections.Generic.Dictionary<string,Jumba.Z>''	
            Bob.Add("b",_b);
            //Error	8	Argument ''2'': cannot convert from ''System.Collections.Generic.Dictionary<string,Jumba.A>'' to ''System.Collections.Generic.Dictionary<string,Jumba.Z>''	
            Bob.Add("c",_c);
        }
        public Dictionary<string, Z> Retrieve(string str) 
        {
            Object alpha = Bob[str];
            //Error	15	Cannot implicitly convert type ''Jumba.A'' to ''System.Collections.Generic.Dictionary<string,Jumba.Z>''	
            if (alpha is A){return (alpha as A)}
        
        }
    }

}

推荐答案

关于您的更新样本.您似乎错过了重点.这就是您想要的:

Regarding your updated sample. You seem to have missed the point. This is what you want:

//  Your dictionaries will be of value Z (so, A, B, and C instances can be placed in it).
Dictionary<string, Z> _a = new Dictionary<string,Z>();
Dictionary<string, Z> _b = new Dictionary<string,Z>();
Dictionary<string, Z> _c = new Dictionary<string,Z>();

// Your retrieve method will return a dictionary, not a Z derived instance.
public Dictionary<string, Z> Retrieve(string str)
{
    return Bob[str];
}

或者，如果您想为此类的用户完成工作，则可以有3个Retrieve方法:

Or, you could have 3 Retrieve methods if you want to do the work for the user of this class:

public A RetrieveA(string str) { return Bob["a"][str] as A; }
public B RetrieveB(string str) { return Bob["b"][str] as B; }
public C RetrieveC(string str) { return Bob["c"][str] as C; }

由于C#是强类型的，因此您的类型存在冲突.您可以做的是让A，B和C类从som公共父类(例如AlphaClass)派生，然后创建该类型的字典.或者，由于所有类都是从Object类派生的，因此您可以只使用Object而不是AlphaClass:

Since C# is strongly typed, your types are clashing. What you can do is have classes A, B, and C derive from som common parent class (say, AlphaClass), then create a dictionary of that type. Or, since all classes derive from the Object class, you could just use Object instead of AlphaClass:

// A, B, and C should derive from AlphaClass.
Dictionary<string, Dictionary<string, AlphaClass>> BoB;
// Or, just use Object, since they already derive from that class.
Dictionary<string, Dictionary<string, Object>> BoB;

当您从字典中获得一项时，就可以检查其类型并将其转换为该类型:

When you get one of the items from the dictionary, you can then just check its type and convert it to that type:

Object alpha = BoB["A"]["someKey"];
if(alpha is A) (alpha as A).SomeAMethod();

这正是.Net中接口的作用
使一个接口代表所有类之间的共同点Ex

This exactly what the interfaces do in .Net
Make an interface represent the common stuff between all the classes Ex

public interface IInterface
       {
           int number{get; set;}
           void doSomething();
       }

然后在每个类中实现此接口

Then implement this interface in each class

public classA : IInterface
{
//implementation goes here 
}

和调用步骤(如果只想检索对象)

And the calling step (if you want to retrieve the object only)

public IInterface Retrieve(string str)
      {
          return Bob[str];
      }

或者，如果您想取消字典

Or of if you want to retireve the dictionary

public Dictionary<string,IInterface  > Retrieve(string str)
      {
          return new Dictionary<string, IInterface>().Add(f, Bob[str]);
      }

或使用更好的解决方案，使用Linq(我最喜欢的一种)

Or for better solution use Linq (my favourite one )

public Dictionary<string,IInterface> Retrieve(string str) 
        {
 return Bob.Where(c => c.Key == str ).ToDictionary(c => c.Key, c => c.Value);
}

希望我能帮忙

hope i could help

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