为什么不能在.NET中定义泛型索引器？

问题描述

为什么不能在.NET中创建通用索引器？

以下代码会引发编译器错误：

  public T this< T> [string key] 
 {
 get {/ *返回泛型类型T. * /} 
} 
  

这是否意味着您无法为通用成员集合创建通用索引器？

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解决方案

我能想到的唯一可以使用的就是这些行： pre> var settings = ConfigurationSection.AppSettings;
var connectionString = settings< string> [connectionString];
var timeout = settings< int> [timeout];


但是这实际上并不会为您购买任何东西。你刚刚用尖括号替换了圆括号（如在（int）设置[timeout]中），但没有获得额外的类型安全，因为你可以自由地做到这一点

  var timeout = settings< int> [connectionString]; 
  

如果您有强烈但未静态类型的东西，您可能要等到C＃4.0 动态关键字。

Why can't you create a generic indexer in .NET?

the following code throws a compiler error:

   public T this<T>[string key]
   {
      get { /* Return generic type T. */ }
   }

Does this mean you can't create a generic indexer for a generic member collection?

解决方案

The only thing I can think of this can be used is something along these lines:

var settings = ConfigurationSection.AppSettings;
var connectionString = settings<string>["connectionString"];
var timeout = settings<int>["timeout"];

But this doesn't actually buy you anything. You've just replaced round parens (as in (int)settings["timeout"]) with angle brackets, but received no additional type safety as you can freely do

var timeout = settings<int>["connectionString"];

If you have something that's strongly but not statically typed, you might want to wait until C# 4.0 with its dynamic keyword.

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