将附加信息与.NET枚举相关联 [英] Associating Additional Information with .NET Enum

问题描述

假设我有枚举：

  public enum ArrowDirection 
 {
北，
南，
东，
西
} 
  

我想将与每个方向相对应的单位向量与该方向相关联。例如，我想要的东西将返回（0，1）为North，（-1，0）为西等。我知道在Java中，你可以声明一个方法在枚举内可以提供这个功能。

我目前的解决方案是在定义枚举的类中有一个静态方法 - 返回与ArrowDirection中传递的向量相对应的向量（该方法使用HashTable来完成查找但这并不重要）。这个似乎是不洁净的。

问题：

是否有一个最佳实践解决方案来存储对应于枚举的附加信息.NET？

解决方案

在C＃3.0中有一种FANTASTIC新方法。关键是这个美丽的事实：枚举可以有扩展方法！所以，你可以这样做：

  public enum ArrowDirection 
 {
 North，
南，
东，
西
} 
 
 public static class ArrowDirectionExtensions 
 {
 public static UnitVector UnitVector（this ArrowDirection self）
 {
 //将此替换为字典或任何你想要的...你得到的想法
 switch（self）
 {
 case ArrowDirection.North：
返回新UnitVector（0，1）; 
 case ArrowDirection.South：
 return new UnitVector（0，-1）; 
 case ArrowDirection.East：
 return new UnitVector（1，0）; 
 case ArrowDirection.West：
 return new UnitVector（-1，0）; 
默认值：
返回null; 
} 
} 
} 
  

现在，你可以这样做：

  var unitVector = ArrowDirection.North.UnitVector（）; 
  

甜蜜！大约一个月前我才发现这一点，但这是新的C＃3.0功能的一个非常好的结果。

这是我博客上的另一个例子

My question is best illustrated with an example.

Suppose I have the enum:

public enum ArrowDirection
{
    North,
    South,
    East,
    West
}

I want to associate the unit vector corresponding to each direction with that direction. For example I want something that will return (0, 1) for North, (-1, 0) for West, etc. I know in Java you could declare a method inside the enum which could provide that functionality.

My current solution is to have a static method -- inside the class that defines the enum -- that returns a vector corresponding to the passed in ArrowDirection (the method uses a HashTable to accomplish the lookup but that's not really important). This seems... unclean.

Question:
Is there a best-practice solution for storing additional information corresponding to an enum in .NET?

解决方案

There's a FANTASTIC new way to do this in C# 3.0. The key is this beautiful fact: Enums can have extension methods! So, here's what you can do:

public enum ArrowDirection
{
    North,
    South,
    East,
    West
}

public static class ArrowDirectionExtensions
{
     public static UnitVector UnitVector(this ArrowDirection self)
     {
         // Replace this with a dictionary or whatever you want ... you get the idea
         switch(self)
         {
             case ArrowDirection.North:
                 return new UnitVector(0, 1);
             case ArrowDirection.South:
                 return new UnitVector(0, -1);
             case ArrowDirection.East:
                 return new UnitVector(1, 0);
             case ArrowDirection.West:
                 return new UnitVector(-1, 0);
             default:
                 return null;
         }
     }
}

Now, you can do this:

var unitVector = ArrowDirection.North.UnitVector();

Sweet! I only found this out about a month ago, but it is a very nice consequence of the new C# 3.0 features.

Here's another example on my blog.

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