如何尝试解析枚举值? [英] How to TryParse for Enum value?

问题描述

我想编写一个函数，该函数可以根据 enum 的可能值验证给定值(作为字符串传递).在匹配的情况下，它应该返回枚举实例；否则，它应该返回一个默认值.

I want to write a function which can validate a given value (passed as a string) against possible values of an enum. In the case of a match, it should return the enum instance; otherwise, it should return a default value.

函数内部不能使用try/catch，不包括使用Enum.Parse，当给定无效参数时会抛出异常.

The function may not internally use try/catch, which excludes using Enum.Parse, which throws an exception when given an invalid argument.

我想使用类似于 TryParse 函数的内容来实现这一点:

I'd like to use something along the lines of a TryParse function to implement this:

public static TEnum ToEnum<TEnum>(this string strEnumValue, TEnum defaultValue)
{
   object enumValue;
   if (!TryParse (typeof (TEnum), strEnumValue, out enumValue))
   {
       return defaultValue;
   }
   return (TEnum) enumValue;
}

推荐答案

正如其他人所说，您必须实现自己的 TryParse.Simon Mourier 提供了一个完整的实现，可以处理所有事情.

As others have said, you have to implement your own TryParse. Simon Mourier is providing a full implementation which takes care of everything.

如果您使用位域枚举(即标志)，您还必须处理像 "MyEnum.Val1|MyEnum.Val2" 这样的字符串，它是两个枚举值的组合.如果你只是用这个字符串调用 Enum.IsDefined，它会返回 false，即使 Enum.Parse 正确处理它.

If you are using bitfield enums (i.e. flags), you also have to handle a string like "MyEnum.Val1|MyEnum.Val2" which is a combination of two enum values. If you just call Enum.IsDefined with this string, it will return false, even though Enum.Parse handles it correctly.

更新

正如 Lisa 和 Christian 在评论中提到的，Enum.TryParse 现在可用于 .NET4 及更高版本的 C#.

MSDN 文档

As mentioned by Lisa and Christian in the comments, Enum.TryParse is now available for C# in .NET4 and up.

MSDN Docs

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