C# 显式转换字符串到枚举
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/1061228/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
C# explicit cast string to enum
提问by Boris Gougeon
I would like to have an explicit cast between from a string to an enum in c# in order to have this :
我想在 c# 中从字符串到枚举之间进行显式转换，以便：
(MyEnum) Enum.Parse(typeof(MyEnum),stringValue)
I would like to deport this into an explicit cast operator, I did this but didn't work :
我想将其驱逐到显式转换运算符中，我这样做了但没有用：
public static explicit operator (MyEnum)(value stringValue){
return (MyEnum) Enum.Parse(typeof(MyEnum),stringValue);
}
Do you know if it's possible in C# using .NET 3.5?
您知道在 C# 中使用 .NET 3.5 是否可行吗？
采纳答案by jason
A cast is not possible. The issue is that a user-defined conversion must be enclosed in a struct or class declaration, and the conversion must be to or from the enclosing type. Thus,
无法进行演员表。问题是用户定义的转换必须包含在结构或类声明中，并且转换必须是与封闭类型之间的转换。因此，
public static explicit operator MyEnum(string value)
is impossible because neither MyEnumnor stringcan ever be the enclosing type.
是不可能的，因为既不能MyEnum也string不能是封闭类型。
The relevant section of the ECMA334 C# spec is 17.9.4:
ECMA334 C# 规范的相关部分是 17.9.4：
A conversion operator converts from a source type, indicated by the parameter type of the conversion operator, to a target type, indicated by the return type of the conversion operator. A class or struct is permitted to declare a conversion from a source type S to a target type T only if all of the following are true, where S0 and T0 are the types that result from removing the trailing ? modifiers, if any, from S and T:
转换运算符将源类型（由转换运算符的参数类型指示）转换为目标类型（由转换运算符的返回类型指示）。仅当以下所有条件都为真时，才允许类或结构声明从源类型 S 到目标类型 T 的转换，其中 S0 和 T0 是删除尾随的 ? 来自 S 和 T 的修饰符，如果有的话：
S0 and T0 are different types.
S0 和 T0 是不同的类型。
Either S0 or T0 is the class or struct type in which the operator declaration takes place.
S0 或 T0 是发生运算符声明的类或结构类型。
Neither S0 nor T0 is an interface-type.
S0 和 T0 都不是接口类型。
Excluding user-defined conversions, a conversion does not exist from S to T or from T to S.
排除用户定义的转换，不存在从 S 到 T 或从 T 到 S 的转换。
However, you can do an extension method on the string class.
但是，您可以对字符串类执行扩展方法。
public static class StringExtensions {
public static T ConvertToEnum<T>(this string value) {
Contract.Requires(typeof(T).IsEnum);
Contract.Requires(value != null);
Contract.Requires(Enum.IsDefined(typeof(T), value));
return (T)Enum.Parse(typeof(T), value);
}
}
回答by Andy
Is it necessary to use a cast operator? Another option would be to add an extension method off of string:
是否有必要使用强制转换运算符？另一种选择是从字符串中添加一个扩展方法：
public static class StringEnumConversion
{
public static T Convert<T>(this string str)
{
return (T)Enum.Parse(typeof(T), str);
}
}
回答by andy
You could also use "StringValue" attributes for get what you want.
您还可以使用“StringValue”属性来获取您想要的内容。
Check out this question: stackoverflow.com/questions/424366/c-string-enums, there's plenty of info there that might help.
看看这个问题：stackoverflow.com/questions/424366/c-string-enums，那里有很多可能有帮助的信息。
cheers
干杯
