Parse string to enum type

问题:

I have an enum type like this as an example:

public Enum MyEnum {     enum1, enum2, enum3 }; 

I'll read a string from config file. What I need it to parse the string to MyEnum type or null o not defined. Not sure if the following codes will work (sorry for not having access to my VS right now):

// example: ParseEnum<MyEnum>("ENUM1", ref eVal); bool ParseEnum<T>(string value1, ref eVal) where T : Enum {   bool bRet = false;   var x = from x in Enum.GetNames(typeof(T)) where         string.Equals(value1, x, StringComparison. OrdinalIgnoreCase)        select x;   if (x.Count() == 1 )   {     eVal = Enum.Parse(typeof(T), x.Item(0)) as T;     bRet = true;   }   return bRet; } 

Not sure if it is correct or there is any other simple way to parse a string to MyEnum value?

回答1:

What about something like:

public static class EnumUtils {     public static Nullable<T> Parse<T>(string input) where T : struct     {         //since we cant do a generic type constraint         if (!typeof(T).IsEnum)         {             throw new ArgumentException("Generic Type 'T' must be an Enum");         }         if (!string.IsNullOrEmpty(input))         {             if (Enum.GetNames(typeof(T)).Any(                   e => e.Trim().ToUpperInvariant() == input.Trim().ToUpperInvariant()))             {                 return (T)Enum.Parse(typeof(T), input, true);             }         }         return null;     } } 

Used as:

MyEnum? value = EnumUtils.Parse<MyEnum>("foo"); 

(Note: old version used try/catch around Enum.Parse)

回答2:

private enum MyEnum {     Enum1 = 1, Enum2 = 2, Enum3 = 3, Enum4 = 4, Enum5 = 5, Enum6 = 6,      Enum7 = 7, Enum8 = 8, Enum9 = 9, Enum10 = 10 }  private static Object ParseEnum<T>(string s) {     try     {         var o = Enum.Parse(typeof (T), s);         return (T)o;     }     catch(ArgumentException)     {         return null;     } }  static void Main(string[] args) {    Console.WriteLine(ParseEnum<MyEnum>("Enum11"));    Console.WriteLine(ParseEnum<MyEnum>("Enum1"));    Console.WriteLine(ParseEnum<MyEnum>("Enum6").GetType());    Console.WriteLine(ParseEnum<MyEnum>("Enum10")); } 

OUTPUT:

    //This line is empty as Enum11 is not there and function returns a null Enum1 TestApp.Program+MyEnum Enum10 Press any key to continue . . . 

回答3:

This is an old question, but now .NET 4.5 has Enum.TryParse().

http://msdn.microsoft.com/en-us/library/dd991317.aspx

回答4:

I have a TryParseName method in UnconstrainedMelody, a library for delegate and enum utility methods which uses "inexpressible" constraints via some postbuild trickery. (Code using the library doesn't need a postbuild, just to be clear.)

You would use it like this:

Foo foo; bool parsed = Enums.TryParseName<Foo>(name, out foo); 

I don't currently have a case-insensitive version, but I could easily introduce one if you wanted. Note that this doesn't try to parse numbers e.g. "12" like the built-in version does, nor does it try to parse comma-separated lists of flags. I may add the flags version later on, but I can't see much point in the numeric version.

This is done without boxing and without execution time type checking. Having the constraint is really handy :)

Please let me know if you'd find a case-insensitive parse useful...

回答5:

If you're using .NET 3.5 (or even 2.0, if you trim out the extension method), I've had great luck with the techniques in this article:

Enumerations and Strings - Stop the Madness!

EDIT: Domain is gone and is now a link farm. I pulled the code (slightly modified and added to over time) from our codebase at work, which you can now find here:

https://gist.github.com/1305566

回答6:

I have just combined the syntax from here, with the exception handling from here, to create this:

public static class Enum<T> {     public static T Parse(string value)     {         //Null check         if(value == null) throw new ArgumentNullException("value");         //Empty string check         value = value.Trim();         if(value.Length == 0) throw new ArgumentException("Must specify valid information for parsing in the string", "value");         //Not enum check         Type t = typeof(T);         if(!t.IsEnum) throw new ArgumentException("Type provided must be an Enum", "TEnum");          return (T)Enum.Parse(typeof(T), value);     } } 

You could twiddle it a bit to return null instead of throwing exceptions.

回答7:

You can use TryParse if you want to avoid using try/catch.

MyEnum eVal; if (Enum.TryParse("ENUM2", true, out eVal)){     // now eVal is the enumeration element: enum2  } //unable to parse. You can log the error, exit, redirect, etc... 

I modified the selected answer a little bit. I hope you like it.

public static class EnumUtils {     public static Nullable<T> Parse<T>(string input) where T : struct     {         //since we cant do a generic type constraint         if (!typeof(T).IsEnum)         {             throw new ArgumentException("Generic Type 'T' must be an Enum");         }          int intVal;         if (!string.IsNullOrEmpty(input) && !int.TryParse(input, out intVal))         {             T eVal;             if (Enum.TryParse(input, true, out eVal))             {                 return eVal;             }         }         return null;     } } 

回答8:

To return Enum by string, if contains:

    public static T GetEnum<T>(string s)     {         Array arr = Enum.GetValues(typeof(T));         foreach (var x in arr)         {             if (x.ToString().Contains(s))                 return (T)x;         }         return default(T);     } 

文章来源: Parse string to enum type