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c#parsingenumscastingtostring
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Reputation: 43

How Can I Successfully Cast a Multi-Valued Enum?

Problem: I can return the string representation of a single valued enum with enum.ToString(). In the cases of multi-valued enum (e.g.: signified using the OR operator |), all I get back in the enum.ToString() call is the integer value because the enum fails to parse.

Work-arounds/Hindrances: I can't create multiple instances of the same value in enum, such as:

public enum Languages: int
{
     English = 0, // From American English
     English = 1, // From UK English
     Spanish = 2, // From Castillian Spanish
     Spanish = 3, // From Latin American Spanish
     Portuguese = 4 // From Brasilian Portuguese
     Portuguese = 5, // From European Portuguese
}

as this violates the standard and the IDE gets super frowny-face about that.

Example of Problem:

public enum Languages: int
{
     English = 0 | 1,   // American or UK
     Spanish = 2 | 3,   // Castillian or Latin American
     Portuguese = 4 | 5,   // Brasil or Portugal
     MyMadeUpLanguage = 6,     
}

int selectedLanguage = 1;
Languages result = (Languages)Enum.Parse(typeof(Languages), selectedLanguage);
string resultString = result.ToString();  // This is where '1' is returned and not English.

int nextSelectedLanguage = 6;
Languages differentResult = (Languages)Enum.Parse(typeof(Languages), nextSelectedLanguage);
string nextResultString = differentResult.ToString();  // This returns 'MyMadeUpLanguage', as we would expect.

Expectations (or what I'm trying to do):

What I'm expecting is that the conditional should match, so 0 or 1 would match English and my enum result would then be Languages.English and, so, the string returned would English and not 1.

Instead, what seems to happen is that the call to parse the enum just returns as an int and not a Language type (referencing the example above), so - of course - the enum.ToString() method returns an int.

For multi-valued enum, where it's possibe that 2 to x <= int.MaxValue values will suffice for the enum, how can I get the call to parse the enum to cast successfully to the expected enum (which would, resultantly, bring the proper string back in the return of the enum.ToString() method)?

Upvotes: 0

Views: 164

Answers (1)

Dmitrii Bychenko
Dmitrii Bychenko

Reputation: 186698

I suggest using Flags attribute, e.g.:

[Flags]
public enum Languages: int
{
     None = 0,                      // None 

     English    = 1 << 30,          // Languages  
     Spanish    = 1 << 29,  
     Portuguese = 1 << 28,   
     MyMadeUpLanguage = 1 << 27, 

                                    // Dialects
     EnglishUS = English | 1,       // From American English
     EnglishGB = English | 2,       // From UK English
     EnglishCA = English | 3,       // From Canada English
     SpanishES = Spanish | 1,       // From Castillian Spanish
     SpanishLA = Spanish | 2,       // From Latin American Spanish
     PortugueseBR = Portuguese | 1, // From Brasilian Portuguese
     PortuguesePT = Portuguese | 2, // From European Portuguese 

     MyMadeUpLanguageDialect1 = MyMadeUpLanguage | 1
}

Typical comparisons:

Languages selectedLanguage ...

if (Languages.EnglishGB & Languages ==  Languages.EnglishGB) {
  // From Exactly English Great Britain
  ...
}

if (Languages.English & Languages == Languages.English) {
  // From some kind of English (Great Britain, or US dialect)
  ...
}

Upvotes: 1

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