Associating enums with strings in C

Question

I know the following is not possible because the Enumeration s type has to be an int  enum GroupTypes       TheGroup    OEM       TheOtherGroup    CMB      From my database I get a field with incomprehensive codes  the OEM and CMBs   I would want to make this field into an enum or something else understandable  Because if the target is readability  the solution should be terse   What other options do I have

User · Answer

How about using a static class with constants   static class GroupTypes     public const string TheGroup    OEM     public const string TheOtherGroup    CMB      void DoSomething string groupType      if groupType    GroupTypes TheGroup             Be nice         else if  groupType    GroupTypes TheOtherGroup             Continue to be nice       else            unexpected  throw exception

User · Answer

You can use two enums  One for the database and the other for readability   You just need to make sure they stay in sync  which seems like a small cost  You don t have to set the values  just set the positions the same  but setting the values makes it very clear the two enums are related and prevents errors from rearranging the enum members  And a comment lets the maintenance crew know these are related and must be kept in sync      keep in sync with GroupTypes public enum GroupTypeCodes       OEM      CMB       keep in sync with GroupTypesCodes public enum GroupTypes       TheGroup   GroupTypeCodes OEM      TheOtherGroup   GroupTypeCodes CMB     To use it you just convert to the code first   GroupTypes myGroupType   GroupTypes TheGroup  string valueToSaveIntoDatabase     GroupTypeCodes myGroupType  ToString      Then if you want to make it even more convenient you can add an extension function that only works for this type of enum   public static string ToString this GroupTypes source        return   GroupTypeCodes source  ToString        and you can then just do   GroupTypes myGroupType   GroupTypes TheGroup  string valueToSaveIntoDatabase   myGroupType ToString

User · Answer

You can add attributes to the items in the enumeration and then use reflection to get the values from the attributes   You would have to use the  field  specifier to apply the attributes  like so   enum GroupTypes        field Description  OEM        TheGroup        field Description  CMB        TheOtherGroup     You would then reflect on the static fields of the type of the enum  in this case GroupTypes  and get the DescriptionAttribute for the value you were looking for using reflection   public static DescriptionAttribute GetEnumDescriptionAttribute lt T gt       this T value  where T   struct          The type of the enum  it will be reused      Type type   typeof T           If T is not an enum  get out      if   type IsEnum           throw new InvalidOperationException               The type parameter T must be an enum type             If the value isn t defined throw an exception      if   Enum IsDefined type  value           throw new InvalidEnumArgumentException               value   Convert ToInt32 value   type           Get the static field for the value      FieldInfo fi   type GetField value ToString             BindingFlags Static   BindingFlags Public           Get the description attribute  if there is one      return fi GetCustomAttributes typeof DescriptionAttribute   true           Cast lt DescriptionAttribute gt    SingleOrDefault        I opted to return the DescriptionAttribute itself above  in the event that you want to be able to determine whether or not the attribute is even applied

User · Answer

I wanted to avoid using string literals completely  and also I didn t need to have space in item descriptions  More importantly  I wanted to have a mechanism to check if the provided string is a valid item  so I came up with this solution   public class Seasons       public static string Spring   get        public static string Summer   get        public static string Fall   get        public static string Winter   get         public static bool IsValid string propertyName                if  string IsNullOrEmpty propertyName                         return false                     try                                  return typeof Seasons  GetProperty propertyName     null                    catch                       return false                             And here is how it works   void Main         string s   nameof Seasons Fall       Console WriteLine   Fall is valid   Seasons IsValid s         true      s    WrongSeason       Console WriteLine   WrongSeason is valid   Seasons IsValid s         false     I tried to refactor IsValid   into a base class and use reflection to read the type  MethodBase GetCurrentMethod   DeclaringType   but since I wanted to have it static  it returns the base class type  not the inherited type  Your remedy to this will be very welcomed  Here is what I was trying to achieve   public  class Seasons   ConstantStringsBase              same    public  class ConstantStringsBase       public static bool IsValid string propertyName                       return MethodBase GetCurrentMethod   DeclaringType GetProperty propertyName     null

User · Answer

public class DataType       private readonly string value      private static readonly Dictionary lt string  DataType gt  predefinedValues       public static readonly DataType Json   new DataType  json        public static readonly DataType Xml   new DataType  xml        public static readonly DataType Text   new DataType  text        public static readonly DataType Html   new DataType  html        public static readonly DataType Binary   new DataType  binary         static DataType                 predefinedValues   new Dictionary lt string  DataType gt             predefinedValues Add Json Value  Json           predefinedValues Add Xml Value  Xml           predefinedValues Add Text Value  Text           predefinedValues Add Html Value  Html           predefinedValues Add Binary Value  Binary              private DataType string value                this value   value             public static DataType Parse string value                var exception   new FormatException   Invalid value for type  nameof DataType              if  string IsNullOrEmpty value               throw exception           string key   value ToLower            if   predefinedValues ContainsKey key               throw exception           return predefinedValues key              public string Value               get   return value

User · Answer

I would just create a dictionary and use the code as the key   Edit  To address the comment about doing a reverse lookup  finding the key   this would not be terribly efficient   If this is necessary  I would write a new class to handle it

User · Answer

I ve done something like this   public enum BusinessUnits       NEW EQUIPMENT   0      USED EQUIPMENT   1      RENTAL EQUIPMENT   2      PARTS   3      SERVICE   4      OPERATOR TRAINING   5    public class BusinessUnitService       public static string StringBusinessUnits BusinessUnits BU                switch  BU                        case BusinessUnits NEW EQUIPMENT  return  NEW EQUIPMENT               case BusinessUnits USED EQUIPMENT  return  USED EQUIPMENT               case BusinessUnits RENTAL EQUIPMENT  return  RENTAL EQUIPMENT               case BusinessUnits PARTS  return  PARTS               case BusinessUnits SERVICE  return  SERVICE               case BusinessUnits OPERATOR TRAINING  return  OPERATOR TRAINING               default  return String Empty                      Call it with this   BusinessUnitService StringBusinessUnits BusinessUnits PARTS

User · Answer

Have you considered a lookup table using a Dictionary   enum GroupTypes       TheGroup      TheOtherGroup    Dictionary lt string  GroupTypes gt  GroupTypeLookup   new Dictionary lt string  GroupTypes gt        initialize lookup table  GroupTypeLookup Add  OEM   TheGroup   GroupTypeLookup Add  CMB   TheOtherGroup     You can then use GroupTypeLookup TryGetValue   to look up a string when you read it

User · Answer

I used a structure as alluded to in a previous answer  but did away with any complexity   To me  this was most like creating an enumeration of strings   It is used in the same manner that an enumeration is used        struct ViewTypes               public const string View1    Whatever string you like           public const string View2    another string           Example use      switch  some string variable              case ViewTypes View1     do something    break        case ViewTypes View2     do something else    break

User · Answer

C  doesn t support enumerated strings  but for most situations you can use a List or Dictionary to get the desired effect   E g  To print pass fail results   List lt string gt  PassFail   new List lt string gt     FAIL    PASS     bool result   true  Console WriteLine  Test1      PassFail result GetHashCode

User · Answer

You could also use the extension model   public enum MyEnum        Description  String 1        V1  1       Description  String 2        V2  2      Your Extension Class  public static class MyEnumExtensions       public static string ToDescriptionString this MyEnum val                DescriptionAttribute   attributes    DescriptionAttribute   val             GetType               GetField val ToString                GetCustomAttributes typeof DescriptionAttribute   false           return attributes Length  gt  0   attributes 0  Description   string Empty             usage   MyEnum myLocal   MyEnum V1  print myLocal ToDescriptionString

User · Answer

If I understand correctly  you need a conversion from string to enum   enum GroupTypes       Unknown   0      OEM   1      CMB   2   static GroupTypes StrToEnum string str       GroupTypes g   GroupTypes Unknown      try           object o   Enum Parse typeof GroupTypes   str  true           g    GroupTypes  o    0         catch             return g       then use it like this GroupTypes g1   StrToEnum  OEM    GroupTypes g2   StrToEnum  bad value      You can make it more fancy with generics for the enum type if you wish

User · Answer

Create a second enum  for your DB containing the following   enum DBGroupTypes       OEM   0      CMB   1     Now  you can use Enum Parse to retrieve the correct DBGroupTypes value from the strings  OEM  and  CMB   You can then convert those to int and retrieve the correct values from the right enumeration you want to use further in your model

User · Answer

Taken from  EvenMien and added in some of the comments   Also for my own use case   public struct AgentAction       private AgentAction string value    Value   value         public string Value   get  private set         public override string ToString                 return this Value             public static AgentAction Login   new AgentAction  Logout        public static AgentAction Logout   new AgentAction  Logout         public static implicit operator string AgentAction action    return action ToString

User · Answer

Use a class   Edit  Better example  class StarshipType       private string  Name      private static List lt StarshipType gt   StarshipTypes   new List lt StarshipType gt          public static readonly StarshipType Ultralight   new StarshipType  Ultralight        public static readonly StarshipType Light   new StarshipType  Light        public static readonly StarshipType Mediumweight   new StarshipType  Mediumweight        public static readonly StarshipType Heavy   new StarshipType  Heavy        public static readonly StarshipType Superheavy   new StarshipType  Superheavy         public string Name               get   return  Name            private set    Name   value               public static IList lt StarshipType gt  StarshipTypes               get   return  StarshipTypes               private StarshipType string name  int systemRatio                Name   name           StarshipTypes Add this              public static StarshipType Parse string toParse                foreach  StarshipType s in StarshipTypes                        if  toParse    s Name                  return s                    throw new FormatException  Could not parse string

User · Answer

I even implemented a few enums as suggested by  Even  via class X and public static X members   just to find out later that these days  starting  Net 4 5  there s the right ToString   method   Now I m reimplementing everything back to enums

User · Answer

I was basically looking for the Reflection answer by  ArthurC  Just to extend his answer a little bit  you can make it even better by having a generic function          If you want for a specific Enum     private static string EnumStringValue GroupTypes e                return EnumStringValue lt GroupTypes gt  e                 Generic     private static string EnumStringValue lt T gt  T enumInstance                return Enum GetName typeof T   enumInstance            Then you can just wrap whatever you have  EnumStringValue GroupTypes TheGroup     if you incorporate the top part   or  EnumStringValue lt GroupTypes gt  GroupTypes TheGroup     if you just use the generic

User · Answer

My first question - Do you have access to the Database itself   This should be normalized in the database  ideally  otherwise  any solution is going to be prone to error   In my experience  data fields full of  OEM  and  CMB  tend to wind up having things like  oem   and other  crap data  mixed in over time      If you can normalize it  you could use the key in the table containing the elements as your Enum  and you re done  with a much cleaner structure   If that s not available  I d make your Enum  and make a class to parse your string into the Enum for you   This would at least give you some flexibility in handling non-standard entries and much more flexibility for trapping or handling errors than doing any of the workarounds using Enum Parse Reflection etc   A dictionary would work  but could break down if you ever have case issues  etc   I d recommend writing a class so you can do      I renamed this to GroupType  since it sounds like each element has a single type    GroupType theType   GroupTypeParser GetGroupType theDBString     This preserves most of your readability without having to change the DB

User · Answer

Following the answer of  Even Mien I have tried to go a bit further and make it Generic  I seem to be almost there but one case still resist and I probably can simplify my code a bit  I post it here if anyone see how I could improve and especially make it works as I can t assign it from a string   So Far I have the following results           Console WriteLine TestEnum Test1    displays  TEST1           bool test    TEST1     TestEnum Test1    true          var test2   TestEnum Test1    is TestEnum and has value          string test3   TestEnum Test1    test3    TEST1           var test4   TestEnum Test1    TestEnum Test2    false          EnumType lt TestEnum gt  test5    TEST1     works fine            TestEnum test5    string   DOESN T compile             Where the magics happens    public abstract  class EnumType lt T gt   where T   EnumType lt T gt            public  string Value   get  set         protected EnumType string value                Value   value              public static implicit operator EnumType lt T gt  string s                if  All Any dt   gt  dt Value    s                         Type t   typeof T                ConstructorInfo ci   t GetConstructor BindingFlags Instance   BindingFlags NonPublic null  new Type     typeof string     null                return  T ci Invoke new object    s                      else                       return null                       public static implicit operator string EnumType lt T gt  dt                return dt  Value              public static bool operator    EnumType lt T gt  ct1  EnumType lt T gt  ct2                return  string ct1     string ct2             public static bool operator    EnumType lt T gt  ct1  EnumType lt T gt  ct2                return   ct1    ct2               public override bool Equals object obj                try                       return  string obj    Value                    catch                       return false                       public override int GetHashCode                 return Value GetHashCode               public static IEnumerable lt T gt  All        gt  typeof T  GetProperties           Where p   gt  p PropertyType    typeof T           Select x   gt   T x GetValue null  null           I only then have to declare this for my enums   public class TestEnum   EnumType lt TestEnum gt          private TestEnum string value    base value              public static TestEnum Test1   get   return new TestEnum  TEST1            public static TestEnum Test2   get   return new TestEnum  TEST2

User · Answer

Adding this class  public class DatabasePreference       public DatabasePreference  CallerMemberName  string preferenceName                 PreferenceName   preferenceName            public string PreferenceName      This work is using CallerMemberName to minimize the coding  Using     Declare names public static DatabasePreference ScannerDefaultFlashLight   new DatabasePreference    public static DatabasePreference ScannerQrCodes   new DatabasePreference    public static DatabasePreference Scanner1dCodes   new DatabasePreference      Test it   Console WriteLine ScannerDefaultFlashLight PreferenceName   Console WriteLine ScannerDefaultFlashLight Scanner1dCodes     output   ScannerDefaultFlashLight Scanner1dCodes

User · Answer

You can do it very easily actually   Use the following code   enum GroupTypes      OEM     CMB      Then when you want to get the string value of each enum element just use the following line of code   String oemString   Enum GetName typeof GroupTypes   GroupTypes OEM     I ve used this method successfully in the past  and I ve also used a constants class to hold string constants  both work out pretty well  but I tend to prefer this

User · Answer

New in  Net Core 3 0 C  8 0  if your work environment allows you to upgrade your project  is a short-hand switch statement that looks somewhat enum-ish  At the end of the day it s the same old boring switch statement we ve been using for years    Only real difference here is that the switch statement got a new suit   public static RGBColor FromRainbow Rainbow colorBand    gt  colorBand switch       Rainbow Red      gt  new RGBColor 0xFF  0x00  0x00       Rainbow Orange   gt  new RGBColor 0xFF  0x7F  0x00       Rainbow Yellow   gt  new RGBColor 0xFF  0xFF  0x00       Rainbow Green    gt  new RGBColor 0x00  0xFF  0x00       Rainbow Blue     gt  new RGBColor 0x00  0x00  0xFF       Rainbow Indigo   gt  new RGBColor 0x4B  0x00  0x82       Rainbow Violet   gt  new RGBColor 0x94  0x00  0xD3                        gt  throw new ArgumentException message   invalid enum value   paramName  nameof colorBand         You ll notice that the code above which I copied from here  is actually using an enum as a param   It s not exactly what you want  and trust me  I ve wanted something of similar to what the OP is requesting for a long time   but I actually feel like this is somewhat of an olive branch from MS  JMO   Hope it helps someone

User · Answer

Try adding constants to a static class  You don t end up with a Type  but you will have readable  organised constants   public static class GroupTypes        public const string TheGroup    OEM       public const string TheOtherGroup    CMB

User · Answer

Here is the extension method that I used to get the enum value as string  First here is the enum    public enum DatabaseEnvironment        Description  AzamSharpBlogDevDatabase        Development   1        Description  AzamSharpBlogQADatabase        QualityAssurance   2        Description  AzamSharpBlogTestDatabase         Test   3     The Description attribute came from System ComponentModel    And here is my extension method   public static string GetValueAsString this DatabaseEnvironment environment            get the field      var field   environment GetType   GetField environment ToString         var customAttributes   field GetCustomAttributes typeof  DescriptionAttribute   false        if customAttributes Length  gt  0                return  customAttributes 0  as DescriptionAttribute  Description              else               return environment ToString               Now  you can access the enum as string value using the following code     TestFixture  public class when getting value of enum        Test      public void should get the value as string                 Assert AreEqual  AzamSharpBlogTestDatabase  DatabaseEnvironment Test GetValueAsString

User · Answer

In VS 2015  you can use nameof  public class LogCategory       public static string Trace      public static string Debug      public static string Info      public static string Warning      public static string Error      Usage   Logger Write  This is almost like an enum    nameof LogCategory Info

User · Answer

This is a way to use it as a strongly typed parameter or as a string    public class ClassLikeEnum       public string Value               get          private set             ClassLikeEnum string value                 Value   value             public static implicit operator string ClassLikeEnum c                return c Value             public static readonly ClassLikeEnum C1   new ClassLikeEnum  RandomString1        public static readonly ClassLikeEnum C2   new ClassLikeEnum  RandomString2

User · Answer

A small tweak to Glennular Extension method  so you could use the extension on other things than just ENUM s   using System  using System ComponentModel  namespace Extensions       public static class T Extensions                lt summary gt              Gets the Description Attribute Value              lt  summary gt               lt typeparam name  T  gt Entity Type lt  typeparam gt               lt param name  val  gt Variable lt  param gt               lt returns gt The value of the Description Attribute or an Empty String lt  returns gt          public static string Description lt T gt  this T t                DescriptionAttribute   attributes    DescriptionAttribute   t GetType   GetField t ToString    GetCustomAttributes typeof DescriptionAttribute   false               return attributes Length  gt  0   attributes 0  Description   string Empty                      Or Using Linq  using System  using System ComponentModel  using System Linq   namespace Extensions     public static class T Extensions           public static string Description lt T gt  this T t    gt                DescriptionAttribute   t               GetType                 GetField t  ToString                  GetCustomAttributes typeof DescriptionAttribute   false                 Select a   gt  a  Description                FirstOrDefault                   string Empty

User · Answer

Another way to deal with the problem  is to have a enum and a array of strings that will map the enum values with the list of strings   public enum GroupTypes       TheGroup    0      TheOtherGroup     string   GroupTypesStr          OEM        CMB       you may use it something like this   Log Write GroupTypesStr  int GroupTypes TheOtherGroup      It will prompt CMB  PROS    Easy and clean code  High Performance  specially in comparison with those approaches that uses classes    CONS    Prone to mess up the list when editing it  but it will be okay for a short list

User · Answer

I like to use properties in a class instead of methods  since they look more enum-like   Here s a example for a Logger   public class LogCategory       private LogCategory string value    Value   value         public string Value   get  set         public static LogCategory Trace     get   return new LogCategory  Trace            public static LogCategory Debug     get   return new LogCategory  Debug            public static LogCategory Info      get   return new LogCategory  Info            public static LogCategory Warning   get   return new LogCategory  Warning            public static LogCategory Error     get   return new LogCategory  Error            Pass in type-safe string values as a parameter   public static void Write string message  LogCategory logCategory        var log   new LogEntry   Message   message        Logger Write log  logCategory Value       Usage   Logger Write  This is almost like an enum    LogCategory Info

User · Answer

I didn t need anything robust like storing the string in attributes  I just needed to turn something like MyEnum BillEveryWeek into  bill every week  or MyEnum UseLegacySystem into  use legacy system --basically split the enum by its camel-casing into individiual lower-case words   public static string UnCamelCase this Enum input  string delimiter        bool preserveCasing   false        var characters   input ToString   Select  x  i    gt                if  i  gt  0  amp  amp  char IsUpper x                       return delimiter   x ToString CultureInfo InvariantCulture                   return x ToString CultureInfo InvariantCulture                 var result   preserveCasing          string Concat characters           string Concat characters  ToLower         var lastComma   result LastIndexOf       StringComparison Ordinal        if  lastComma  gt  -1               result   result Remove lastComma  2  Insert lastComma    and                return result      MyEnum UseLegacySystem UnCamelCase   outputs  use legacy system   If you have multiple flags set  it will turn that into plain english  comma-delimited except an  and  in place of the last comma    var myCustomerBehaviour   MyEnum BillEveryWeek   MyEnum UseLegacySystem   MyEnum ChargeTaxes   Console WriteLine myCustomerBehaviour UnCamelCase       outputs  bill every week  use legacy system and charge taxes

User · Answer

Based in other opinions  this is what I come up with  This approach avoids having to type  Value where you want to get the constant value   I have a base class for all string enums like this   using System  using Newtonsoft Json    JsonConverter typeof ConstantConverter    public class StringEnum  IConvertible       public string Value   get  set         protected StringEnum string value                Value   value             public static implicit operator string StringEnum c                return c Value            public string ToString IFormatProvider provider                return Value             public TypeCode GetTypeCode                 throw new NotImplementedException               public bool ToBoolean IFormatProvider provider                throw new NotImplementedException                The same for all the rest of IConvertible methods     The JsonConverter is like this   using System  using Newtonsoft Json   class ConstantConverter   JsonConverter       public override bool CanConvert Type objectType                return true             public override object ReadJson JsonReader reader  Type objectType  object existingValue  JsonSerializer serializer                throw new NotImplementedException               public override void WriteJson JsonWriter writer  object value  JsonSerializer serializer                if  value    null                        serializer Serialize writer  null                     else                       serializer Serialize writer  value ToString                         And an actual string enum will be something like this   public sealed class Colors   StringEnum       public static Colors Red   get   return new Catalog  Red            public static Colors Yellow   get   return new Catalog  Yellow            public static Colors White   get   return new Catalog  White             private Colors string value    base value          And with this  you can just use Color Red to even serialize to json without using the Value property

User · Answer

I would make it into a class an avoid an enum altogether   And then with the usage of a typehandler you could create the object when you grab it from the db   IE     public class Group       public string Value  get  set        public Group  string value    Value   value         public static Group TheGroup     return new Group  OEM          public static Group OtherGroup     return new Group  CMB

[c#] Associating enums with strings in C#

Examples related to c#

Examples related to .net