Get int value from enum in C

Question

I have a class called Questions  plural   In this class there is an enum called Question  singular  which looks like this   public enum Question       Role   2      ProjectFunding   3      TotalEmployee   4      NumberOfServers   5      TopBusinessConcern   6     In the Questions class I have a get int foo  function that returns a Questions object for that foo  Is there an easy way to get the integer value off the enum so I can do something like this Questions Get Question Role

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You should have used Type Casting as we can use in any other language  If your enum is like this- public enum Question       Role   2      ProjectFunding   3      TotalEmployee   4      NumberOfServers   5      TopBusinessConcern   6    And you need to cast to an int  then do this- Question q   Question Role                              int something    int  q   Re- In C   there are two types of casting   Implicit Casting  automatically  - converting a smaller type to a larger type size like-   char - gt  int - gt  long - gt  float - gt  double   Explicit Casting  manually  - converting a larger type to a smaller size type like-   double - gt  float - gt  long - gt  int - gt  char  More can be found in here

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I came up with this extension method that includes current language features  By using dynamic  I don t need to make this a generic method and specify the type which keeps the invocation simpler and consistent   public static class EnumEx       public static dynamic Value this Enum e                switch  e GetTypeCode                          case TypeCode Byte                                return  byte   IConvertible  e                             case TypeCode Int16                                return  short   IConvertible  e                             case TypeCode Int32                                return  int   IConvertible  e                             case TypeCode Int64                                return  long   IConvertible  e                             case TypeCode UInt16                                return  ushort   IConvertible  e                             case TypeCode UInt32                                return  uint   IConvertible  e                             case TypeCode UInt64                                return  ulong   IConvertible  e                             case TypeCode SByte                                return  sbyte   IConvertible  e                                   return 0

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Following is the extension method  public static string ToEnumString lt TEnum gt  this int enumValue        var enumString   enumValue ToString        if  Enum IsDefined typeof TEnum   enumValue                 enumString     TEnum  Enum ToObject typeof  TEnum   enumValue   ToString              return enumString

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int number   Question Role GetHashCode      number should have the value 2

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public enum QuestionType       Role   2      ProjectFunding   3      TotalEmployee   4      NumberOfServers   5      TopBusinessConcern   6        is a fine declaration   You do have to cast the result to int like so   int Question    int QuestionType Role   Otherwise  the type is still QuestionType   This level of strictness is the C  way    One alternative is to use a class declaration instead   public class QuestionType       public static int Role   2      public static int ProjectFunding   3      public static int TotalEmployee   4      public static int NumberOfServers   5      public static int TopBusinessConcern   6     It s less elegant to declare  but you don t need to cast it in code   int Question   QuestionType Role   Alternatively  you may feel more comfortable with Visual Basic  which caters for this type of expectation in many areas

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The example I would like to suggest  to get an  int  value from an enum   is  public enum Sample       Book   1       Pen   2       Pencil   3    int answer    int Sample Book    Now the answer will be 1

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will give you the a list with all the integer values of the enum   List enumValues   Enum GetValues typeof EnumClass   Cast   ToList

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If you want to get an integer for the enum value that is stored in a variable  for which the type would be Question  to use for example in a method  you can simply do this I wrote in this example    enum Talen       Engels   1  Italiaans   2  Portugees   3  Nederlands   4  Duits   5  Dens   6    Talen Geselecteerd       public void Form1         InitializeComponent       Geselecteerd   Talen Nederlands        You can use the Enum type as a parameter  so any enumeration from any enumerator can be used as parameter void VeranderenTitel Enum e        this Text   Convert ToInt32 e  ToString        This will change the window title to 4  because the variable Geselecteerd is Talen Nederlands  If I change it to Talen Portugees and call the method again  the text will change to 3

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My favourite hack with int or smaller enums   GetHashCode      For an enum  public enum Test       Min   Int32 MinValue      One   1      Max   Int32 MaxValue      This   var values   Enum GetValues typeof Test     foreach  var val in values        Console WriteLine val GetHashCode         Console WriteLine   int val        Console WriteLine val       outputs  one 1 1 max 2147483647 2147483647 min -2147483648 -2147483648   Disclaimer   It doesn t work for enums based on long

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On a related note  if you want to get the int value from System Enum  then given e here   Enum e   Question Role    You can use   int i   Convert ToInt32 e   int i    int  object e  int i    int Enum Parse e GetType    e ToString     int i    int Enum ToObject e GetType    e     The last two are plain ugly  I prefer the first one

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I have recently converted away from using enums in my code in favour of instead using classes with protected constructors and predefined static instances  thanks to Roelof - C  Ensure Valid Enum Values - Futureproof Method    In light of that  below s how I d now approach this issue  including implicit conversion to from int    public class Question          Attributes     protected int index      protected string name         Go with a dictionary to enforce unique index       protected static readonly ICollection lt Question gt  values   new Collection lt Question gt         protected static readonly IDictionary lt int Question gt  values   new Dictionary lt int Question gt             Define the  enum  values     public static readonly Question Role   new Question 2  Role        public static readonly Question ProjectFunding   new Question 3   Project Funding        public static readonly Question TotalEmployee   new Question 4   Total Employee        public static readonly Question NumberOfServers   new Question 5   Number of Servers        public static readonly Question TopBusinessConcern   new Question 6   Top Business Concern            Constructors     protected Question int index  string name                this index   index          this name   name          values Add index  this                 Easy int conversion     public static implicit operator int Question question    gt          question index    nb  if question is null this will return a null pointer exception      public static implicit operator Question int index    gt                  values TryGetValue index  out var question    question   null          Easy string conversion  also update ToString for the same effect      public override string ToString     gt          this name       public static implicit operator string Question question    gt          question  ToString         public static implicit operator Question string name    gt          name    null   null   values Values FirstOrDefault item   gt  name Equals item name  StringComparison CurrentCultureIgnoreCase             If you specifically want a Get int x  function  though not required given the implicit converstion      public Question Get int foo    gt          foo     implicit conversion will take care of the conversion for you      The advantage of this approach is you get everything you would have from the enum  but your code s now much more flexible  so should you need to perform different actions based on the value of Question  you can put logic into Question itself  i e  in the preferred OO fashion  as opposed to putting lots of case statements throughout your code to tackle each scenario     NB  Answer updated 2018-04-27 to make use of C  6 features  i e  declaration expressions and lambda expression body definitions   See revision history for original code   This has the benefit of making the definition a little less verbose  which had been one of the main complaints about this answer s approach

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It s easier than you think - an enum is already an int  It just needs to be reminded   int y    int Question Role  Console WriteLine y      Prints 2

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Use an extension method instead   public static class ExtensionMethods       public static int IntValue this Enum argEnum                return Convert ToInt32 argEnum             And the usage is slightly prettier   var intValue   Question Role IntValue

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One more way to do it   Console WriteLine  Name   0   Value   0 D    Question Role     It will result in   Name  Role  Value  2

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In Visual Basic  it should be   Public Enum Question     Role   2     ProjectFunding   3     TotalEmployee   4     NumberOfServers   5     TopBusinessConcern   6 End Enum  Private value As Integer   CInt Question Role

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Declare it as a static class having public constants   public static class Question       public const int Role   2      public const int ProjectFunding   3      public const int TotalEmployee   4      public const int NumberOfServers   5      public const int TopBusinessConcern   6      And then you can reference it as Question Role  and it always evaluates to an int or whatever you define it as

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Just cast the enum  e g   int something    int  Question Role    The above will work for the vast majority of enums you see in the wild  as the default underlying type for an enum is int   However  as cecilphillip points out  enums can have different underlying types  If an enum is declared as a uint  long  or ulong  it should be cast to the type of the enum  e g  for  enum StarsInMilkyWay long  Sun   1  V645Centauri   2    Wolf424B   2147483649     you should use  long something    long StarsInMilkyWay Wolf424B

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Since Enums can be any integral type  byte  int  short  etc    a more robust way to get the underlying integral value of the enum would be to make use of the GetTypeCode method in conjunction with the Convert class   enum Sides       Left  Right  Top  Bottom   Sides side   Sides Bottom   object val   Convert ChangeType side  side GetTypeCode     Console WriteLine val     This should work regardless of the underlying integral type

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Try this one instead of convert enum to int   public static class ReturnType       public static readonly int Success   1      public static readonly int Duplicate   2      public static readonly int Error   -1

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Maybe I missed it  but has anyone tried a simple generic extension method   This works great for me  You can avoid the type cast in your API this way but ultimately it results in a change type operation  This is a good case for programming Roslyn to have the compiler make a GetValue lt T  method for you       public static void Main                 int test   MyCSharpWrapperMethod TestEnum Test1            Debug Assert test    1              public static int MyCSharpWrapperMethod TestEnum customFlag                return MyCPlusPlusMethod customFlag GetValue lt int gt                 public static int MyCPlusPlusMethod int customFlag                   Pretend you made a PInvoke or COM  call to C   method that require an integer         return customFlag             public enum TestEnum               Test1   1          Test2   2          Test3   3          public static class EnumExtensions       public static T GetValue lt T gt  this Enum enumeration                T result   default T            try                       result    T Convert ChangeType enumeration  typeof T                      catch  Exception ex                        Debug Assert false               Debug WriteLine ex                      return result

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To ensure an enum value exists and then parse it  you can also do the following      Fake Day of Week string strDOWFake    SuperDay       Real Day of Week string strDOWReal    Friday       Will hold which ever is the real DOW  DayOfWeek enmDOW      See if fake DOW is defined in the DayOfWeek enumeration  if  Enum IsDefined typeof DayOfWeek   strDOWFake            This will never be reached since  SuperDay         doesn t exist in the DayOfWeek enumeration      enmDOW    DayOfWeek Enum Parse typeof DayOfWeek   strDOWFake        See if real DOW is defined in the DayOfWeek enumeration  else if  Enum IsDefined typeof DayOfWeek   strDOWReal            This will parse the string into it s corresponding DOW enum object      enmDOW    DayOfWeek Enum Parse typeof DayOfWeek   strDOWReal         Can now use the DOW enum object  Console Write  Today is     enmDOW ToString

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Since enums can be declared with multiple primitive types  a generic extension method to cast any enum type can be useful   enum Box       HEIGHT      WIDTH      DEPTH    public static void UseEnum         int height   Box HEIGHT GetEnumValue lt int gt         int width   Box WIDTH GetEnumValue lt int gt         int depth   Box DEPTH GetEnumValue lt int gt        public static T GetEnumValue lt T gt  this object e    gt   T e

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Example  public enum EmpNo       Raj   1      Rahul      Priyanka    And in the code behind to get the enum value  int setempNo    int EmpNo Raj     This will give setempNo   1  or int setempNo    int EmpNo Rahul     This will give setempNo   2  Enums will increment by 1  and you can set the start value  If you don t set the start value it will be assigned as 0 initially

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public enum Suit   int       Spades   0      Hearts   1      Clubs   2      Diamonds   3    Console WriteLine  int  Suit Enum Parse typeof Suit    Clubs         From int Console WriteLine  Suit 1       From a number you can also Console WriteLine  Suit Enum ToObject typeof Suit   1     if  typeof Suit  IsEnumDefined  Spades          var res    int  Suit Enum Parse typeof Suit    Spades        Console Out WriteLine   0    res

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Use   Question question   Question Role  int value   question GetHashCode      It will result in value    2   This is only true if the enum fits inside an int

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You can do this by implementing an extension method to your defined enum type   public static class MyExtensions       public static int getNumberValue this Question questionThis                return  int questionThis            This simplifies getting the int value of the current enum value   Question question   Question Role  int value   question getNumberValue      or  int value   Question Role getNumberValue

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Use   Question question   Question Role  int value   Convert ToInt32 question

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The easiest solution I can think of is overloading the Get int  method like this    modifiers  Questions Get Question q        return Get  int q       where  modifiers  can generally be same as for the Get int  method  If you can t edit the Questions class or for some reason don t want to  you can overload the method by writing an extension   public static class Extensions       public static Questions Get this Questions qs  Question q                return qs Get  int q

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Question question   Question Role  int value    int  question    Will result in value    2

[c#] Get int value from enum in C#

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