Get int value from enum in C#

Asked 2023-09-20 20:33:42 View 802,860

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)?

Answers

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;

Answered   2023-09-20 20:33:42

  • @Harry it isn't true. You can create Enumeration without casting, it is not required. and I only assign number in special cases, most of the time, I leave it as default value. but you can do enum Test { Item = 1 } and see that 1 == (int)Test.Item is equal. - anyone
  • @Jaider (int)Test.Item That is a cast! () is the explicit cast operator. - anyone
  • @Sinthia V he said you can create it without casting, which is correct - anyone
  • If the underlying type for enum Question was not int but long this cast will truncate Roles integral value! - anyone
  • When you accept an Enum as a parameter, you know is only a fixed number of possible integral values you can get. On the other hand, if you take simply an int, then you have to validate if that int is within the accepted values., thus complicating the code. You can always override your signatures like ``` public void MyMethod(int x) { // do something with x } public void MyMethod(Enum x) { this.MyMethod((int) x); } ```` - anyone

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.

Answered   2023-09-20 20:33:42

  • This technique proved its worth to me when dealing with a generic type where T:enum (actually T:struct, IConvertible but that's a different story). - anyone
  • How would you modify this to print out the hexadecimal value of side? This example shows the decimal value. The problem is that var is of type object, so you need to unbox it and it gets messier than I would like. - anyone
  • If you want to convert to int try (in case of an enum Sides : int) [...] object val = Convert.ChangeType(side, typeof(int)); [...] - anyone
  • @TimAbell All I can really say is that we found that dynamically compiled aspx pages (where you have to deploy the .cs files to the live server) were assigning the integers differently to each value. That meant that serialised objects one one machine, were deserialising with different values on a different machine and effectively getting corrupted (causing hours of confusion). We raised it with MS and I seem to recall they said that the autogenerated integers were not guaranteed to be the same when built across different framework versions. - anyone
  • @TimAbell On a separate occasion, a developer deleted an obsolete/unused Enum value causing all other values in the sequence to be out by one. As such, our coding standards now require that IDs are always specified explicitly, otherwise adding/deleting or even auto-formatting the code (e.g. sorting alphabetically) will change all the values causing data corruption. I would strongly advise anyone to specify all Enum integers explicitly. This is ultra-important if they correlate to externally (database) stored values. - anyone

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.

Answered   2023-09-20 20:33:42

  • I'd use static readonly int because constants are compiled into their hard values. See stackoverflow.com/a/755693/492 - anyone
  • This solution actually doesn't provide the real benefit of strongly typed enums. If I only wanted to pass a GameState-enum-parameter to a specific method for example, the compiler shouldn't allow me to pass any int-variable as a parameter. - anyone
  • @CADBloke which is precisely why you would use const and not static readonly because every time you compare static readonly you're making a method call to get the value of the variable whereas with a const you're comparing two value types directly. - anyone
  • @brettof86 Yes, a const would be faster, if the compilation limitation will never be problem then it's all good. - anyone
  • @Zack I didn't explain that very well, by compilation limitation I mean that the value is hard-coded when you compile it so any change to that value would require that all assemblies using it need to be recompiled. I'm inclined to agree with you about usage because changing the values would have far-reaching implications. - anyone

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.

Answered   2023-09-20 20:33:42

  • The second one is the fastest though. - anyone
  • As someone who is used to using Mixins in Minecraft modding, the second seems like the obvious winner. - anyone
  • And the 5th option (as the most answers says) is: int i = (int)e; (without casting to object first) - anyone
  • @andreyk2Hohlov Cannot convert type 'System.Enum' to 'int' - anyone
Question question = Question.Role;
int value = (int) question;

Will result in value == 2.

Answered   2023-09-20 20:33:42

  • So something like this Questions.Get(Convert.ToInt16(Question.Applications)) - anyone
  • You can simply cast in either direction; the only thing to watch is that enums don't enforce anything (the enum value could be 288, even though no Question exists with that number) - anyone
  • @jim: No, just cast the value: Questions.Get((int)Question.Applications); - anyone

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.

Answered   2023-09-20 20:33:42

  • Can something that is a Raj be also be a Rahul or a Priyanka? Your values conflict and should double to be unique e.g. 0, 1, 2, 4, 8, etc. This is my core concern with enums. - anyone
  • @TimothyGonzalez actually enums simply count 1 up if you don't explicitly specify their value ;) - anyone
  • @derHugo that depends if you assume the numerical values to be base 10 or base 2. - anyone
  • @TimothyGonzalez well there is not much to assume ... I just pointed out that by default they do just count up 1 in int except you explicitly define otherwise - anyone

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

Answered   2023-09-20 20:33:42

  • Nitpick: this enum is already an int. Other enums might be different types -- try "enum SmallEnum : byte { A, B, C }" - anyone
  • Absolutely true. C# reference: "Every enumeration type has an underlying type, which can be any integral type except char." - anyone

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<Question> values = new Collection<Question>();
    protected static readonly IDictionary<int,Question> values = new Dictionary<int,Question>();

    // 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) =>
        question.index; //nb: if question is null this will return a null pointer exception

    public static implicit operator Question(int index) =>        
        values.TryGetValue(index, out var question) ? question : null;

    // Easy string conversion (also update ToString for the same effect)
    public override string ToString() =>
        this.name;

    public static implicit operator string(Question question) =>
        question?.ToString();

    public static implicit operator Question(string name) =>
        name == null ? null : values.Values.FirstOrDefault(item => 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) =>
        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.

Answered   2023-09-20 20:33:42

  • I guess it's the trade off between explicit cast and the code you have to write to circumvent it. Still love the implementation just wish it wasn't so lengthy. +1 - anyone
  • I've used several different type of classes structured similar to this. I find they work wonders when trying to follow the "don't let me be an idiot later" methodology. - anyone
  • ps. Those who like this approach may be interested in github.com/ardalis/SmartEnum; a generic class aimed at giving enum like functionality to classes defined in the above way. - anyone

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.

Answered   2023-09-20 20:33:42

  • Unfortunately, this approach gives poor performance the more you use it. I tried it in some code of mine, and as time went on, my application got slower and slower, with less and less CPU usage. This implied that the threads were waiting on something - I'm assuming some kind of garbage collection, possibly due to boxing the enum parameter to ToInt32(). By switching to a simple int.Parse(), I was able to eliminate this poor performance completely, and the performance stayed the same no matter how long the code ran. - anyone

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();

Answered   2023-09-20 20:33:42

One more way to do it:

Console.WriteLine("Name: {0}, Value: {0:D}", Question.Role);

It will result in:

Name: Role, Value: 2

Answered   2023-09-20 20:33:42

  • This was the best solution for my use case, as my enums were mix of int and long values - anyone

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() + ".");

Answered   2023-09-20 20:33:42

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.

Answered   2023-09-20 20:33:42

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.

Answered   2023-09-20 20:33:42

  • This is only true if the enum fits inside an int of course, as GetHashCode returns an integer. - anyone

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<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<int>());
    }

    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<T>(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;
    }
}

Answered   2023-09-20 20:33:42

  • Possibly because doing (int)customFlag is less typing all around and does more or less the same thing? - anyone
  • Re "Maybe I missed it, but has anyone tried a simple generic extension method?": SixOThree said "Use an extension method instead" and Bronek said "You can do this by implementing an extension method to your defined enum type". - anyone
int number = Question.Role.GetHashCode();

number should have the value 2.

Answered   2023-09-20 20:33:42

  • GetHashCode is one way to get value from Enum common mask - anyone
  • Note that this is only "legit" for bool*, byte, ushort, int, and uint**. The GetHashCode for other types modifies the value, e.g. does some bitshifts and xors. (* 1 / 0, **casted to int of course). But all in all just don't do this unless it's your own private code. - anyone

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();

Answered   2023-09-20 20:33:42

  • Bronek, what you did is make up uninformative syntax through a (non generic btw) extension method that actually takes longer to write. I fail to see how it is better than the original solution by Tetraneutron. Let us not make this into a chat, help is always welcome in stackoverflow and everyone here is here to help. Please take my comment as constructive criticism. - anyone
  • Benjamin,first of all,why did you delete my comment?I don't understand your decisions-maybe somebody else through the community would agree with my comment.Secondly,my solution wraps Tetraneutron's one and accurately it is easier and less writing because an extension method is suggested by IntelliSense.So I think your decision is not impartial and representative.I see many similar answering on Stack and it is OK.Anyway I use my solution and maybe there are some people would choose my solution in the future,but these negative points make it harder to find.Most of all it is correct and not copy. - anyone
  • @Bronek If you don't ping me I get no indication that you replied. I did not delete your comment I do not have the ability or want to do so. Likely a mod came by and deleted it - you're welcome to flag it for moderator attention and ask why or better yet - ask on Meta Stack Overflow. I have an opinion about your solution from a programming stand point which is perfectly in my right - this is what comments are for to begin with, no need to take it personal. - anyone
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);
}

Answered   2023-09-20 20:33:42

  • An explanation of the sample code would be in order (by editing your answer, not here in comments). - anyone
  • zero is generally reserved for unset / unkown state in enums, unusual to define it like that - anyone

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<int>();
    int width = Box.WIDTH.GetEnumValue<int>();
    int depth = Box.DEPTH.GetEnumValue<int>();
}

public static T GetEnumValue<T>(this object e) => (T)e;

Answered   2023-09-20 20:33:42

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 -> int -> long -> float -> double

  • Explicit Casting (manually) - converting a larger type to a smaller size type like-

double -> float -> long -> int -> char

More can be found in here.

Answered   2023-09-20 20:33:42

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);
    }
}

Answered   2023-09-20 20:33:42

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.

Answered   2023-09-20 20:33:42

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.

Answered   2023-09-20 20:33:42

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;        
}

Answered   2023-09-20 20:33:42

Following is the extension method

public static string ToEnumString<TEnum>(this int enumValue)
{
    var enumString = enumValue.ToString();
    if (Enum.IsDefined(typeof(TEnum), enumValue))
    {
        enumString = ((TEnum) Enum.ToObject(typeof (TEnum), enumValue)).ToString();
    }
    return enumString;
}

Answered   2023-09-20 20:33:42

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)

Answered   2023-09-20 20:33:42

will give you the a list with all the integer values of the enum :

List enumValues = Enum.GetValues(typeof(EnumClass)).Cast().ToList();

Answered   2023-09-20 20:33:42

public enum ViewType
{
    List = 1,
    Table = 2,
};
            
// You can use the Enum type as a parameter, so any enumeration from any enumerator 
// cshtml
// using proyects.Helpers
// @if (Model.ViewType== (int)<variable>.List )

Answered   2023-09-20 20:33:42

Nearly all of the current answers use Convert or cast to object before the target type, which results in boxing and unboxing operations. This causes heap allocations and may not be acceptable for hot paths.

Since the majority of these answers were written, System.Runtime.CompilerServices.Unsafe was introduced, enabling low-level manipulation of pointers.

In combination with generics, the Unsafe class allows us to change the underlying type of the System.Enum parameter safely, with zero allocations, and with performance that is nearly indistinguishable from an empty method duration:

public long GetEnumValue<T>(T enumInstance) where T : unmanaged, Enum
{
    var size = Unsafe.SizeOf<T>();
    
    if (size == Unsafe.SizeOf<byte>())
    {
        return Unsafe.As<T, byte>(ref enumInstance);
    }
    else if (size == Unsafe.SizeOf<short>())
    {
        return Unsafe.As<T, short>(ref enumInstance);
    }
    else if (size == Unsafe.SizeOf<int>())
    {
        return Unsafe.As<T, int>(ref enumInstance); 
    }
    else if (size == Unsafe.SizeOf<long>())
    {
        return Unsafe.As<T, long>(ref enumInstance);
    }
    
    return -1; // or throw if you prefer
}

Convert vs Unsafe benchmark


If it is preferable to always return an int, you can do so, although if the backing field of the enum exceeds int.MaxValue, it will overflow:

public int GetEnumValue<T>(T enumInstance) where T : unmanaged, Enum
{
    var size = Unsafe.SizeOf<T>();
    
    if (size == Unsafe.SizeOf<byte>())
    {
        return Unsafe.As<T, byte>(ref enumInstance);
    }
    else if (size == Unsafe.SizeOf<short>())
    {
        return Unsafe.As<T, short>(ref enumInstance);
    }
    else if (size == Unsafe.SizeOf<int>())
    {
        return Unsafe.As<T, int>(ref enumInstance); 
    }
    else if (size == Unsafe.SizeOf<long>())
    {
        return Unsafe.As<T, int>(ref enumInstance);
    }
    
    return -1; // or throw if you prefer
}

If the following were used:

public enum EnumLong : long
{
    First,
    Second,
    Third = (long)(int.MaxValue) + 1
}

var val = GetEnumValue(EnumLong.Third);

-2147483648 would be returned due to an overflow. It is extremely unlikely that developers would create enums with such large flag values, but is always a possibility.

Answered   2023-09-20 20:33:42

public int QuestionToInt(Question q)
{
    return (int)q;
}

Answered   2023-09-20 20:33:42

  • Is it better to define a whole new function for this when you can just cast it? - anyone