How to get the underlying value of an enum

Question

I have the following enum declared:

 public enum TransactionTypeCode { Shipment = 'S', Receipt = 'R' }

How do I get the value 'S' from a TransactionTypeCode.Shipment or 'R' from TransactionTypeCode.Receipt ?

Simply doing TransactionTypeCode.ToString() gives a string of the Enum name "Shipment" or "Receipt" so it doesn't cut the mustard.

Solution 1

Marking this as not correct, but I can't delete it.

Try this:

string value = (string)TransactionTypeCode.Shipment;

Solution 2

You have to check the underlying type of the enumeration and then convert to a proper type:

public enum SuperTasks : int
    {
        Sleep = 5,
        Walk = 7,
        Run = 9
    }

    private void btnTestEnumWithReflection_Click(object sender, EventArgs e)
    {
        SuperTasks task = SuperTasks.Walk;
        Type underlyingType = Enum.GetUnderlyingType(task.GetType());
        object value = Convert.ChangeType(task, underlyingType); // x will be int
    }    

Solution 3

I believe Enum.GetValues() is what you're looking for.

Solution 4

The underlying type of your enum is still int, just that there's an implicit conversion from char to int for some reason. Your enum is equivalent to

TransactionTypeCode { Shipment = 83, Receipt = 82, }

Also note that enum can have any integral type as underlying type except char, probably for some semantic reason. This is not possible:

TransactionTypeCode : char { Shipment = 'S', Receipt = 'R', }

---

To get the char value back, you can just use a cast.

var value = (char)TransactionTypeCode.Shipment;

// or to make it more explicit:
var value = Convert.ToChar(TransactionTypeCode.Shipment);

The second one causes boxing, and hence should preform worse. So may be slightly better is

var value = Convert.ToChar((int)TransactionTypeCode.Shipment);

but ugly. Given performance/readability trade-off I prefer the first (cast) version..

View more solutions

Comments

[Abhishek]

Actually its a little more complex, I copied the code wrong from my sample, you cannot have strings for values in an enum. so the full answer would be ((char)instance.Shipment),ToString()

[Abhishek]

I suppose if you don't know the underlying type of the enum this would be the way to do it. But how you would ever end up in that situation is beyond me.

[jimr]

+1 This is the last step I needed to automatically (through reflection) create my SP parameter-value list from an entity object. I can't save the enum to the database, so I'm saving the underlying value.

[Jeppe Stig Nielsen]

@GeorgeMauer The "underlying type" of your enum is still int, so your definition really says: enum TransactionTypeCode { Shipment = 83, Receipt = 82, }. There's an implicit conversion from char to int, for some reason. The only "problem" (which might be not a problem) with your enum is that default(TransactionTypeCode) does not have a name, since no member equals 0 (or '\0').

[kingfleur]

The Convert.ChangeType does need a FormatProvider, but for enums (which are basically ints), I think you can just pass null. +1 for the tip. @GeorgeMauer: I ended up with such a situation in SterlingDB, where all kind of types are serialzed to a file. So an object is passed to the serialize method. If it's an enum, we'll serialize the integer value, so we need the underlying value.

[C.Evenhuis]

@Peter whether Convert.ChangeType requires an IFormatProvider depends on the framework you're working with. @GeorgeMauer I had to use it when communicating between AppDomains where only one of them could load the enum type.

[Kirk Woll]

This answer is categorically wrong on every level. Start with the fact that it won't compile, and continue on to the fact that enums aren't strings, that characters aren't strings, and that the underlying type of the enum is not -- and cannot be -- a string.

[Jens]

OP tagged the question C# your code looks like java to me

[Paul Childs]

-1 This implies you know the ordering of the enum internally. E.g., one would be very much misled by this solution if they expected Shipment to be the first value of the enum.

[Paul Childs]

@GeorgeMauer all you need for that situation is peopleWorkingOnCodeBase > 1 || IsFinite(abilityToRememberImplicationsOfUnderlyingTypeDecisi‌​on)