Convert Enum into underlying type

Question

I have an enum as follows

type Suit =
    |Clubs = 'C'
    |Spades = 'S'
    |Hearts = 'H'
    |Diamonds = 'D'

How do I get the underlying char value if given enum value? eg I have Suit.Clubs and want to get 'C'

Answer 1

as another option

type Suit =
    |Clubs = 'C'
    |Spades = 'S'
    |Hearts = 'H'
    |Diamonds = 'D'

let c = Suit.Clubs
let v : char = LanguagePrimitives.EnumToValue c

EDITED: Comparison of different approaches:

type Suit =
    |Clubs = 'C'
    |Spades = 'S'
    |Hearts = 'H'
    |Diamonds = 'D'

let valueOf1 (e : Suit) = LanguagePrimitives.EnumToValue e
let valueOf2 (e : Suit) = unbox<char> e
let valueOf3 (e : Suit) = (box e) :?> char

And under the hood:

.method public static 
    char valueOf1 (
        valuetype Program/Suit e
    ) cil managed 
{
    // Method begins at RVA 0x2050
    // Code size 3 (0x3)
    .maxstack 8

    IL_0000: nop
    IL_0001: ldarg.0
    IL_0002: ret
} // end of method Program::valueOf1


.method public static 
    char valueOf2 (
        valuetype Program/Suit e
    ) cil managed 
{
    // Method begins at RVA 0x2054
    // Code size 13 (0xd)
    .maxstack 8

    IL_0000: nop
    IL_0001: ldarg.0
    IL_0002: box Program/Suit
    IL_0007: unbox.any [mscorlib]System.Char
    IL_000c: ret
} // end of method Program::valueOf2

.method public static 
    char valueOf3 (
        valuetype Program/Suit e
    ) cil managed 
{
    // Method begins at RVA 0x2064
    // Code size 13 (0xd)
    .maxstack 8

    IL_0000: nop
    IL_0001: ldarg.0
    IL_0002: box Program/Suit
    IL_0007: unbox.any [mscorlib]System.Char
    IL_000c: ret
} // end of method Program::valueOf3

Answer 2

You can use functions from the LanguagePrimitives module:

// Convert enum value to the underlying char value
let ch = LanguagePrimitives.EnumToValue Suit.Clubs

// Convert the char value back to enum
let suit = LanguagePrimitives.EnumOfValue ch

EDIT: I didn't see these functions in my first answer attempt, so I first suggested using:

unbox<char> Suit.Clubs

This is shorter than what ildjarn suggests in a comment, but it has the same problem - there is no checking that you're actually converting to the right type. With EnumToValue, you cannot make this mistake, because it always returns the value of the right underlying type.