Why we can't have "char" enum types

The default type is int. More information at the C# reference at MSDN. You can also find a link to the C# language specification at MSDN. I think the reason for the restriction probably derives from these statements in the language specification, section 4.1.5.

The char type is classified as an integral type, but it differs from the other integral types in two ways:

• There are no implicit conversions from other types to the char type. In particular, even though the sbyte, byte, and ushort types have ranges of values that are fully representable using the char type, implicit conversions from sbyte, byte, or ushort to char do not exist.

• Constants of the char type must be written as character-literals or as integer-literals in combination with a cast to type char. For example, (char)10 is the same as '\x000A'.

Technically, you can't do this. But, you can convert the enum to a byte and then convert that to char. This is useful if your goal is to have something like this (realizing this is impossible to do:

public enum CharEnum
{
    one = '1'
}

You can do this, however, by using ASCII byte values and then converting:

public enum CharEnum
{
    one = 49,
    two = 50
}

You can then convert to byte and to char to get the char value. It is not really pretty, but it will work, if getting a char is your ultimate goal. You can also use unicode and an int value, if you need chars outside of the ASCII range. :-)

See ECMA standard 335, Common Language Infrastructure (CLI), in Ecma International. The CLI allows the underlying type to be char or bool but C# and VB.Net don't allow it. For what it is worth, C++/CLI does allow System::Char as the underlying type.

I presume that C# and VB.Net don't allow char and bool as the underlying type for syntactical reasons only.

char charPC = 'P';
if (Enum.IsDefined(typeof(PayCode), (PayCode)charPC)) { 
        // check if charPC is a valid value
        PayCode enumPC = (PayCode)charPC; // enumPC == PayCode.Paid
}

• Made a small change, no need to convert it to an (int) in the if for all cases, depends on the enum type. But if you cast it directly to the enum type itself, it should always work.

Targeting VB.NET and CLI consumers, you can compile the char enum like this (easiest with a VB.NET or C# project that has IL Support (an extension) enabled):

.class public auto ansi sealed Hafner.Testing.EdgeCase.CharEnum
       extends [mscorlib]System.Enum
{
    .field public specialname rtspecialname char value__
    .field public static literal valuetype Hafner.Testing.EdgeCase.CharEnum Min = char(0)
    .field public static literal valuetype Hafner.Testing.EdgeCase.CharEnum Zero = char(0)
    .field public static literal valuetype Hafner.Testing.EdgeCase.CharEnum Max = char(65535)
    .field public static literal valuetype Hafner.Testing.EdgeCase.CharEnum DuplicateSameValue = char(65) //A
    .field public static literal valuetype Hafner.Testing.EdgeCase.CharEnum duplicateSameValue = char(65) //A
    .field public static literal valuetype Hafner.Testing.EdgeCase.CharEnum DuplicateOtherValue = char(90) //Z
    .field public static literal valuetype Hafner.Testing.EdgeCase.CharEnum duplicateOtherValue = char(88) //X

}

Character enums would simply be strings wouldn't they? I'm not sure what other benefit you would derive from a character enumeration?

As others have said, the default type is int for an enumeration.