Anyone knows the default value for enums using the default keywords as in:
MyEnum myEnum = default(MyEnum);
Would it be the first item?
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4 Answers
It is the value produced by (myEnum)0. For example:
enum myEnum
{
foo = 100
bar = 0,
quux = 1
}
Then default(myEnum) would be myEnum.bar or the first member of the enum with value 0 if there is more than one member with value 0.
The value is 0 if no member of the enum is assigned (explicitly or implicitly) the value 0.
5 Comments
Joan Venge
Thanks, but what if there is no 0 defined? But they were 100, 99 and 1?
Richard Cook
Then it is 0. I updated my answer accordingly. See related thread: stackoverflow.com/questions/529929/…
Jim Mischel
If there's no 0 defined, the value is still 0. Remember than an enum is really just a thin typesafe wrapper around an integral type, giving you the ability to reference integral values by name.
Joan Venge
Thanks, so if there is no enum 0, you mean the value assigned really be 0 as in int (0)?
Joan Venge
@Jim: got it now from your comment.
It's a bit hard to understand your question, but the default value for an enum is zero, which may or may not be a valid value for the enumeration.
If you want default(MyEnum) to be the first value, you'd need to define your enumeration like this:
public enum MyEnum
{
First = 0,
Second,
Third
}
Comments
The expression default(T) is the equivalent of saying (T)0 for a generic parameter or concrete type which is an enum. This is true whether or not the enum defines an entry that has the numeric value 0.
enum E1 {
V1 = 1;
V2 = 2;
}
...
E1 local = default(E1);
switch (local) {
case E1.V1:
case E1.V2:
// Doesn't get hit
break;
default:
// Oops
break;
}
Comments
slapped this into vs2k10.....
with:
enum myEnum
{
a = 1,
b = 2,
c = 100
};
myEnum z = default(en);
produces: z == 0 which may or may not be a valid value of your enum (in this case, its not)
thus sayeth visual studio 2k10
