Neatest way to 'OR' all values in a Flagged Enum?

Question

Given the enum:

[Flags]
public enum mytest
{
    a = 1,
    b = 2,
    c = 4
}

I\'ve come up with two ways to represent all va

Answer 1

How about something like

var all = Enum.GetValues(typeof(MyEnum)).Cast().Last() * 2 - 1;

basically

all = max*2-1

this only works if all values are present from 1 to the max value.

1,2,4...32,64...