Casting ints to enums in C#

Guessing about ‘why’ is always dangerous, but consider this:

enum Direction { North =1, East = 2, South = 4, West = 8 }
Direction ne = Direction.North | Direction.East;

int value = (int) ne; // value == 3
string text = ne.ToString();  // text == "3"

When the [Flags] attribute is put in front of the enum, that last line changes to

string text = ne.ToString();  // text == "North, East"