Flags enum attribute

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C#

enum Suits { Spades = 1, Clubs = 2, Diamonds = 4, Hearts = 8 }

...

var str1 = (Suits.Spades | Suits.Diamonds).ToString();
           // "5"

Why it is "5"? I don't understand it.

Posted 12-Feb-15 11:10am

zhshqzyc

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Sergey Alexandrovich Kryukov 12-Feb-15 19:25pm

What would you expect? Do you at least understand why 1 | 4 == 5? Or your confusion is only about the string?
—SA

4 solutions

Solution 4

In addition to Solution 2:

Please see my comment to the question. The attribute System.FlagsAttribute affects only one thing: string representation of enumeration values, and, hence, all cases when such representation is used, such as debuggers. If does not affect any other functionality. Reflection examines your enumeration members' name and generates bit-combined names. If you are curious to know how such things work, you can read my article Enumeration Types do not Enumerate! Working around .NET and Language Limitations[^].

—SA

Posted 12-Feb-15 13:31pm

Sergey Alexandrovich Kryukov

Solution 3

Numbers in a computer are binary. Or symbol | is doing 001 OR 100 = 101 which is 5 in binary.

Posted 12-Feb-15 11:22am

BacchusBeale

Solution 2

Because you didn't use the FlagsAttribute.

Posted 12-Feb-15 11:21am

PIEBALDconsult

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Tomas Takac · Accepted Answer · 2015-02-12T11:20:00

Solution 1

Spades = 1 dec = 001 bin
Diamonds = 4 dec = 100 bin

| = bitwise or[^]

hence: 001 bin | 100 bin = 101 bin = 5 dec

Or you can think of it as adding a specific bit to the result. That's why flags[^] should always be defined as powers of 2.

Posted 12-Feb-15 11:20am

Tomas Takac

Comments

Tomas Takac 12-Feb-15 17:30pm

Why the down vote? I admit I'm not completely sure this is what the OP is asking but it's definitely not wrong.

PIEBALDconsult 12-Feb-15 19:41pm

I don't see any downvotes.