bitwise combination as integer to enum

Question

Currently i'm trying to parse a integer that is a bitwise combination to a enum from a third-party API. For example: i receive a integer with the value 1035 this value holds three enum values;

enum Status
    1= "Status 1" 
    2= "Status 2" 
    4= "Status 3" 
    8= "Status 4" 
    ........ 
    1024= "Status 8"
end enum

So i need a function that converts the value 1035 to Status 1 + Status 2 + Status 4 + Status 8

Tried to convert it to Bit and then use bit shifting but this doesn't give me the right results... Hopefully someone could help me out in C# or vb.net example.

Just cast it to the target enum.. if it has the `FlagsAttribute` it will be fine — Biesi, Jun 05 '18 at 07:46
One weird way would be to use the Binary string representation of the int to see the bit — Drag and Drop, Jun 05 '18 at 07:46
If you have the `enum` declared correctly, you can simply cast am `int` value as that type. — jmcilhinney, Jun 05 '18 at 07:46
Related : https://stackoverflow.com/questions/1285986/flags-enum-bitwise-operations-vs-string-of-bits — Drag and Drop, Jun 05 '18 at 07:47
@BiesiGrr, actually, it doesn't depend on the `Flags` attribute except in that that will show all the constituent values in the result of `ToString`. — jmcilhinney, Jun 05 '18 at 07:47
@BiesiGrr, yes it is, but `1 & 2 & 8 & 1024`, which is what the OP specified, is `1035`. — jmcilhinney, Jun 05 '18 at 07:49
1035 =0b10000001011 so the flag are 2^0, 2^1, 2^4, 2^10; One is talking about statue the other is talking about int value of the flag. but same — Drag and Drop, Jun 05 '18 at 07:49
the correct answer is 1035 is already Status 1 + Status 2 + Status 4 + Status 8. So what is the next step? — Drag and Drop, Jun 05 '18 at 07:51
Please do not add an answer within the question; it's what answer boxes are for. Either accept an answer posted, or post one yourself, but don't add it to the question. — Adriaan, Jun 05 '18 at 10:45

Matthew Watson · Accepted Answer · 2018-06-05T08:07:48.727

If you apply the [Flags] attribute to the enum, it will make the enum's ToString() return a string which indicates which bits are set - but I don't think that is going to be that useful to you, other than its role in documenting that the enum is a flags enum.

However, regardless of the presence of the [Flags] attribute, Enum.HasFlag() will tell you if the flag is set.

This sample console app should make it clear:

using System;

namespace Demo
{
    [Flags]
    enum Status
    {
        None     = 0,
        Status1  = 1,
        Status2  = 2,
        Status3  = 4,
        Status4  = 8,
        Status5  = 16,
        Status6  = 32,
        Status7  = 64,
        Status8  = 128,
        Status9  = 256,
        Status10 = 512,
        Status11 = 1024
    }

    class Program
    {
        static void Main()
        {
            Status s = (Status)1035;

            Console.WriteLine(s); // "Status1, Status2, Status4, Status11"

            if (s.HasFlag(Status.Status4))               // "Status 4 is set"
                Console.WriteLine("Status4 is set");
            else
                Console.WriteLine("Status4 is not set");

            if (s.HasFlag(Status.Status3))               // "Status 3 is not set"
                Console.WriteLine("Status3 is set");
            else
                Console.WriteLine("Status3 is not set");
        }
    }
}

Note: Your enum appears to be missing some values! The 1024 value should be Status11, not Status8.

Also note that I added a "None" value for completeness.

L_J · Answer 2 · 2018-06-05T12:05:58.263

1

The bitwise operators can be used for this problem. (1<< i) gives 2 to the power "i". Then bitwise AND (&) with the "value" gives the nonzero number if and only if the corresponding power of two is present in the "value".

public static void GetFlags(int value)
{
    for (int i = 0; i < 20; i++)
    {
        if (((1 << i) & value) > 0)
            Console.WriteLine($"Status {i + 1} is present");
    }
}

edited Jun 05 '18 at 12:05

answered Jun 05 '18 at 07:51

L_J

2,351
10
23
28

3

While this code may answer the question, providing information on *how* and *why* it solves the problem improves its long-term value. – Thomas Flinkow Jun 05 '18 at 09:44

score 0 · Answer 3 · answered Jun 05 '18 at 07:49

0

You can do this with the [Flags] attribute:

[Flags]
enum bla {
  foo = 1,
  bar = 2,
  baz = 4
}

public void Foo() {
  bla flag = (bla)3; // Flags foo and bar
  int andBackToInt = (int)flag; // 3

}

answered Jun 05 '18 at 07:49

JAD

2,035
4
21
35

1

The `Flags` attribute only affects the output of the `ToString` method. It is the use of powers of 2 for the values that allows `enum` values to be combined. – jmcilhinney Jun 05 '18 at 07:51
@jmcilhinney Huh, interesting. TIL. Do you think this answer is worth leaving up then? – JAD Jun 05 '18 at 07:54

score 0 · Answer 4 · answered Jun 05 '18 at 11:34

Thanks all for your quick responses, really appreciate it! :-)

The attribute was new for me. The third party enum has no flags aatribute thats why the Ctype to enum didn't return all values. So i ended up copying all the enums values (via the Object browser it was easy peasy) and creating a local enum WITH the flags attribute set. Now it converts just as i would hope!

Thanks all!

bitwise combination as integer to enum

4 Answers4