Store multiple true values with an enum

Question

I have recently started using enums to more efficiently store information in a database. I was wondering if there is some way to use them to store multiple true values. To elaborate, in a enum such as GenderEnum I would store male as 0, female as 1, OtherUnclear as 3 in the database.

public enum GenderEnum : short
 {
    Male,
    Female,
    OtherUnclear
  }

But what if I wanted to store multiple true values? For race for example somebody could be multiracial. How would I store somebody who was, say, Black and White efficiently in a database?

public enum RaceEnum : short
  {
     White,
     Black,
     Hispanic,
     Asian,
     Native,
     Unclear
  }

you can add one more value to the enum as BlackAndWhite – Vivek Nuna Jul 04 '20 at 10:22 — Vivek Nuna, Jul 04 '20 at 10:22

score 4 · Answer 1 · 2020-07-04T16:26:25.700

You can use the flags attribute that allows bitwise mixing with the logic OR operator and set each values a multiple of 2 using the sequence of binary values after 0 and 1:

[Flags]
public enum EthnicGroup : short
{
   White = 0,
   Black = 1,
   Hispanic = 2,
   Asian = 4,
   Native = 8,
   Unclear = 16
}

You can check if a variable has a flag set using the Enum.HasFlag method.

Example

var somehuman = EthnicGroup.Black | EthnicGroup.Hispanic;

if ( somehuman.HasFlag(EthnicGroup.Asian) ) ...

Resources

What does the [Flags] Enum Attribute mean in C#?

https://www.alanzucconi.com/2015/07/26/enum-flags-and-bitwise-operators

https://learn.microsoft.com/dotnet/api/system.flagsattribute

https://learn.microsoft.com/dotnet/api/system.enum.hasflag

score 4 · Accepted Answer · answered Jul 04 '20 at 10:31

If you want an enumeration type to represent a combination of choices, define enum members for those choices such that an individual choice is a bit field. To indicate that an enumeration type declares bit fields, apply the Flags attribute to it.

Below is a simple example.

[Flags]
public enum Days
{
    None      = 0b_0000_0000,  // 0
    Monday    = 0b_0000_0001,  // 1
    Tuesday   = 0b_0000_0010,  // 2
    Wednesday = 0b_0000_0100,  // 4
    Thursday  = 0b_0000_1000,  // 8
    Friday    = 0b_0001_0000,  // 16
    Saturday  = 0b_0010_0000,  // 32
    Sunday    = 0b_0100_0000,  // 64
    Weekend   = Saturday | Sunday
}

public class FlagsEnumExample
{
    public static void Main()
    {
        Days meetingDays = Days.Monday | Days.Wednesday | Days.Friday;
        Console.WriteLine(meetingDays);
        // Output:
        // Monday, Wednesday, Friday

        Days workingFromHomeDays = Days.Thursday | Days.Friday;
        Console.WriteLine($"Join a meeting by phone on {meetingDays & workingFromHomeDays}");
        // Output:
        // Join a meeting by phone on Friday

        bool isMeetingOnTuesday = (meetingDays & Days.Tuesday) == Days.Tuesday;
        Console.WriteLine($"Is there a meeting on Tuesday: {isMeetingOnTuesday}");
        // Output:
        // Is there a meeting on Tuesday: False

        var a = (Days)37;
        Console.WriteLine(a);
        // Output:
        // Monday, Wednesday, Saturday
    }
}

Reference: https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/enum#enumeration-types-as-bit-flags

Store multiple true values with an enum

2 Answers2