C# Academy · Lesson

Flags Enums and Bitwise Combinations

Combine enum values with the Flags attribute.

Lesson 2 of 413 steps

Flags Enums and Bitwise Combinations is a free C# Academy lesson on CoddyKit. This is lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the C# Academy learning path, and your progress syncs across the web and the CoddyKit app. The C# Academy course includes 4 lessons in total.

Flags Enums

A flags enum represents a combination of options. Mark it with the [Flags] attribute and give each member a distinct power of two.

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Write;
        Console.WriteLine(a);
    }
}

Powers of Two

Each flag must occupy a unique bit: 1, 2, 4, 8, 16. This lets values combine without overlap.

using System;

[Flags]
enum Perm { Read = 1, Write = 2, Delete = 4, Share = 8 }
class Program {
    static void Main() {
        Console.WriteLine((int)Perm.Share);
    }
}

Combining with OR

Use bitwise OR (|) to combine flags into one value.

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Execute;
        Console.WriteLine((int)a);
    }
}

Checking with HasFlag

HasFlag tests whether a combined value contains a specific flag.

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Write;
        Console.WriteLine(a.HasFlag(Access.Write));
        Console.WriteLine(a.HasFlag(Access.Execute));
    }
}

Checking with Bitwise AND

You can also test a flag with & and compare to non-zero, which is fast and explicit.

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Write;
        bool canWrite = (a & Access.Write) != 0;
        Console.WriteLine(canWrite);
    }
}

Removing a Flag

Clear a flag with AND of the complement: a &= ~Access.Write.

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Write;
        a &= ~Access.Write;
        Console.WriteLine(a);
    }
}

Adding a Flag

Add a flag by OR-ing it in. If it is already present, nothing changes.

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read;
        a |= Access.Execute;
        Console.WriteLine(a);
    }
}

Toggling a Flag

XOR (^) flips a flag on or off in one step.

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2 }
class Program {
    static void Main() {
        Access a = Access.Read;
        a ^= Access.Write;
        Console.WriteLine(a);
        a ^= Access.Write;
        Console.WriteLine(a);
    }
}

Why [Flags] Matters

The [Flags] attribute changes ToString to print combined names instead of a single number.

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4 }
class Program {
    static void Main() {
        Access a = Access.Read | Access.Execute;
        Console.WriteLine(a);
    }
}

Defining Combined Members

You can define convenience members that are combinations, like All.

using System;

[Flags]
enum Access { None = 0, Read = 1, Write = 2, Execute = 4, All = Read | Write | Execute }
class Program {
    static void Main() {
        Console.WriteLine((int)Access.All);
    }
}

Flags in Practice

Flags model permissions, feature toggles, and option sets compactly in a single integer.

using System;

[Flags]
enum Feature { None = 0, Dark = 1, Beta = 2, Sync = 4 }
class Program {
    static void Main() {
        Feature f = Feature.Dark | Feature.Sync;
        Console.WriteLine(f.HasFlag(Feature.Beta));
    }
}

Quick Check

Test your understanding of flags enums.

Answer it in the interactive lesson

Recap

A [Flags] enum gives each member a unique power of two, so flags combine with | and are tested with HasFlag or &. You add with |=, remove with &= ~, and toggle with ^=.

The attribute makes ToString print combined names, and you can define convenience members like All.

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Combine enum values with the Flags attribute. You practise C# Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

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