Flags enum

Context: Apply the [Flags] attribute to an enum to indicate that its members can be combined using bitwise operations.

[Flags]
public enum Permissions
{
    None   = 0,
    Read   = 1,
    Write  = 2,
    Execute = 4,
    ReadWrite = Read | Write
}

Usage

Permissions perms = Permissions.Read | Permissions.Write;
Console.WriteLine(perms.HasFlag(Permissions.Read)); // True
Console.WriteLine(perms); // Read, Write

// Bitwise operations
perms |= Permissions.Execute; // add flag
perms &= ~Permissions.Write;  // remove flag

Real-world usage example

File access permissions: Use [Flags] enum for FileAccess (Read, Write, ReadWrite) and FileShare (None, Read, Write, ReadWrite, Delete).

Example: In .NET, FileAccess and FileShare are flags enums. Also RegexOptions.

Related sections

• 6.3 Enums
• 6.3.2 Underlying type