See Also: FlagsAttribute Members

System.Object
     System.Attribute
          System.FlagsAttribute

Thread Safety

All public static members of this type are safe for multithreaded operations. No instance members are guaranteed to be thread safe.

Remarks

The FlagsAttribute class provides the consumer of a Enum the information that the enumeration is to be used as a bit-field. Additionally, when formatting a Enum, using the FlagsAttribute causes a value that is a bitwise OR combination of multiple fields to print correctly.

Note:

Bit-fields are generally used for lists of elements that might occur in combination; whereas enumeration constants are generally used for lists of mutually exclusive elements. Therefore, bit-fields are designed to be combined with the bitwise OR operator to generate unnamed values, whereas enumerated constants are not. Languages vary in their usage of bit-fields compared to enumeration constants.

This attribute can only be applied to enumerations.

Example

The following example demonstrates the use of FlagsAttribute on the formatting of a Enum. With this attribute, the Position enumeration is used as a bit-field, and the value 3 (Top | Left) is considered a valid value for the enumeration when formatting. Without this attribute, the enumeration Color is not used as a bit-field, and the value 3 (Red | Blue) is not considered a valid value for the enumeration when formatting.

C# Example

using System;
[FlagsAttribute()] 
public enum Position { 

  Top = 0x1, 
  Left = 0x2, 
  Bottom = 0x4, 
  Right = 0x8 
} 

//enum Color declared without FlagsAttribute 
public enum Color { 

  Red = 0x1, 
  Blue = 0x2, 
  Yellow = 0x4 
} 

public class enumFormat { 

  public static void Main() { 

    Position p = Position.Top | Position.Left; 
    Console.WriteLine("Position: {0}", p); 
    Color c = Color.Red | Color.Blue; 
    Console.WriteLine("Color: {0}", c); 
  } 
} 
      

The output is

Position: Top, Left
Color: 3

Requirements

Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0