How Does the C# [Flags] Enum Attribute Enhance Bitwise Operations and Enumeration Readability?

[Flags] enumerated attributes in [ C#: Understand its role

When defining enumeration in C#, if enumeration represents the set of values ​​rather than a single value, you can use the [Flags] property. This attribute is particularly useful in the enumeration of the use operator.

[Flags] The importance of the attribute

In contrast to the universal misunderstanding, the [Flags] attribute provides a more readable representation form through the method. The enumeration marked with [Flags] will output its value, and the value is displayed in the form of a sign of a comma separation. As shown below:

.ToString() The power value of 2

enum Suits { Spades = 1, Clubs = 2, Diamonds = 4, Hearts = 8 }
[Flags] enum SuitsFlags { Spades = 1, Clubs = 2, Diamonds = 4, Hearts = 8 }

...

var str1 = (Suits.Spades | Suits.Diamonds).ToString(); // "5"
var str2 = (SuitsFlags.Spades | SuitsFlags.Diamonds).ToString(); // "Spades, Diamonds"

It must be emphasized that the [Flags] attribute does not automatically assign the power value of 2 to enumeration. If the value of the value is skipped, the holding of the operation in the position is incorrect, because the default value increases from 0. <确> The correct statement:

<取> Get different values:

To retrieve the different values ​​in the enumeration attributes, you can use multiple methods:

[Flags]
public enum MyColors
{
    Yellow = 1,
    Green = 2,
    Red = 4,
    Blue = 8
}

Use <.> (. Net 4 and higher versions available):

• Use the position operator (before .NET 4):

  .HasFlag()

    if (myProperties.AllowedColors.HasFlag(MyColor.Yellow))
    {
        // Yellow is allowed...
    }

<底> The underlying mechanism

• [Flags] Properties are allowed to operate binary values ​​by operating by bit computing. By using the power value of 2 as an enumeration value, the underlying binary of the value means that it allows efficient and meaningful calculations.

    if ((myProperties.AllowedColors & MyColor.Yellow) == MyColor.Yellow)
    {
        // Yellow is allowed...
    }

  For example, if the attribute AllowEdColors use binary according to the bit or | operational symbols to be Red, Green, and Blue, then AllowedColors will save binary 00001110.

  None = 0 value

  In some enumerations, it contains 0 values ​​(usually named "None"). However, it should be noted that the position and & operations involved in the NONE value always return 0, so it is not suitable for testing specific signs. You can use logical comparison.
  For more information and resources about the [Flags] attributes, its usage and design mode, see the MSDN documentation.

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