bool isOption2And3Set = (value & FlagsEnum.Option2And3) == FlagsEnum.Option2And3;

Assert.True(isOption2And3Set);

Section 22.5: Add and remove values from flagged enum

This code is to add and remove a value from a flagged enum-instance:

[Flags]

public enum MyEnum

{

Flag1 = 1 << 0, Flag2 = 1 << 1, Flag3 = 1 << 2

}

var value = MyEnum.Flag1;

// set additional value

value |= MyEnum.Flag2; //value is now Flag1, Flag2

value |= MyEnum.Flag3; //value is now Flag1, Flag2, Flag3

// remove flag

value &= ~MyEnum.Flag2; //value is now Flag1, Flag3

Section 22.6: Enum to string and back

public enum DayOfWeek

{

Sunday,

Monday,

Tuesday,

Wednesday,

Thursday,

Friday,

Saturday

}

// Enum to string

string thursday = DayOfWeek.Thursday.ToString(); // "Thursday"

string seventhDay = Enum.GetName(typeof(DayOfWeek), 6); // "Saturday"

string monday = Enum.GetName(typeof(DayOfWeek), DayOfWeek.Monday); // "Monday"

// String to enum (.NET 4.0+ only - see below for alternative syntax for earlier .NET versions)

DayOfWeek tuesday;

Enum.TryParse("Tuesday", out tuesday); // DayOfWeek.Tuesday

DayOfWeek sunday;

bool matchFound1 = Enum.TryParse("SUNDAY", out sunday); // Returns false (case-sensitive match)

DayOfWeek wednesday;

bool matchFound2 = Enum.TryParse("WEDNESDAY", true, out wednesday); // Returns true; DayOfWeek.Wednesday (case-insensitive match)

// String to enum (all .NET versions)

DayOfWeek friday = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), "Friday"); // DayOfWeek.Friday

DayOfWeek caturday = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), "Caturady"); // Thows ArgumentException

// All names of an enum type as strings

string[] weekdays = Enum.GetNames(typeof(DayOfWeek));

Section 22.7: Enums can have unexpected values

Since an enum can be cast to and from its underlying integral type, the value may fall outside the range of values given in the definition of the enum type.

Although the below enum type DaysOfWeek only has 7 defined values, it can still hold any int value.

public enum DaysOfWeek

{

Monday = 1,

Tuesday = 2, Wednesday = 3, Thursday = 4, Friday = 5, Saturday = 6, Sunday = 7

}

DaysOfWeek d = (DaysOfWeek)31;

Console.WriteLine(d); // prints 31

DaysOFWeek s = DaysOfWeek.Sunday; s++; // No error

There is currently no way to define an enum which does not have this behavior.

However, undefined enum values can be detected by using the method Enum.IsDefined. For example,

DaysOfWeek d = (DaysOfWeek)31;

Console.WriteLine(Enum.IsDefined(typeof(DaysOfWeek),d)); // prints False

Section 22.8: Default value for enum == ZERO

The default value for an enum is zero. If an enum does not define an item with a value of zero, its default value will be zero.

public class Program

{

enum EnumExample

{

one = 1, two = 2

}

public void Main()

{

var e = default(EnumExample);

if (e == EnumExample.one) Console.WriteLine("defaults to one");

else

Console.WriteLine("Unknown");

}

}

Example: https://dotnetfiddle.net/l5Rwie

Section 22.9: Adding additional description information to an enum value

In some cases you might want to add an additional description to an enum value, for instance when the enum value itself is less readable than what you might want to display to the user. In such cases you can use the

System.ComponentModel.DescriptionAttribute class.

For example:

public enum PossibleResults

{

[Description("Success")] OK = 1,

[Description("File not found")] FileNotFound = 2, [Description("Access denied")] AccessDenied = 3

}

Now, if you would like to return the description of a specific enum value you can do the following:

public static string GetDescriptionAttribute(PossibleResults result)

{

return ((DescriptionAttribute)Attribute.GetCustomAttribute((result.GetType().GetField(result.ToString())), typeof(DescriptionAttribute))).Description;

}

static void Main(string[] args)

{

PossibleResults result = PossibleResults.FileNotFound; Console.WriteLine(result); // Prints "FileNotFound" Console.WriteLine(GetDescriptionAttribute(result)); // Prints "File not found"

}

This can also be easily transformed to an extension method for all enums:

static class EnumExtensions

{

public static string GetDescription(this Enum enumValue)

{

return ((DescriptionAttribute)Attribute.GetCustomAttribute((enumValue.GetType().GetField(enumValue.ToStrin g())), typeof(DescriptionAttribute))).Description;

}

}

And then easily used like this: Console.WriteLine(result.GetDescription());

Section 22.10: Get all the members values of an enum

enum MyEnum

{

One,

Two,

Three

}

foreach(MyEnum e in Enum.GetValues(typeof(MyEnum)))

Console.WriteLine(e);

This will print:

One

Two

Three

Section 22.11: Bitwise Manipulation using enums

The FlagsAttribute should be used whenever the enumerable represents a collection of flags, rather than a single value. The numeric value assigned to each enum value helps when manipulating enums using bitwise operators.

Example 1 : With [Flags]

[Flags] enum Colors

{

Red=1,

Blue=2,

Green=4,

Yellow=8

}

var color = Colors.Red | Colors.Blue; Console.WriteLine(color.ToString());

prints Red,Blue

Example 2 : Without [Flags]

enum Colors

{

Red=1,

Blue=2,

Green=4,

Yellow=8

}

var color = Colors.Red | Colors.Blue; Console.WriteLine(color.ToString());

prints 3