Smart Enum

NuGet: Ardalis.SmartEnum

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Smart Enum

An implementation of a type-safe object-oriented alternative to C# enum.

Contributors

Thanks to Scott Depouw and Antão Almada for help with this project!

Install

The framework is provided as a set of NuGet packages.

To install the minimum requirements:

Install-Package Ardalis.SmartEnum

To install support for serialization, select the lines that apply:

Install-Package Ardalis.SmartEnum.AutoFixture
Install-Package Ardalis.SmartEnum.JsonNet
Install-Package Ardalis.SmartEnum.Utf8Json
Install-Package Ardalis.SmartEnum.MessagePack
Install-Package Ardalis.SmartEnum.ProtoBufNet

Usage

Define your smart enum by inheriting from SmartEnum<TEnum> where TEnum is the type you're declaring. For example:

using Ardalis.SmartEnum;

public sealed class TestEnum : SmartEnum<TestEnum>
{
    public static readonly TestEnum One = new TestEnum(nameof(One), 1);
    public static readonly TestEnum Two = new TestEnum(nameof(Two), 2);
    public static readonly TestEnum Three = new TestEnum(nameof(Three), 3);

    private TestEnum(string name, int value) : base(name, value)
    {
    }
}

The default value type is int but it can be set using the second generic argument TValue. The string alias can also be set explicitly, where spaces are allowed.

using Ardalis.SmartEnum;

public sealed class TestEnum : SmartEnum<TestEnum, ushort>
{
    public static readonly TestEnum One = new TestEnum("A string!", 1);
    public static readonly TestEnum Two = new TestEnum("Another string!", 2);
    public static readonly TestEnum Three = new TestEnum("Yet another string!", 3);

    private TestEnum(string name, ushort value) : base(name, value)
    {
    }
}

Just like regular enum, more than one string can be assigned to the same value but only one value can be assigned to a string:

using Ardalis.SmartEnum;

public sealed class TestEnum : SmartEnum<TestEnum>
{
    public static readonly TestEnum One = new TestEnum(nameof(One), 1);
    public static readonly TestEnum Two = new TestEnum(nameof(Two), 2);
    public static readonly TestEnum Three = new TestEnum(nameof(Three), 3);
    public static readonly TestEnum AnotherThree = new TestEnum(nameof(AnotherThree), 3);
    // public static TestEnum Three = new TestEnum(nameof(Three), 4); -> throws exception

    private TestEnum(string name, int value) : base(name, value)
    {
    }
}

In this case, TestEnum.FromValue(3) will return the first instance found, either TestEnum.Three or TestEnum.AnotherThree. No order should be assumed.

The Value content is used when comparing two smart enums, while Name is ignored:

TestEnum.One.Equals(TestEnum.One); // returns true
TestEnum.One.Equals(TestEnum.Three); // returns false
TestEnum.Three.Equals(TestEnum.AnotherThree); // returns true

Inheritance can be used to add "behavior" to a smart enum.

This example adds a BonusSize property, avoiding the use of the switch typically used with regular enums:

using Ardalis.SmartEnum;

public abstract class EmployeeType : SmartEnum<EmployeeType>
{
    public static readonly EmployeeType Manager = new ManagerType();
    public static readonly EmployeeType Assistant = new AssistantType();

    private EmployeeType(string name, int value) : base(name, value)
    {
    }

    public abstract decimal BonusSize { get; }

    private sealed class ManagerType : EmployeeType
    {
        public ManagerType() : base("Manager", 1) {}

        public override decimal BonusSize => 10_000m;
    }

    private sealed class AssistantType : EmployeeType
    {
        public AssistantType() : base("Assistant", 2) {}

        public override decimal BonusSize => 1_000m;
    }
}

This other example implements a state machine. The method CanTransitionTo() returns true if it's allowed to transition from current state to next; otherwise returns false.

using Ardalis.SmartEnum;

public abstract class ReservationStatus : SmartEnum<ReservationStatus>
{
    public static readonly ReservationStatus New = new NewStatus();
    public static readonly ReservationStatus Accepted = new AcceptedStatus();
    public static readonly ReservationStatus Paid = new PaidStatus();
    public static readonly ReservationStatus Cancelled = new CancelledStatus();

    private ReservationStatus(string name, int value) : base(name, value) 
    {
    }

    public abstract bool CanTransitionTo(ReservationStatus next);

    private sealed class NewStatus: ReservationStatus
    {
        public NewStatus() : base("New", 0)
        {
        }

        public override bool CanTransitionTo(ReservationStatus next) =>
            next == ReservationStatus.Accepted || next == ReservationStatus.Cancelled;
    }

    private sealed class AcceptedStatus: ReservationStatus
    {
        public AcceptedStatus() : base("Accepted", 1)
        {
        }

        public override bool CanTransitionTo(ReservationStatus next) =>
            next == ReservationStatus.Paid || next == ReservationStatus.Cancelled;
    }

    private sealed class PaidStatus: ReservationStatus
    {
        public PaidStatus() : base("Paid", 2)
        {
        }

        public override bool CanTransitionTo(ReservationStatus next) =>
            next == ReservationStatus.Cancelled;
    }

    private sealed class CancelledStatus: ReservationStatus
    {
        public CancelledStatus() : base("Cancelled", 3)
        {
        }

        public override bool CanTransitionTo(ReservationStatus next) =>
            false;
    }
}

List

You can list all of the available options using the enum's static List property:

foreach (var option in TestEnum.List)
    Console.WriteLine(option.Name);

List returns an IReadOnlyCollection so you can use the Count property to efficiently get the number of available options.

var count = TestEnum.List.Count;

FromName()

Access an instance of an enum by matching a string to its Name property:

var myEnum = TestEnum.FromName("One");

Exception SmartEnumNotFoundException is thrown when name is not found. Alternatively, you can use TryFromName that returns false when name is not found:

if (TestEnum.TryFromName("One", out var myEnum))
{
    // use myEnum here
}

Both methods have a ignoreCase parameter (the default is case sensitive).

FromValue()

Access an instance of an enum by matching its value:

var myEnum = TestEnum.FromValue(1);

Exception SmartEnumNotFoundException is thrown when value is not found. Alternatively, you can use TryFromValue that returns false when value is not found:

if (TestEnum.TryFromValue(1, out var myEnum))
{
    // use myEnum here
}

ToString()

Display an enum using the ToString() override:

Console.WriteLine(TestEnum.One); // One

Switch

Given an instance of a TestEnum, switch depending on value:

switch(testEnumVar.Name)
{
    case nameof(TestEnum.One):
        ...
        break;
    case nameof(TestEnum.Two):
        ...
        break;
    case nameof(TestEnum.Three):
        ...
        break;
    default:
        ...
        break;
}

Using pattern matching:

switch(testEnumVar)
{
    case null:
        ...
        break;
    case var e when e.Equals(TestEnum.One):
        ...
        break;
    case var e when e.Equals(TestEnum.Two):
        ...
        break;
    case var e when e.Equals(TestEnum.Three):
        ...
        break;
    default:
        ...
        break;
}

Because of the limitations of pattern matching SmartEnum also provides a fluent interface to help create clean code:

testEnumVar
    .When(TestEnum.One).Then(() => ... )
    .When(TestEnum.Two).Then(() => ... )
    .When(TestEnum.Three).Then(() => ... )
    .Default( ... );

N.B. For performance critical code the fluent interface carries some overhead that you may wish to avoid. See the available benchmarks code for your use case.

SmartFlagEnum

Support has been added for a Flag functionality.
This feature is similar to the behaviour seen when applying the [Flag] attribute to Enums in the .NET Framework All methods available on the SmartFlagEnum class return an IEnumerable<SmartFlagEnum> with one or more values depending on the value provided/method called. Some Functionality is shared with the original SmartEnum class, listed below are the variations.

Setting SmartFlagEnum Values

When setting the values for a SmartFlagEnum It is imperative to provide values as powers of two. If at least one value is not set as power of two or two or more power of two values are provided inconsecutively (eg: 1, 2, no four!, 8) a SmartFlagEnumDoesNotContainPowerOfTwoValuesException will be thrown.

public class SmartFlagTestEnum : SmartFlagEnum<SmartFlagTestEnum>
    {
        public static readonly SmartFlagTestEnum None = new SmartFlagTestEnum(nameof(None), 0);
        public static readonly SmartFlagTestEnum Card = new SmartFlagTestEnum(nameof(Card), 1);
        public static readonly SmartFlagTestEnum Cash = new SmartFlagTestEnum(nameof(Cash), 2);
        public static readonly SmartFlagTestEnum Bpay = new SmartFlagTestEnum(nameof(Bpay), 4);
        public static readonly SmartFlagTestEnum Paypal = new SmartFlagTestEnum(nameof(Paypal), 8);
        public static readonly SmartFlagTestEnum BankTransfer = new SmartFlagTestEnum(nameof(BankTransfer), 16);

        public SmartFlagTestEnum(string name, int value) : base(name, value)
        {
        }
    }

This behaviour can be disabled by applying the AllowUnsafeFlagEnumValuesAttribute to the smart enum class. Note: If power of two values are not provided the SmarFlagEnum will not behave as expected!

[AllowUnsafeFlagEnumValues]
public class SmartFlagTestEnum : SmartFlagEnum<SmartFlagTestEnum>
    {
        public static readonly SmartFlagTestEnum None = new SmartFlagTestEnum(nameof(None), 0);
        public static readonly SmartFlagTestEnum Card = new SmartFlagTestEnum(nameof(Card), 1);
        public static readonly SmartFlagTestEnum Cash = new SmartFlagTestEnum(nameof(Cash), 2);
        public static readonly SmartFlagTestEnum Bpay = new SmartFlagTestEnum(nameof(Bpay), 4);
        public static readonly SmartFlagTestEnum Paypal = new SmartFlagTestEnum(nameof(Paypal), 8);
        public static readonly SmartFlagTestEnum BankTransfer = new SmartFlagTestEnum(nameof(BankTransfer), 16);

        public SmartFlagTestEnum(string name, int value) : base(name, value)
        {
        }
    }

Combination values can be provided explicitly and will be returned in place of the multiple flag values that would have been returned from the FromValue() method.

public class SmartFlagTestEnum : SmartFlagEnum<SmartFlagTestEnum>
    {
        public static readonly SmartFlagTestEnum None = new SmartFlagTestEnum(nameof(None), 0);
        public static readonly SmartFlagTestEnum Card = new SmartFlagTestEnum(nameof(Card), 1);
        public static readonly SmartFlagTestEnum Cash = new SmartFlagTestEnum(nameof(Cash), 2);
        public static readonly SmartFlagTestEnum CardAndCash = new SmartFlagTestEnum(nameof(CardAndCash), 3); -- Explicit `Combination` value
        public static readonly SmartFlagTestEnum Bpay = new SmartFlagTestEnum(nameof(Bpay), 4);
        public static readonly SmartFlagTestEnum Paypal = new SmartFlagTestEnum(nameof(Paypal), 8);
        public static readonly SmartFlagTestEnum BankTransfer = new SmartFlagTestEnum(nameof(BankTransfer), 16);

        public SmartFlagTestEnum(string name, int value) : base(name, value)
        {
        }
    }

These explicit values can be provided above the highest allowable flag value without consequence, however attempting to access a value that is higher than the maximum flag value that has not explicitly been provided (for example 4) will cause a SmartEnumNotFoundException to be thrown.

public class SmartFlagTestEnum : SmartFlagEnum<SmartFlagTestEnum>
    {
        public static readonly SmartFlagTestEnum None = new SmartFlagTestEnum(nameof(None), 0);
        public static readonly SmartFlagTestEnum Card = new SmartFlagTestEnum(nameof(Card), 1);
        public static readonly SmartFlagTestEnum Cash = new SmartFlagTestEnum(nameof(Cash), 2);
        public static readonly SmartFlagTestEnum AfterPay = new SmartFlagTestEnum(nameof(AfterPay), 5);

        public SmartFlagTestEnum(string name, int value) : base(name, value)
        {
        }
    }
    
    var myFlagEnums = FromValue(3) -- Works!
    -and-
    var myFlagEnums = FromValue(5) -- Works!
    -but-
    Var myFlagEnums = FromValue(4) -- will throw an exception :(

A Negative One (-1) value may be provided as an All value. When a value of -1 is passed into any of the FromValue() methods an IEnumerable containing all values (excluding 0) will be returned.
If an explicit Combination value exists with a value of -1 this will be returned instead.

public class SmartFlagTestEnum : SmartFlagEnum<SmartFlagTestEnum>
    {
        public static readonly SmartFlagTestEnum All = new SmartFlagTestEnum(nameof(All), -1);
        public static readonly SmartFlagTestEnum None = new SmartFlagTestEnum(nameof(None), 0);
        public static readonly SmartFlagTestEnum Card = new SmartFlagTestEnum(nameof(Card), 1);
        public static readonly SmartFlagTestEnum Cash = new SmartFlagTestEnum(nameof(Cash), 2);
        public static readonly SmartFlagTestEnum Bpay = new SmartFlagTestEnum(nameof(Bpay), 4);
        public static readonly SmartFlagTestEnum Paypal = new SmartFlagTestEnum(nameof(Paypal), 8);
        public static readonly SmartFlagTestEnum BankTransfer = new SmartFlagTestEnum(nameof(BankTransfer), 16);

        public SmartFlagTestEnum(string name, int value) : base(name, value)
        {
        }
    }

Usage - (SmartFlagEnum)

public abstract class EmployeeType : SmartFlagEnum<EmployeeType>
    {
        public static readonly EmployeeType Director = new DirectorType();
        public static readonly EmployeeType Manager = new ManagerType();
        public static readonly EmployeeType Assistant = new AssistantType();

        private EmployeeType(string name, int value) : base(name, value)
        {
        }

        public abstract decimal BonusSize { get; }

        private sealed class DirectorType : EmployeeType
        {
            public DirectorType() : base("Director", 1) { }

            public override decimal BonusSize => 100_000m;
        }

        private sealed class ManagerType : EmployeeType
        {
            public ManagerType() : base("Manager", 2) { }

            public override decimal BonusSize => 10_000m;
        }

        private sealed class AssistantType : EmployeeType
        {
            public AssistantType() : base("Assistant", 4) { }

            public override decimal BonusSize => 1_000m;
        }
    }

    public class SmartFlagEnumUsageExample
    {
        public void UseSmartFlagEnumOne()
        {
            var result = EmployeeType.FromValue(3).ToList();
            
            var outputString = "";
            foreach (var employeeType in result)
            {
                outputString += $"{employeeType.Name} earns ${employeeType.BonusSize} bonus this year.\n";
            }
            
                => "Director earns $100000 bonus this year.\n"
                   "Manager earns $10000 bonus this year.\n"
        }
         
        public void UseSmartFlagEnumTwo()
        {
            EmployeeType.FromValueToString(-1)
                => "Director, Manager, Assistant"
        }
            
        public void UseSmartFlagEnumTwo()
        {
            EmployeeType.FromValueToString(EmployeeType.Assistant | EmployeeType.Director)
                => "Director, Assistant"
        }
    }

FromName()

Access an IEnumerable of enum instances by matching a string containing one or more enum names seperated by commas to its Names property:

var myFlagEnums = TestFlagEnum.FromName("One, Two");

Exception SmartEnumNotFoundException is thrown when no names are found. Alternatively, you can use TryFromName that returns false when no names are found:

if (TestFlagEnum.TryFromName("One, Two", out var myFlagEnums))
{
    // use myFlagEnums here
}

Both methods have a ignoreCase parameter (the default is case sensitive).

FromValue()

Access an IEnumerable of enum instances by matching a value:

var myFlagEnums = TestFlagEnum.FromValue(3);

Exception SmartEnumNotFoundException is thrown when no values are found. Alternatively, you can use TryFromValue that returns false when values are not found:

if (TestFlagEnum.TryFromValue(3, out var myFlagEnums))
{
    // use myFlagEnums here
}

Note: Negative values other than (-1) passed into this method will cause a NegativeValueArgumentException to be thrown, this behaviour can be disabled by applying the AllowNegativeInput attribute to the desired SmartFlagEnum class.

[AllowNegativeInput]
public class SmartFlagTestEnum : SmartFlagEnum<SmartFlagTestEnum>
    {
        public static readonly SmartFlagTestEnum None = new SmartFlagTestEnum(nameof(None), 0);
        public static readonly SmartFlagTestEnum Card = new SmartFlagTestEnum(nameof(Card), 1);

        public SmartFlagTestEnum(string name, int value) : base(name, value)
        {
        }
    }

Note: FromValue() will accept any input that can be succesfully parsed as an integer. If an invalid value is supplied it will throw an InvalidFlagEnumValueParseException.

FromValueToString()

Return a string representation of a series of enum instances name's:

var myFlagEnumString = TestFlagEnum.FromValueToString(3);

Exception SmartEnumNotFoundException is thrown when no values are found. Alternatively, you can use TryFromValueToString that returns false when values are not found:

if (TestFlagEnum.TryFromValueToString(3, out var myFlagEnumsAsString))
{
    // use myFlagEnumsAsString here
}

Note: Negative values other than (-1) passed into this method will cause a NegativeValueArgumentException to be thrown, this behaviour can be disabled by applying the AllowNegativeInput attribute to the desired SmartFlagEnum class.

BitWiseOrOperator

The FromValue() methods allow the Or ( | ) operator to be used to add enum values together and provide multiple values at once.

var myFlagEnums = TestFlagEnum.FromValue(TestFlagEnum.One | TestFlagEnum.Two);

This will only work where the type of the SmartFlagEnum has been specified as Int32 or else can be explicitly cast as an Int32.

var myFlagEnums = TestFlagEnumDecimal.FromValue((int)TestFlagEnum.One | (int)TestFlagEnum.Two);

Persisting with EF Core 2.1 or higher

EF Core 2.1 introduced value conversions which can be used to map SmartEnum types to simple database types. For example, given an entity named Policy with a property PolicyStatus that is a SmartEnum, you could use the following code to persist just the value to the database:

protected override void OnModelCreating(ModelBuilder builder)
{
    base.OnModelCreating(builder);

    builder.Entity<Policy>()
        .Property(p => p.PolicyStatus)
        .HasConversion(
            p => p.Value,
            p => PolicyStatus.FromValue(p));
}

AutoFixture support

New instance of a SmartEnum should not be created. Instead, references to the existing ones should always be used. AutoFixture by default doesn't know how to do this. The Ardalis.SmartEnum.AutoFixture package includes a specimen builder for SmartEnum. Simply add the customization to the IFixture builder:

var fixture = new Fixture()
    .Customize(new SmartEnumCustomization());

var smartEnum = fixture.Create<TestEnum>();

Json.NET support

When serializing a SmartEnum to JSON, only one of the properties (Value or Name) should be used. Json.NET by default doesn't know how to do this. The Ardalis.SmartEnum.JsonNet package includes a couple of converters to achieve this. Simply use the attribute JsonConverterAttribute to assign one of the converters to the SmartEnum to be de/serialized:

public class TestClass
{
    [JsonConverter(typeof(SmartEnumNameConverter<int>))]
    public TestEnum Property { get; set; }
}

uses the Name:

{
  "Property": "One"
}

While this:

public class TestClass
{
    [JsonConverter(typeof(SmartEnumValueConverter<int>))]
    public TestEnum Property { get; set; }
}

uses the Value:

{
  "Property": 1
}

Note: The SmartFlagEnum works identically to the SmartEnum when being Serialized and Deserialized.

Name		Name	Last commit message	Last commit date
Latest commit History 72 Commits
.github		.github
benchmarks/SmartEnum.Benchmarks		benchmarks/SmartEnum.Benchmarks
src		src
test		test
.gitignore		.gitignore
Directory.Build.props		Directory.Build.props
LICENSE		LICENSE
README.md		README.md
SmartEnum.sln		SmartEnum.sln
azure-pipelines.yml		azure-pipelines.yml
nuget.txt		nuget.txt

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Smart Enum

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Install

Usage

List

FromName()

FromValue()

ToString()

Switch

SmartFlagEnum

Setting SmartFlagEnum Values

Usage - (SmartFlagEnum)

FromName()

FromValue()

FromValueToString()

BitWiseOrOperator

Persisting with EF Core 2.1 or higher

AutoFixture support

Json.NET support

References

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AFM-Horizon/SmartEnum

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Give a Star! ⭐

Smart Enum

Contributors

Install

Usage

List

FromName()

FromValue()

ToString()

Switch

SmartFlagEnum

Setting SmartFlagEnum Values

Usage - (SmartFlagEnum)

FromName()

FromValue()

FromValueToString()

BitWiseOrOperator

Persisting with EF Core 2.1 or higher

AutoFixture support

Json.NET support

References

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