C# vs Java Enum (for those new to C#)

java

enum-engineering

reflection

best-practices

byAlex Kataev·Nov 30, 2024

In C#, enums are basically named integers, ideal for value enumeration:

enum Colour { Red, Green, Blue }; // Some primary hues for you!

Meanwhile, Java enums are more muscular allowing methods, fields, and exhibiting dynamic class-like capabilities:

public enum Colour {
    RED, GREEN, BLUE;

    private static final Map<String, Colour> BY_LABEL = new HashMap<>();

    static {
        for (Colour e : values()) { // Java enum pumping iron 💪
            BY_LABEL.put(e.name(), e);
        }
    }

    public static Colour valueOfLabel(String label) { 
        return BY_LABEL.get(label); // Java enum has got your label's back!
    }
}

But, fear not. To squeeze in extra powers into C# enums similar to Java, we can rely on extension methods:

public enum Colour { Red, Green, Blue };

public static class ColourExtensions {
    public static string ToHex(this Colour c) {
        switch(c) { // Switching colours like a chameleon 🦎
            case Colour.Red: return "#FF0000";
            case Colour.Green: return "#00FF00";
            case Colour.Blue: return "#0000FF";
            default: throw new ArgumentOutOfRangeException(nameof(c), "Unknown colour, did you invent a new one?");
        }
    }
}

C# Enum X-ray: Custom attributes and reflection

To over-boost your C# enums akin to the Java counterparts, custom attributes and reflection make a brilliant tag team:

public enum Colour {
    [HexValue("#FF0000")] Red, // As red as a blushing apple 🍎
    [HexValue("#00FF00")] Green, // As green as a fresh cucumber 🥒
    [HexValue("#0000FF")] Blue // As blue as a clear sky 🌌
}

public class HexValueAttribute : Attribute {
    public string Value { get; }

    public HexValueAttribute(string value) {
        Value = value;
    }
}

// To access these nifty custom attributes:
var hexValue = Attribute.GetCustomAttribute(typeof(Colour), typeof(HexValueAttribute)) as HexValueAttribute;
var colourHex = hexValue?.Value; // Don't forget null checks, or you'll be in a null of a mess!

Creating pseudo-Java enums in C#

In C#, enums fall short of having methods or properties compared to their beefy Java cousins. But, mirroring these using immutable classes with static readonly instances is a smart workaround:

public class ColourClass {
    public static readonly ColourClass Red = new ColourClass("#FF0000"); // Hot and fierce!
    public static readonly ColourClass Green = new ColourClass("#00FF00"); // Cool and composed!
    public static readonly ColourClass Blue = new ColourClass("#0000FF"); // Deep and mysterious!

    public string HexValue { get; private set; }
    private ColourClass(string hex) { // Don't worry, this class won't hex you! 😄
        HexValue = hex;
    }
}

This pattern impersonates Java enums, giving a class-like feel to enumerated values.

C# Enum Detour: The Dictionary approach

If you want to skirt around custom attributes and salvage simplicity, a Dictionary might be what you need:

Dictionary<Colour, string> colourHexValues = new Dictionary<Colour, string> {
    {Colour.Red, "#FF0000"}, // Who let the red out? Woof, woof! 🐾
    {Colour.Green, "#00FF00"}, // Green means go... forward! 🟢
    {Colour.Blue, "#0000FF"} // Don't be blue, you're doing great! 💙
};

Comparing enum values: A fair game in both C# and Java

In Java, enum values are best compared using == as they're unique singletons:

if(day == Day.MONDAY) { /* In case of Monday blues, insert motivational quote here! */ }

In C#, the game is the same, keeping in mind that they're fundamentally integers:

if(colour == Colour.Red) { /* Looks like someone's painting the town red! */ }

Uncovering the enum treasure

Delve deeper with insights from esteemed Jon Skeet's take on C# enums, Codeproject's knowledgeable pieces on advanced enum usage in C#, or the promising enum_ext project on GitHub.

At the end of the day, the key lies in exploring, experimenting, and experiencing!

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