Java vs. C# Enums: How Do Extension Methods Bridge the Gap?

Getting Started Guide to Enumerations in Java and C#

Developers moving from Java to C# may find that C#'s enumerations seem to be simpler than Java's implementation. Let’s explore the differences between Java and C# enumerations and how to overcome them.

Main Differences

• Method support: Java enums support defining methods, which C# enums traditionally do not.

Use extension methods to overcome differences

In C#, you can create extension methods for enumerations to add methods such as surfaceGravity() and surfaceWeight(). For example:

using System;

class PlanetAttr : Attribute
{
    internal PlanetAttr(double mass, double radius)
    {
        this.Mass = mass;
        this.Radius = radius;
    }
    public double Mass { get; private set; }
    public double Radius { get; private set; }
}

public static class Planets
{
    public static double GetSurfaceGravity(this Planet p)
    {
        PlanetAttr attr = GetAttr(p);
        return G * attr.Mass / (attr.Radius * attr.Radius);
    }

    public static double G = 6.67300E-11;

    private static PlanetAttr GetAttr(Planet p)
    {
        return (PlanetAttr)Attribute.GetCustomAttribute(ForValue(p), typeof(PlanetAttr));
    }

    private static MemberInfo ForValue(Planet p)
    {
        return typeof(Planet).GetField(Enum.GetName(typeof(Planet), p));
    }
}

public enum Planet
{
    [PlanetAttr(3.303e+23, 2.4397e6)]  MERCURY,
    // ... other planets
}

With this code, you can access the Planet methods of each GetSurfaceGravity() enumeration value.

Summary

While Java enums offer more built-in functionality, C# enums offer greater flexibility through extension methods. By implementing method extensions, you can replicate the functionality of a Java enumeration and customize the enumeration to your specific needs.

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