How can C# Enums be Enhanced with Extension Methods and Custom Attributes to Mimic Java Enum Functionality?

C# vs Java Enums: A Comparative Guide

If you're transitioning from Java to C#, you may notice some differences in how enums are implemented. While C# enums appear simpler initially, they offer distinct advantages through extension methods and custom attributes.

Key Differences

• Extension Methods: In C#, you can extend enums with additional functionality, including custom methods and properties. This compensates for the lack of built-in methods like surfaceGravity() and surfaceWeight() in the Java enum implementation.
• Custom Attributes: C# allows you to attach custom attributes to enums, providing a way to store additional metadata. This can be utilized to effectively emulate the fields and methods of Java enums, as demonstrated in the example below.

Example with Extension Methods and Custom Attributes

We can define an enum for planets and add extension methods for GetSurfaceGravity() and GetSurfaceWeight():

public enum Planet
{
    [PlanetAttr(3.303e+23, 2.4397e6)]  MERCURY,
    [PlanetAttr(4.869e+24, 6.0518e6)]  VENUS,
    [PlanetAttr(5.976e+24, 6.37814e6)] EARTH,
    ...
}

public static class Planets
{
    public static double GetSurfaceGravity(this Planet p)
    {
        PlanetAttr attr = GetAttr(p);
        ...
    }
    ...
}

We can then use these extension methods to perform calculations similarly to the Java example:

double earthWeight = Double.parseDouble(args[0]);
double mass = earthWeight/Planet.EARTH.GetSurfaceGravity();
for (Planet p : Planet.values())
    System.out.printf("Your weight on %s is %f%n", p, p.GetSurfaceWeight(mass));

This example demonstrates how to create a C# enum with enhanced functionality that closely resembles the Java implementation.

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