In this article, Khalid Abuhakmeh details how to create generic helper methods in C# for working with enums, including code samples and best practices on enforcing type constraints.

Article Summary

Author Khalid Abuhakmeh presents a practical approach to creating reusable, type-safe generic methods for handling enums in .NET applications. Drawing from personal experience, he notes that developers often build similar helpers to retrieve metadata (like descriptions) from enums using reflection.

Key Points

  • Common Need: .NET developers frequently require utility methods to read metadata from enums, which may have attributes that describe each value (such as [Description("...")]).
  • Historic Limitation: Earlier versions of .NET/C# had difficulties combining generics and enums because generic constraints couldn’t restrict types to “enums only.” This made the implementation less type-safe.
  • Modern Solution: Recent language improvements allow developers to constrain generic methods with where TEnum: struct, Enum, ensuring only enums are allowed and that they are non-nullable.

Sample Code Overview

Abuhakmeh shares code that leverages generics and reflection to get descriptions for all enum values or a single value:

Example Enum

public enum Groceries {
    [Description("Apples, Oranges, Bananas")] Fruit,
    [Description("Spinach, Kale, Broccoli, Cabbage")] Vegetables,
    [Description("Cheese, Milk, Yogurt")] Dairy,
    [Description("Chicken, Beef, Pork, Lamb, Turkey")] Meat,
    [Description("Anything not listed above")] Other
}

Helper Class

public static class Enums {
    public static IEnumerable<(TEnum Value, string Description)> GetDescriptions<TEnum>() where TEnum : struct, Enum {
        var values = Enum.GetValues<TEnum>();
        foreach (var value in values) {
            yield return GetDescription(value);
        }
    }
    public static (TEnum Value, string Description) GetDescription<TEnum>(TEnum value) where TEnum : struct, Enum {
        var type = typeof(TEnum);
        var name = value.ToString();
        var info = type.GetMember(name)[0];
        var description = info.GetCustomAttribute<DescriptionAttribute>() is { } attr ? attr.Description : name;
        return (value, description);
    }
}

Explanation of Constraints

  • The where TEnum : struct, Enum constraint ensures that only non-nullable enum types are accepted, making the helper both flexible (works with any enum) and safe (prevents misuse with inappropriate types).
  • Using reflection, the helper reads the DescriptionAttribute if present, or defaults to the enum name.

Use Cases

  • Web Applications: These methods are particularly useful when building lists for UI elements (e.g., dropdown selections) in ASP.NET or similar frameworks.
  • General Reusability: The approach saves time and reduces code repetition by providing a standardized method to extract enum metadata across a solution.

Conclusion

The article demonstrates the power and convenience of modern C# generics combined with enum constraints. Developers can now create robust helpers that work on any enum, making code more maintainable and type-safe. These techniques are particularly advantageous for scenarios requiring display-friendly enum values, such as web applications.

This post appeared first on Khalid Abuhakmeh’s Blog. Read the entire article here