Can Multiple Enum Values Share the Same Underlying Value in C#?

Unveiling the Mystery of Non-Unique Enum Values

While attempting to obfuscate index positions in an EDI file, a surprising discovery was made: the ability to assign multiple values to the same enum. This seemingly unusual behavior has raised questions about the logic behind it and its potential implications.

Enums, as it turns out, are essentially structs that inherit from System.Enum. Behind the scenes, enum values are defined as constants. For instance, the following enum definition:

public enum Color
{
    Red = 1,
    Blue = 1,
    Green = 1
}

is effectively equivalent to the following pseudo-code:

public struct Color : System.Enum
{
    public const int Red = 1;
    public const int Blue = 1;
    public const int Green = 1;
}

This reveals that the enum is essentially a collection of constants with the same underlying value. While in C# it's prohibited to define a struct with an explicit base class, this is precisely what an enum definition translates to.

As a result, there is no inherent conflict in having multiple constants with the same value in an enum type. However, this can lead to ambiguity when converting to the enum. For example:

Color color1 = (Color)1; // Returns Red
Color color2 = (Color)Enum.Parse(typeof(Color), "1"); // Also returns Red

The value assigned to both color1 and color2 is technically not Red but 1. Yet, when printed, it appears as Red.

Additionally, comparing non-unique enum values may yield puzzling results:

bool b = Color.Red == Color.Green; // True (Red is Green??)

While the comparison may seem logically incorrect, it is a consequence of the underlying values being equal.

Ultimately, the use of non-unique enum values is a matter of judgment. It's important to weigh the risks and benefits carefully before utilizing this approach.

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