如何扩展枚举类型？

// 原始枚举
enum Color {
    RED, GREEN, BLUE;
}

// 扩展接口
interface ExtendedColor {
    String getHexCode();
}

// 实现扩展接口
enum ExtendedColorImpl implements ExtendedColor {
    YELLOW("#FFFF00"),
    PURPLE("#800080");

    private final String hexCode;

    ExtendedColorImpl(String hexCode) {
        this.hexCode = hexCode;
    }

    @Override
    public String getHexCode() {
        return hexCode;
    }
}

// 原始枚举
enum Color {
    Red, Green, Blue
}

// 扩展类
public class ExtendedColor : Color {
    public static readonly ExtendedColor Yellow = (ExtendedColor)(int)Color.Red + 1;
    public static readonly ExtendedColor Purple = (ExtendedColor)(int)Color.Red + 2;

    private ExtendedColor(int value) : base(value) { }

    public string GetHexCode() {
        switch (this) {
            case ExtendedColor.Yellow: return "#FFFF00";
            case ExtendedColor.Purple: return "#800080";
            default: throw new ArgumentException();
        }
    }
}

// 原始枚举
enum Color {
    Red = "RED",
    Green = "GREEN",
    Blue = "BLUE"
}

// 扩展枚举
type ExtendedColor = Color | "YELLOW" | "PURPLE";

// 使用扩展枚举
function getColorHex(color: ExtendedColor): string {
    switch (color) {
        case Color.Red: return "#FF0000";
        case Color.Green: return "#00FF00";
        case Color.Blue: return "#0000FF";
        case "YELLOW": return "#FFFF00";
        case "PURPLE": return "#800080";
        default: throw new Error("Unknown color");
    }
}

// 使用字典模拟动态枚举
public class DynamicEnum {
    private static readonly Dictionary<string, int> Values = new Dictionary<string, int> {
        { "Red", 0 },
        { "Green", 1 },
        { "Blue", 2 }
    };

    public static void AddValue(string name, int value) {
        Values[name] = value;
    }

    public static bool TryGetValue(string name, out int value) {
        return Values.TryGetValue(name, out value);
    }
}