有没有一种替代这种奇怪的循环模板模式的方法?

这不是很优雅,但像这样的东西可能会起作用:

public class DocketType : Enumeration<DocketType, int, string>
{
    public static readonly DocketType Withdrawal =
        new DocketType(2, "Withdrawal");

    public static readonly DocketType Installation =
        new DocketType(3, "Installation");

    private DocketType(int docketTypeId, string description)
        : base(docketTypeId, description) { }
}

public abstract class Enumeration<TEnum, TId, TDescription> : IComparable
    where TEnum : Enumeration<TEnum, TId, TDescription>
{
    private static readonly Dictionary<TId, TEnum> _cache;

    static Enumeration()
    {
        Type t = typeof(TEnum);
        _cache = t.GetFields(BindingFlags.Public | BindingFlags.Static)
                  .Where(f => f.FieldType == t)
                  .Select(f => (TEnum)f.GetValue(null))
                  .ToDictionary(e => e.Id, e => e);
    }

    public static TEnum Resolve(TId id)
    {
        return _cache[id];
    }

    public TId Id { get; private set; }
    public TDescription Description { get; private set; }

    protected Enumeration(TId id, TDescription description)
    {
        Id = id;
        Description = description;
    }

    // IComparable
    public int CompareTo(object obj)
    {
        // TODO
        throw new NotImplementedException();
    }
}

您需要将静态字段推入一个类中,该类将静态实例作为实例字段。这样,就可以通过一个静态成员访问枚举,该静态成员会立即引用所有枚举成员。

// The Collection of values to be enumerated
public class DocketEnum : EnumarationCollection<DocketType, int, string>
{
        // Values are fields on a statically instanced version of this class
    public DocketType Withdrawal = new DocketType(2, "Withdrawal");
    public DocketType Installation = new DocketType(3, "Installation");

    // The publicly accessible static enumeration 
    public static DocketEnum Values = new DocketEnum();
}

// The actual value class
public class DocketType : EnumerationValue<DocketType, int, string>
{
        // Call through to the helper base constructor
    public DocketType(int docketTypeId, string description) 
        : base(docketTypeId, description) { }
}

// Base class for the enumeration
public abstract class EnumarationCollection<TType, X, Y>
    where TType : EnumerationValue<TType, X, Y> 
{
            // Resolve looks at the static Dictionary in the base helpers class
    public TType Resolve(X value)
    {
        return Cache[value] as TType;
    }

    public static Dictionary<X, EnumerationValue<TType, X, Y> > Cache = new Dictionary<X, EnumerationValue<TType, X, Y>>();
}

// Base class for the value
public abstract class EnumerationValue<TType, X, Y> 
    where TType : EnumerationValue<TType, X, Y> 
{        
        // helper constructer talks directly the the base helper class for the Enumeration
    protected EnumerationValue(X value, Y displayName)
    {
        EnumarationCollection<TType, X,Y >.Cache.Add(value, this as TType);
    }
}



class MainClass
{
    public static void Main (string[] args)
    {
                    // You can immediately resolve to the enumeration
        Console.WriteLine(DocketEnum.Values.Resolve(2).ToString());
    }
}

你想“对给定类型的所有子类”做点什么。如果不使用AppDomain.Current.GetAssemblies()并对其进行迭代,任何这种性质的操作都是不可能的。如果采用这种方法,可以通过创建仅应用于程序集(以及应包含在子类搜索中的其他程序集)的程序集级属性来优化性能,并在准备对每个程序集调用.GetTypes()时使用该属性。

为了清楚起见,下面是一个获取所有这些子类的示例:

Type[] subclasses = AppDomain.CurrentDomain.GetAssemblies()
    .Where(x => Attribute.IsDefined(typeof(MyEnumeartionAssemblyAttribute)))
    .SelectMany(x => x.GetTypes())
    .Where(x => x.BaseType != null && 
           x.BaseType.IsGenericType && 
           x.BaseType.GetGenericTypeDefinition() == typeof(Enumeration<,,>));

从这里开始,在每个系统上使用反射应该是一个简单的问题。

如果要强制运行另一个类的静态构造函数,可以使用 RuntimeHelpers.RunClassConstructor Enumeration<TEnum, X, Y> 以便在您第一次对泛型类型的任何实例化使用静态方法时运行它:

static Enumeration()
{
    RuntimeHelpers.RunClassConstructor(typeof(TEnum).TypeHandle);
}