在这个.NET代码中遇到Generics的问题

Question

i'm trying to make a mixed collection of Types. I know the types at the start.. but I can't seem to figure out the syntax to make the collection, etc.

eg.

....
// I leave the typo there, for embarrassment :(
Initialize(new []{ typeof(Cat), typeof(Dog), typeof(JohnSkeet) }); 
...

public Foo Initialize(IEnumerable<Type> types)
{
   // for each type, set up the inmemory storage.
   foreach(var type in types)
   {
       // ????
       // Create an empty list, which will only contain this 'type'
       // I'm guessing, an IDictionary<type, ICollection<type>>().. thingy ?
   }
}

public ICollection<Type> SomeTypeData(Type type)
{
    // Return the collection, for this type.
}

Does this mane sense? Is this possible?

Answer 1

好吧,既然我认为我知道你想要什么,它看起来像这样:

// This can't really be *properly* statically typed
private readonly Dictionary<Type, object> typeMap = new 
    Dictionary<Type, object>();

public Foo Initialize(IEnumerable<Type> types)
{
   Type genericListType = typeof(List<>);
   foreach(var type in types)
   {
       // MakeGenericType is really badly named
       Type constructedListType = genericListType.MakeGenericType(type);
       typeMap[type] = Activator.CreateInstance(constructedListType);
   }
}

// We can't express this particularly safely either,
// although we *could* return the non-generic IList
public object SomeTypeData(Type type)
{
    return typeMap[type];
}

// This *is* statically typed, although we need to cast inside
public IList<T> SomeTypeData<T>()
{
    return (IList<T>) typeMap[typeof(T)];
}

有关类似示例,请参阅此博客文章.

请注意,基本上你试图用内部字典类型表示泛型根本无法处理的东西......并且第一种形式SomeTypeData也不能静态输入...因为这意味着知道类型在编译时我们只会在执行时实际给出它.