Robert Jordan wrote:
> Andrés G. Aragoneses [ knocte ] wrote:
>> Robert Jordan escribió:
>>> Andrés G. Aragoneses [ knocte ] wrote:
>>>> Robert Jordan escribió:
>>>>> Andrés G. Aragoneses [ knocte ] wrote:
>>>>>> Today I've come out with this wish:
>>>>>>
>>>>>> Dictionary<typeof(T), List<T>> InternalCollection;
>>>>>>
>>>>>>
>>>>>> Of course, the compiler tells me an error, but I would want to know if I
>>>>>> can make this kind of collection with C# generics, in order to obtain
>>>>>> syntatic sugar and type safety, I mean:
>>>>>>
>>>>>> //compilation should succeed only if oMyObj is TypeX:T
>>>>>> InternalCollection.Add(typeof(TypeX), oMyObj);
>>>>>>
>>>>>> Any thoughts?
>>>>> class FooDictionary<T> : Dictionary<System.Type, T>
>>>>> {
>>>>> public void Add (T t)
>>>>> {
>>>>> this [typeof(T)] = t;
>>>>> }
>>>>> }
>>>>>
>>>> But that would only allow adding one object:
>>> Well, then use that slightly modified Add method:
>>>
>>> public void Add (T t)
>>> {
>>> if (t == null)
>>> throw new ArgumentNullException ("t");
>>> this [t.GetType ()] = t;
>>> }
>>>
>> Ok! But if I modify it to use lists, I get a compiler error:
>>
>> class FooDictionary<T> : Dictionary<Type, List<T>>
>> {
>> public void Add (List<T> t)
>> {
>> if (t == null)
>> {
>> throw new ArgumentNullException("t");
>> }
>> if (t.Count > 0)
>> {
>> this[t[0].GetType()] = t;
>> }
>> }
>> }
>>
>> ...
>>
>> FooDictionary<mytype> foo = new FooDictionary<mytype>();
>> foo.Add(new List<subtypeA>());
>>
>> Error 11 Argument '1': cannot convert from
>> 'System.Collections.Generic.List<subtypeA>' to
>> 'System.Collections.Generic.List<mytype>'
>>
>> However, it should allow it because subtypeA inherits from mytype,
>> right? I think I've reached a limitation of .NET generics, which I think
>> I read about here[1] :(
>
> This works, at least with MS.NET 2.0 csc:
>
> using System;
> using System.Collections.Generic;
>
> class FooDictionary<T> : Dictionary<System.Type, List<T>>
> {
> public void Add (List<T> t)
> {
> if (t == null)
> throw new ArgumentNullException ("t");
> // key is the generic argument of List<T>
> this [t.GetType ().GetGenericArguments() [0]] = t;
> }
> }
>
> class Test
> {
> static void Main ()
> {
> FooDictionary<int> d = new FooDictionary<int> ();
> d.Add (new List<int> ());
> }
> }
Scratch this. I didn't notice that you were using subclasses.
Robert
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