按类型处理对象列表

Question

I have a requirement to create a Sync method. 1) On input it takes SyncRequest object.

class SyncRequest{
    public List<SyncObj> Objects{get;set;}
}
class SyncObj{
    public Type Type{get;set;}
    public object Object{get;set;}
}

2) Based on type of each object i need to use different service to proceed and the different repository to persist the data.

Ie if i got the 3 objects with types User, User, Task. I will group them by type, and then Proceed with UserService and TaskService.
I'm trying to architect my web.api with Onion Architecture. Where DataAccess, Core, Services are separated of each other. And i want avoid swich or if's, in my code.

All ideas i came up was ugly. For example Dicitionary<Type, Service> , and manual casting.

I feel that Ninject might have really beatifull answer on my problem, with some factory functionality, but i can't come up with it.

Can anyone describe how this pattern should work. Or how this pattern calls, where to read.

Answer 1

Since all you've got is a Type one way or another you're going to have to use Reflection. The other question is how you're accessing the DI container (ninject kernel).

You can do something like this:

public interface IHandler<T>
{
    void Handle(T obj);
}

public void UserService : IHandler<User> {...}

Bind<IHandler<User>>().To<UserService>();

which you would then use like this:

foreach(var syncObj in syncRequest.Objects) 
{
    Type handlerType = typeof(IHandler<>).MakeGeneric(syncObj.Type);
    MethodInfo handleMethod = handlerType.GetMethod("Handle");

    object handler = kernel.Get(handlerType);

    handleMethod.Invoke(handler, new object[] { syncObj.Object });
}

As you see you'll need access to the container somehow to create the specific type. You can have it injected as IResolutionRoot . To adhere to the Onion Layering you'll have to move the code that uses the kernel to the composition root and give it an interface... Since you seem to know about onion layering i won't go into more detail :)