Simple Injector fallback Registration of open generic not working

Question

I have the following

class GetData : Query
class Data : Result

class IHandler<TIn,TOut>
class IQueryHandler<TQuery,TResult> : IHandler<TQuery, IEnumerable<TResult>>
class DefaultQueryHandler<TQuery,TResult> : IQueryHander<TQuery,TResult>

Container.RegisterConditional(
    typeof(IHandler<,>),
    typeof(DefaultQueryHandler<,>),
    c => c!.Handled
)

I have followed the guide here https://simpleinjector.readthedocs.io/en/latest/advanced.html#registration-of-open-generic-types and thought that

Container.GetInstance<IHandler<GetData,IEnumerable<Data>>> should instantiate DefaultQueryHandler<GetData, Data>

But I get 'No registration found for IHandler'

Thank you

Answer 1

I tried to reproduce your error, but when I run it in a console application everything works as expected. Here is the code I used to reproduce:

using System;
using System.Collections.Generic;
using SimpleInjector;

class Query { }
class Result { }

class GetData : Query { }
class Data : Result { }

class IHandler<TIn, TOut> { }
class IQueryHandler<TQuery, TResult> : IHandler<TQuery, IEnumerable<TResult>> { }
class DefaultQueryHandler<TQuery, TResult> : IQueryHandler<TQuery, TResult> { }

class Program
{
    static void Main(string[] args)
    {
        var container = new Container();

        container.RegisterConditional(
            typeof(IHandler<,>),
            typeof(DefaultQueryHandler<,>),
            c => !c.Handled);

        var handler = container.GetInstance<IHandler<GetData, IEnumerable<Data>>>();

        Console.WriteLine(handler.GetType().FullName);
        Console.ReadLine();
    }
}

The GetInstance call returns the following closed type:

DefaultQueryHandler<GetData, Data>