dependency injection - Unable to resolve service for type 'Core.Data.CoreContext' while attempting to activate 'Core.Data.Repositories.UnitOfWork' -

i have part of webapi application want move separate project class library. common base structure every app has idea make easy shareable. application type is: asp.net core web application / .net framework - asp.net core 2.0 / web api

what have done in direction created project named core , moved shared elements there, including base entities (e.g. user, settings, etc), corecontext, unitofwork, generic repository, baserepositories,...

in main project of app there others entities, appcontext inherits corecontext, more repositories, , controllers, ...

i able build app when starting following error:

invalidoperationexception: unable resolve service type 'core.data.corecontext' while attempting activate 'core.data.repositories.unitofwork'.

microsoft.extensions.dependencyinjection.servicelookup.callsitefactory.createargumentcallsites(type servicetype, type implementationtype, iset callsitechain, parameterinfo[] parameters, bool throwifcallsitenotfound)...

problem seems unitofwork class in core project , in main project startup.cs method configureservices has services.addtransient<iunitofwork, unitofwork>();.

is bug or not configuring correctly , how achieved, if possible @ all?

*further technical details:
netcore & ef core version: 2.0
database provider: microsoft.entityframeworkcore.sqlserver
ide: visual studio 2017 15.3
operating system: windows 10

update: code sample

namespace main {     public class program     {         public static void main(string[] args)         {             buildwebhost(args).run();         }          public static iwebhost buildwebhost(string[] args) =>             webhost.createdefaultbuilder(args).usestartup<startup>().build();     }     public class startup     {         public startup(iconfiguration configuration)         {             configuration = configuration;         }         public iconfiguration configuration { get; }          public void configureservices(iservicecollection services)         {             services.addtransient<iunitofwork, unitofwork>();             services.addmvc();             var conn = configuration.getconnectionstring("defaultconnection");              services.adddbcontext<appcontext>(options => options.usesqlserver(conn));         }     } }  namespace main.data {     public class appcontext : corecontext     {         ...     } } 

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namespace core.data {     public class unitofwork : iunitofwork, idisposable     {         public corecontext context;          public unitofwork(corecontext context)         {             this.context = context;         }          public t get<t>() t : baserepository, new()         {             var repository = new t();             repository.init(context);             return repository;         }          public void dispose()         {             dispose(true);             gc.suppressfinalize(this);         }     } } 

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