using System;

using System.Collections.Generic;

​

namespace Example

{

    class BaseResponse

    {

    }

​

    class PostResponse : BaseResponse

    {

        //...

    }

​

    class PhotoResponse : BaseResponse

    {

        //...

    }

​

    interface IBaseRequest<out TReply> where TReply : BaseResponse, new()

    {

        //...

    }

​

    class PostRequest : IBaseRequest<PostResponse>

    {

        //...

    }

​

    class PhotoRequest : IBaseRequest<PhotoResponse>

    {

        //...

    }

​

    class Service

    {

        public TReply Perform<TReply>(IBaseRequest<TReply> request) where TReply : BaseResponse, new()

        {

            return new TReply();

        }

    }

​

    public class Program

    {

        public static void Main()

        {

            var client =  new Service();

            var request = new PostRequest();

            var response = client.Perform(request); //Compiler will infer response = PostResponse

        }

    }

}

​