title: Can not implement interface in dotnet core
body: <p>I am very new to dotnet core and I am trying to create some simple test to see how it works. 
  I am creating a dotnet core project targeting framework 4.6.1
  My project.json looks like this:</p>
  
  <pre><code>{
      "version": "1.0.0-*",
      "buildOptions": {
          "preserveCompilationContext": true,
          "debugType": "portable",
          "emitEntryPoint": true
      },
      "dependencies": {},
      "frameworks": {
  
          "net461": {
              "dependencies": {
  
                  "Microsoft.AspNetCore.Server.Kestrel": "1.0.0",
                  "Microsoft.AspNetCore.Mvc": "1.0.0"
              },
              "imports": "dnxcore50"
          }
      }
  }
  
  using Microsoft.AspNetCore.Builder;
  using Microsoft.AspNetCore.Http;
  using Microsoft.Extensions.DependencyInjection;
  </code></pre>
  
  <p>My startup.cs</p>
  
  <pre><code>namespace TestWebCore3
  {
      public class Startup
      {
          public void ConfigureServices(IServiceCollection services)
          {
              services.AddMvc();
          }
          public void Configure(IApplicationBuilder app)
          {
              app.UseMvc();
              app.Run(context =&gt;
              {
              return context.Response.WriteAsync("Hello world");
              });
          }
      }
  }
  </code></pre>
  
  <p>my Program.cs</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Threading.Tasks;
  using Microsoft.AspNetCore.Hosting;
  using System.IO;
  
  
  namespace TestWebCore3
  {
      public class Program
      {
          public static void Main(string[] args)
          {
              var host = new WebHostBuilder()
              .UseKestrel()
              .UseContentRoot(Directory.GetCurrentDirectory())
              .UseStartup&lt;Startup&gt;()
              .Build();
  
              host.Run();
          }
      }
  }
  </code></pre>
  
  <p>Basically what I did so far was similar to using dotnet new, dotnet restore but changed to project.json to target framework 4.6.1 and it seemed to work when I ran dotnet run or ran from VS2015</p>
  
  <p>However, when I tried to create an interface, and a class derived from the interface, I have lost the intellisense and the project did not compile. I am new to dotnet core but I am not new to C#, but I am not sure what dependencies need to be included to get rid of the compiling error</p>
  
  <pre><code>Severity    Code    Description Project File    Line    Suppression State
  Error   CS0246  The type or namespace name 'IReceiptRepository' could not be found (are you missing a using directive or an assembly reference?)    TestWebCore3    D:\....\TestWebCore3\src\TestWebCore3\Infrastructure\ReceiptRepository.cs   8
  </code></pre>
  
  <p>My Receipt class is:</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Threading.Tasks;
  
      namespace TestWebCore3.Core
      {
          public class Receipt
          {
              public int Id { get; set; }
              public double Amount { get; set; }
              public string Description { get; set; }
              public DateTime TransactionDate { get; set; }
              public string Company { get; set; }
          }
  }
  </code></pre>
  
  <p>My interface:</p>
  
  <pre><code>using System.Collections.Generic;
  using System.Linq;
  using System.Threading.Tasks;
  namespace TestWebCore3.Core.Interface
  {
      public interface IReceiptRepository
      {
          IEnumerable&lt;Receipt&gt; List();
          Receipt GetById(int id);
          void Update(Receipt receipt);
      }
  }
  </code></pre>
  
  <p>My ReceiptRepository</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Threading.Tasks;
  
  namespace TestWebCore3.Infrastructure
  {
      public class ReceiptRepository : IReceiptRepository
      {
      }
  }
  </code></pre>
  
  <p>The structure of my project:</p>
  
  <p><a href="https://i.stack.imgur.com/YYd4r.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YYd4r.png" alt="enter image description here"></a></p>
  
  <p>I am confused as why the compiler does not recognize my interface. </p>
  
  <p>Does anyone what I did incorrectly?</p>