Cannot access Interface defined in the Code Sharing Project from within UWP project

I am just a newbie in Xamarin, so I tried creating the simple Phoneword application available at Xamarin on-line guides.

The solution created in Visual Studio comprises 4 distinct Projects:

1. A portable class library (PCL) project that holds all of the shared code
2. A project that holds Android specific code
3. A project that holds iOS specific code
4. A project that holds Universal Windows Platform (UWP) specific code

This is how the solution structure looks like:

Now inside the first project an interface has been declared:

namespace Phoneword
{
    public interface IDialer
    {
        bool Dial(string number);
    }
}

I now try to use this interface from within the UWP project:

using Phoneword.UWP;
using System;
using System.Threading.Tasks;
using Windows.ApplicationModel.Calls;
using Windows.UI.Popups;
using Xamarin.Forms;

[assembly: Dependency(typeof(PhoneDialer))]
namespace Phoneword.UWP
{
    public class PhoneDialer : IDialer
    {
      ...

Building the solution ends successfully. But when I try to Deploy the UWP project I get this error:

The type or namespace name 'IDialer' could not be found (are you missing a using directive or an assembly reference?)

Can anyone give me hint on what could be the source of this error?

Update

There was one more error I was getting when I tried to deploy:

Error DEP0700: Registration of the app failed. [0x80070005] error 0x80070005: Opening file from location: AppxManifest.xml failed with error: Access is denied.

I closed the solution, exited Visual Studio started and loaded again and the first error disappeared. So, it seems, there is nothing wrong in consuming an interface, declared in the Code Sharing Project, from within the UWP Project.

The actual error I was getting was due to access rights restrictions of the folder were the project was being deployed.

You are not referencing the Phoneword in your PhoneDialer.cs file. Add this to the top:

using Phoneword; // <== Add this
using Phoneword.UWP;
using System;
using System.Threading.Tasks;
using Windows.ApplicationModel.Calls;
using Windows.UI.Popups;
using Xamarin.Forms;