The namespace 'x' already contains a definition for 'y'

Hi,

With VS 2017 release I have created a new Xamarin.Forms Blank App (PCL) name App5.
Right click on App5(Portable) Add -> New Item... and choose "Forms MasterDetail Page Xaml" and default for Name "Page1.xaml" and hit Add.

Trying to Build the project and two errors are raising:

Severity Code Description Project File Line Suppression State
Error CS0101 The namespace 'App5' already contains a definition for 'Page1' App5 C:\Xamarin Projects\App5\App5\App5\obj\Debug\App5.Page1.xaml.g.cs 17 Active

Severity Code Description Project File Line Suppression State
Error The "ResolveLibraryProjectImports" task failed unexpectedly.
System.IO.FileNotFoundException: Could not load assembly 'App5, Version=0.0.0.0, Culture=neutral, PublicKeyToken='. Perhaps it doesn't exist in the Mono for Android profile?
File name: 'App5.dll'
at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.Resolve(AssemblyNameReference reference, ReaderParameters parameters)
at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.Resolve(String fullName, ReaderParameters parameters)
at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.Resolve(String fullName)
at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.GetAssembly(String fileName)
at Xamarin.Android.Tasks.ResolveLibraryProjectImports.Extract(DirectoryAssemblyResolver res, ICollection1 jars, ICollection1 resolvedResourceDirectories, ICollection1 resolvedAssetDirectories, ICollection1 resolvedEnvironments)
at Xamarin.Android.Tasks.ResolveLibraryProjectImports.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.d__26.MoveNext() App5.Android

Thanks in advanced for any help,
Asaf