Error in adding new Content Page to Xamarin.Forms app in Visual Studio 2017

Question

When I try to add a Content Page Visual studio throws a System.Exception error, and then this message box pops up:

This is the contents of the diagnostic log file:

10/02/2018 10:32:33 Recoverable
Microsoft.Assumes+InternalErrorException: Did not find new element in the hierarchy for item "Page1.xaml". The item would have been added with type "Page". The project item schema service knows about this item type. The item does exist in the project file.
   at Microsoft.Assumes.Fail(String message, Boolean showAssert)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.Automation.OAProjectItems.<EvaluateAddResultAsync>d__7.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.Automation.OAProjectItems.<>c__DisplayClass1_0.<<AddFromTemplate>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.Automation.OAProject.<>c__DisplayClass68_0`1.<<Mutate>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.ProjectNode.<>c__DisplayClass550_0.<<Mutate>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Threading.JoinableTask.CompleteOnCurrentThread()
   at Microsoft.VisualStudio.ProjectSystem.ProjectMultiThreadedService.ExecuteSynchronously(Func`1 asyncAction)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.ProjectNode.Mutate(Func`1 asyncAction, Boolean includesFileSystemChange, String telemetryActivity)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.Automation.OAProject.Mutate[T](Func`1 asyncAction, Boolean includesFileSystemChange, String telemetryActivity)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.Automation.OAProjectItems.AddFromTemplate(String fileName, String name)
   at Microsoft.VisualStudio.TemplateWizard.Wizard.EnumContentsAddItem(ProjectItems projectItems, XmlNode contentNode, String projectName, String currentFolder, String currentTargetFolder, String rootName, String templateFolderPath, String destinationRootFolderPath, String userSpecifiedDestItemPath, String projectTypeString, List`1 wizardExtensions, String rootExtension)
   at Microsoft.VisualStudio.TemplateWizard.Wizard.Execute(Object application, Int32 hwndOwner, Object[]& ContextParams, Object[]& CustomParams, wizardResult& retval)
   at System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(Int32 errorCode, IntPtr errorInfo)
   at Microsoft.VisualStudio.ErrorHandler.ThrowOnFailure(Int32 hr, Int32[] expectedHRFailure)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.ProjectNode.RunWizard(SimpleHierarchyNode parentNode, String itemName, String wizardToRun, IntPtr dlgOwner)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.ProjectNode.<AddItemWithSpecificAsync>d__592.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.ProjectNode.<>c__DisplayClass457_0.<<AddItem>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Threading.JoinableTask.CompleteOnCurrentThread()
   at Microsoft.VisualStudio.Threading.JoinableTask`1.CompleteOnCurrentThread()
   at Microsoft.VisualStudio.ProjectSystem.ProjectMultiThreadedService.ExecuteSynchronously[T](Func`1 asyncAction)
   at Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.ProjectNode.<>c__DisplayClass549_0.<HrInvoke>b__0()
   at Microsoft.VisualStudio.ProjectSystem.VS.HResult.Invoke(Func`1 action, IServiceProvider vsShellServiceProvider, IProjectFaultHandlerService projectFaultHandlerService, UnconfiguredProject project)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.VisualStudio.ProjectSystem.CommonProjectSystemTools.Rethrow(Exception ex)
   at Microsoft.VisualStudio.ProjectSystem.ProjectErrorReporting.<>c__DisplayClass6_0.<SubmitErrorReport>b__0()
   at Microsoft.VisualStudio.ProjectSystem.ExceptionFilter.<>c__DisplayClass2_0.<Guard>b__0()
   at GuardMethodClass.GuardMethod(Func`1 , Func`2 , Func`2 )

I have just installed Xamarin and Visual Studio after reformatting my PC, and I have never had this issue before. Can someone please help me solve this problem?

EDIT:

Initially, I believed the problem was caused by another application that I installed. I uninstalled IntelliJ and Android Studio (by JetBrains), now I can add the Content Page , but only the xaml.cs file is added to the project. However, when I check in file explorer, the xaml file is in the same folder but not in the project.

I can still edit the xaml file, but it comes up with the error:

The name 'InitializeComponent' does not exist in the current context.

This is the contents of the xaml file:

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="App1.Views.Page1">
    <ContentPage.Content>
        <StackLayout>
            <Label Text="Welcome to Xamarin.Forms!\nThis is page 2!!!"
                VerticalOptions="CenterAndExpand" 
                HorizontalOptions="CenterAndExpand" />
        </StackLayout>
    </ContentPage.Content>
</ContentPage>

And this is the contents of the xaml.cs file:

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace App1.Views
{
    [XamlCompilation(XamlCompilationOptions.Compile)] // <-- I don't remember this being here before. 
    public partial class Page1 : ContentPage
    {
        public Page1 ()
        {
            InitializeComponent ();
        }
    }
}

Answer 1

Irritatingly, it seems that a simple reinstallation of Visual Studio solved the problem. I can now add a Content Page without any issues.

Update:

This issue is a bug which has already been reported to Xamarin. The best workaround for this problem is to install the UWP workload alongside Xamarin, this removes the error.