Bug 42303 - Error Cannot create an instance of "WindowsPage"
Summary: Error Cannot create an instance of "WindowsPage"
Alias: None
Product: Forms
Classification: Xamarin
Component: Windows ()
Version: 2.3.4
Hardware: PC Windows
: Low normal
Target Milestone: ---
Assignee: Rui Marinho
Depends on:
Reported: 2016-07-01 08:28 UTC by the_klingon
Modified: 2017-06-21 13:11 UTC (History)
5 users (show)

Tags: ac, uwp, xaml
Is this bug a regression?: ---
Last known good build:

Exception in XamarinForms for WindowsPage (2.39 KB, text/plain)
2016-07-01 08:28 UTC, the_klingon

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Description the_klingon 2016-07-01 08:28:41 UTC
Created attachment 16542 [details]
Exception in XamarinForms for WindowsPage


I'm a problem about Xamarin.Forms.
OS: Windows 10 Pro
IDE: Visual Studio Community 2015 Update 3
Xamarin: Xamarin for VS

When I create a Xamarin.Forms Portable Project, I'm not able to use the designer in UWP and 8.1 (in 8.1 phone it works).
System return to me the following error: Error Cannot create an instance of "WindowsPage".
I followed the troubleshooting posted at https://developer.xamarin.com/guides/xamarin-forms/platform-features/windows/installation/universal/, but without result (however I found all modifies already done).

Can you help me about?

Thank you so much.

Comment 1 Rui Marinho 2016-07-04 11:44:18 UTC
Thank you for taking the time to submit the bug. We tried to reproduce the issue you reported but were unable given the description. If you could please attach a reproduction to the bug by starting with a clean Xamarin.Forms project and adding just the code necessary to demonstrate the issue, we would very much appreciate it. 

For your convenience, we have created some reproduction best practices viewable here: https://gist.github.com/jassmith/92405c300e54a01dcc6d

Warm regards,
Xamarin Forms Team
Comment 2 Georg Mischler 2017-01-17 09:21:56 UTC
To reproduce:

* Start Visual Studio
* create a new project (Xamarin.Forms portable)
* VS will possibly fail to correctly create the windows phone subprojects - which may or may not be a seperate issue.
* build the UWP subproject.
* In the UWP project, double click the file "MainPage.xaml"

Expected result:
* The XAML designer opens and shows a graphical representation of the file contents.

Actual result:
* The XAML designer displays a nested set of exceptions as in Alains attachment.

Since the other created subprojects only seem to let you edit the XAML as text, and the emulators are too sloggy for quick visual feedback on my system, that's quite the show stopper.

Environment in my case:
* Windows 10 pro
* VS 2015 4.6.01586
* Xamarin (according to "about VS")
* Xamarin for VS 4.2.8 (according to "Extensions and Updates")
* Microsoft.NetCore.UniversalWindowsPlatform v5.0.0 and v5.2.2
* Xamarin.Forms and
Comment 3 Rui Marinho 2017-06-20 18:05:00 UTC
can confirm using the steps above on VS2015 and 2.3.4. Not sure this is a Forms or VisualStudio problem.
Comment 4 David Ortinau [MSFT] 2017-06-21 13:11:15 UTC
This is working now in VS17.