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Very occasionally when I navigate 'back' from a page on Windows Phone I get an error with the below details. I think I have only seen this on real devices and not the simulator, but not sure. Defintely happens sometimes on a Lumia 820.
As far as I can tell from the stack trace, this seems to be a bug in Xamarin's forms library and not my code.
System.InvalidOperationExceptionElement is already the child of another element.
at MS.Internal.XcpImports.CheckHResult(UInt32 hr)
at MS.Internal.XcpImports.Collection_AddValue[T](PresentationFrameworkCollection`1 collection, CValue value)
at MS.Internal.XcpImports.Collection_AddDependencyObject[T](PresentationFrameworkCollection`1 collection, DependencyObject value)
at System.Windows.PresentationFrameworkCollection`1.AddDependencyObject(DependencyObject value)
at System.Windows.Controls.UIElementCollection.AddInternal(UIElement value)
at System.Windows.PresentationFrameworkCollection`1.Add(T value)
at Xamarin.Forms.Platform.WinPhone.Platform.<>c__DisplayClass46.<SetCurrent>b__3e(Object s, EventArgs e)
at Microsoft.Phone.Controls.Transition.OnCompleted(Object sender, EventArgs e)
at MS.Internal.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args)
at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)
I have checked this issue but I am unable to reproduce this behavior, we may have to see if a developer can figure out what's going on from the stack trace. If you have a chance, it might also be helpful to include sample project, build info and logs (debug logs + IDE).
You can get build info from here:
Visual Studio => Help => About Microsoft Visual Studio => Copy Info
You can get IDE logs from here:
Visual Studio => Help => Zip Xamarin Logs
Thank you for taking the time to investigate, I appreciate that as it is an intermittent bug it is difficult to track down.
I haven't submitted a sample because it is intermittent and I cannot reliably reproduce it, so submitting a questionable sample seemed to do more harm than good. I was hoping an engineer could investigate based on the stack trace and figure it out.
Here is my VS build data in case it helps;
Microsoft Visual Studio Ultimate 2013
Version 12.0.31101.00 Update 4
Microsoft .NET Framework
Installed Version: Ultimate
Architecture and Modeling Tools 06181-004-0449004-02623
Microsoft Architecture and Modeling Tools
UML® and Unified Modeling Language™ are trademarks or registered trademarks of the Object Management Group, Inc. in the United States and other countries.
Team Explorer for Visual Studio 2013 06181-004-0449004-02623
Microsoft Team Explorer for Visual Studio 2013
Visual Basic 2013 06181-004-0449004-02623
Microsoft Visual Basic 2013
Visual C# 2013 06181-004-0449004-02623
Microsoft Visual C# 2013
Visual C++ 2013 06181-004-0449004-02623
Microsoft Visual C++ 2013
Visual F# 2013 06181-004-0449004-02623
Microsoft Visual F# 2013
Visual Studio 2013 Code Analysis Spell Checker 06181-004-0449004-02623
Microsoft® Visual Studio® 2013 Code Analysis Spell Checker
Portions of International CorrectSpell™ spelling correction system © 1993 by Lernout & Hauspie Speech Products N.V. All rights reserved.
The American Heritage® Dictionary of the English Language, Third Edition Copyright © 1992 Houghton Mifflin Company. Electronic version licensed from Lernout & Hauspie Speech Products N.V. All rights reserved.
Windows Phone SDK 8.0 - ENU 06181-004-0449004-02623
Windows Phone SDK 8.0 - ENU
.NET Memory Profiler 4.6
.NET Memory Profiler Visual Studio Integration Package
ASP.NET and Web Tools 12.4.51016.0
Microsoft Web Developer Tools contains the following components:
Support for creating and opening ASP.NET web projects
Browser Link: A communication channel between Visual Studio and browsers
Page Inspector: Inspection tool for ASP.NET web projects
Scaffolding: A framework for building and running code generators
Server Explorer extensions for Microsoft Azure Websites
Web publishing: Extensions for publishing ASP.NET web projects to hosting providers, on-premises servers, or Microsoft Azure
ASP.NET Web Frameworks and Tools 2012.2 4.1.21001.0
For additional information, visit http://go.microsoft.com/fwlink/?LinkID=309563
ASP.NET Web Frameworks and Tools 2013 5.2.21010.0
For additional information, visit http://www.asp.net/
Common Azure Tools 1.3
Provides common services for use by Azure Mobile Services and Microsoft Azure Tools.
Microsoft Advertising SDK for Windows Phone
Microsoft Advertising SDK for Windows Phone
Microsoft Azure HDInsight HQL Service 1.0.0000.0
Language service for Hive query
Microsoft Azure HDInsight Tools for Visual Studio 1.0.0000.0
An integrated development environment for HDInsight application development.
Microsoft Azure Mobile Services Tools 1.3
Microsoft Azure Mobile Services Tools
Microsoft Azure Tools 2.4
Microsoft Azure Tools for Microsoft Visual Studio 2013 - v2.4.20730.1601
Microsoft Azure Tools 2.5
Microsoft Azure Tools for Microsoft Visual Studio 2013 - v2.5.21104.1601
Microsoft Team Foundation Server 2013 Power Tools 12.0
Power Tools that extend the Team Foundation Server integration with Visual Studio.
Microsoft Visual Studio Process Editor 1.0
Process Editor for Microsoft Visual Studio Team Foundation Server
NuGet Package Manager 2.8.50926.663
NuGet Package Manager in Visual Studio. For more information about NuGet, visit http://docs.nuget.org/.
PowerShell Tools 1.3
Provides file classification services using PowerShell
PreEmptive Analytics Visualizer 1.2
Microsoft Visual Studio extension to visualize aggregated summaries from the PreEmptive Analytics product.
Release Management for Visual Studio Package 1.0
Release Management for Visual Studio
SQL Server Data Tools 12.0.41025.0
Microsoft SQL Server Data Tools
Windows Azure Tools 2.3
Windows Azure Tools for Microsoft Visual Studio 2013 - v2.3.20320.1602
Windows Phone 8.1 SDK Integration 1.0
This package integrates the tools for the Windows Phone 8.1 SDK into the menus and controls of Visual Studio.
Xamarin 22.214.171.124 (10cfd178d55287f09c85f5a1e604dfe20889a40f)
Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.
Xamarin.Android 126.96.36.199 (ba9bbbdd44cfdc4bf485e8885bd2ad24fba525f7)
Visual Studio plugin to enable development for Xamarin.Android.
Xamarin.iOS 188.8.131.52 (840a925103a0bf4a856507f13d5eaee3c1579c2f)
Visual Studio extension to enable development for Xamarin.iOS.
Provided as much useful info as I can at this point.
*** This bug has been marked as a duplicate of bug 25573 ***