An error occured while loading the Resource Explorer: An item with the same key has already been added.

[WolfgangHG]

This error happens when opening a resx file with the new Resource Explorer in Visual Studio 17.11.0:

System.ArgumentException: An item with the same key has already been added.
   at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer)
   at Microsoft.VisualStudio.ResourceExplorer.Utils.DisplayPathUtils.GetResourceGroupTreeNodeName(String baseName, Project project, ImmutableArray`1 parseResults)
   at Microsoft.VisualStudio.ResourceExplorer.UI.NavTree.NavigationTreeViewModel.CreateResourceGroupNode(HashSet`1 nodesToCheck, SolutionContext solutionContext, ResourceGroupParseResult resourceGroupParseResult, ResourceTreeNode projectNode, ImmutableArray`1 projectParseResults)
   at Microsoft.VisualStudio.ResourceExplorer.UI.NavTree.NavigationTreeViewModel.<>c__DisplayClass10_0. <CreateProjectNode>b__2(ResourceGroupParseResult result)
   at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Microsoft.VisualStudio.ResourceExplorer.UI.NavTree.NavigationTreeViewModel.<>c__DisplayClass10_0. <CreateProjectNode>g__AddChildNodesToProjectNode|1()
   at Microsoft.VisualStudio.ResourceExplorer.UI.NavTree.NavigationTreeViewModel.CreateProjectNode(HashSet`1 nodesToCheck, ProjectContext projectContext, ProjectUpdateType update)
   at Microsoft.VisualStudio.ResourceExplorer.UI.NavTree.NavigationTreeViewModel. <OnProjectUpdate>g__HandleProjectAdded|8_0(ProjectContext projectContext, ProjectUpdate update)
   at Microsoft.VisualStudio.ResourceExplorer.UI.NavTree.NavigationTreeViewModel.OnProjectUpdate(ProjectUpdate update)
   at Microsoft.VisualStudio.ResourceExplorer.SolutionContext.NotifyProjectAdded(ProjectContext projectContext)
   at Microsoft.VisualStudio.ResourceExplorer.IO.SolutionLoader. <HandleProjectLoadAsync>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.ResourceExplorer.IO.SolutionLoader. <LoadSolutionAsync>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.ResourceExplorer.UI.ResourceExplorerControl.<>c__DisplayClass2_0. <<TryPopulateSolution>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.ResourceExplorer.UI.AsyncLoadContent.<>c__DisplayClass0_0. <<Initialize>b__0>d.MoveNext()

We have a large solution (about 100 projects) with a lot of resx files with string values or images. We also have “Properties\Resources.resx” files in most projects. But the issue also happens when opening a WinForms resx file.

I tried to reproduce it with a small sample, but did not succeed. So it must be related to the size of the solution or something special.

Workaround: right click on resx file => “Open with” ==> “Managed Resources Editor (Legacy)”.

While debugging VS, I noticed a lot of FileNotFoundExceptions like this - don’t know whether they are related:

System.IO.DirectoryNotFoundException
  HResult=0x80070003
  Message=Could not find a part of the path 'E:\Projekte\Tools\DEV\DLLs\HG. ApplicationBase.Guiwin\Web\Controls\Resources\nav_refresh_blue_16x16.ico'.
  Source=mscorlib
  StackTrace:
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) in System.IO\__Error.cs:line 135

>	mscorlib.dll! System.IO.__Error.WinIOError(int errorCode, string maybeFullPath) Line 133	C#
 	mscorlib.dll! System.IO.FileStream.Init(string path, System.IO.FileMode mode, System.IO.FileAccess access, int rights, bool useRights, System.IO.FileShare share, int bufferSize, System.IO.FileOptions options, Microsoft.Win32.Win32Native.SECURITY_ATTRIBUTES secAttrs, string msgPath, bool bFromProxy, bool useLongPath, bool checkHost) Line 710	C#
 	mscorlib.dll! System.IO.FileStream.FileStream(string path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share) Line 352	C#
 	System.Windows.Forms.dll! System.Resources.ResXFileRef.Converter.ConvertFrom(System.ComponentModel.ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value)	Unknown
 	System.Windows.Forms.dll! System.Resources.ResXDataNode.GetValue(System.ComponentModel.Design.ITypeResolutionService typeResolver)	Unknown
 	Microsoft.VisualStudio.ResourceExplorer.dll! Microsoft.VisualStudio.ResourceExplorer.IO.ResxResourceParser.GetNodeValue(string path, System.Resources.ResXDataNode node) Line 239	C#
 	Microsoft.VisualStudio.ResourceExplorer.dll! Microsoft.VisualStudio.ResourceExplorer.IO.ResxResourceParser.TryParseNodeValue(string localizedPath, System.Resources.ResXDataNode node) Line 217	C#
 	Microsoft.VisualStudio.ResourceExplorer.dll! Microsoft.VisualStudio.ResourceExplorer.IO.ResxResourceParser.ParseGroup(Microsoft.VisualStudio.ResourceExplorer.IO.ResourceGroupParseResult existingParseResult, string baseName, string neutralFilePath, System.Collections.Immutable.ImmutableArray<(string Path, string Culture)> localizablePaths, System.Collections.Generic.IReadOnlyCollection<string> selectedGroupBasePaths, Microsoft.VisualStudio.ResourceExplorer.IO.IRdtDocumentManager rdtDocumentManager, Microsoft.VisualStudio.ResourceExplorer.Model.Project project, System.Threading.CancellationToken token, out System.Collections.Immutable.ImmutableDictionary<string, Microsoft.VisualStudio.ResourceExplorer.Model.ResourceFileLoadException> loadExceptionsByCulture, out Microsoft.VisualStudio.ResourceExplorer.Model.ResourceFileType resourceFileType) Line 87	C#
 	Microsoft.VisualStudio.ResourceExplorer.dll! Microsoft.VisualStudio.ResourceExplorer.IO.Resx.ProjectResourceLoader.ParseGroup(Microsoft.VisualStudio.ResourceExplorer.IO.ResourceGroupParseResult existingParseResult, string baseName, string neutralFilePath, System.Collections.Immutable.ImmutableArray<(string Path, string Culture)> localizedFiles, System.Collections.Generic.IReadOnlyCollection<string> selectedGroupBasePaths, bool? shouldBeSelected, Microsoft.VisualStudio.ResourceExplorer.Model.Project project, Microsoft.VisualStudio.ResourceExplorer.IO.IRdtDocumentManager rdtDocumentManager, System.Threading.CancellationToken token) Line 48	C#
 	Microsoft.VisualStudio.ResourceExplorer.dll! Microsoft.VisualStudio.ResourceExplorer.IO.SolutionLoader.LoadInitialFilesInProjectAsync.AnonymousMethod__3(Microsoft.VisualStudio.ResourceExplorer.IO.ResxFileGrouping group) Line 160	C#
 	System.Core.dll! System.Linq.Parallel.SelectQueryOperator<System.__Canon, System.__Canon>. SelectQueryOperatorEnumerator<int>. MoveNext(ref System.__Canon currentElement, ref int currentKey)	Unknown
 	System.Core.dll! System.Linq.Parallel.PipelineSpoolingTask<System.__Canon, int>. SpoolingWork()	Unknown
 	System.Core.dll! System.Linq.Parallel.SpoolingTaskBase.Work()	Unknown
 	System.Core.dll! System.Linq.Parallel.QueryTask.BaseWork(object unused)	Unknown
 	mscorlib.dll! System.Threading.Tasks.Task.Execute() Line 2514	C#
 	mscorlib.dll! System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 515	C#
 	mscorlib.dll! System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) Line 486	C#
 	mscorlib.dll! System.Threading.Tasks.Task.ExecuteWithThreadLocal(ref System.Threading.Tasks.Task currentTaskSlot) Line 2684	C#
 	mscorlib.dll! System.Threading.Tasks.Task.ExecuteEntry(bool bPreventDoubleExecution) Line 2630	C#
 	mscorlib.dll! System.Threading.ThreadPoolWorkQueue.Dispatch() Line 569	C#

Interesting here is that “nav_refresh_blue_16x16.ico” is declared in “E:\Projekte\Tools\DEV\DLLs\Personenpool\PersonenpoolGui\PersonenpoolGui.csproj\Properties\Resources.resx”:

  <data name="nav_refresh_blue_16x16" type="System.Resources.ResXFileRef, System.Windows.Forms">
    <value>.. \Controls\Resources\nav_refresh_blue_16x16.ico; System.Drawing.Bitmap, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a</value>
  </data>

The directory “E:\Projekte\Tools\DEV\DLLs\HG. ApplicationBase.Guiwin\Web\Controls” does not exist. So, maybe some current path is not properly reset when traversing the solution?
The solution is placed at “E:\Projekte\Tools\DEV”, and all projects are in “E:\Projekte\Tools\DEV\DLLs”, some in sub directories.

Unfortunately, I cannot watch variable values while debugging, so I cannot provide more details.

[WolfgangHG]

Initially posted here: https://developercommunity.visualstudio.com/t/17110-An-error-occured-while-loading/10723554

[haileymck]

Hi @WolfgangHG, thank you for filing a Feedback ticket. We will continue to track the issue there. I will close this issue as to not have duplicate issues, so please follow up on the other ticket with further discussion. Thank you!