The project system has encountered an error When trying to load project

Question

In Visual Studio 2017 v15.7.1 I am getting the following error window when trying to load one of my projects:

And when I go to the path specified, inside the test file I find a very long stack-trace which I could not copy all of it because it exceeds allowed characters count.

===================== 5/31/2018 3:40:57 PM LimitedFunctionality System.AggregateException: Project system data flow 'ProjectBuildSnapshotService Outer 320459' closed because of an exception: System.AggregateException: One or more errors occurred. ---> System.AggregateException: One or more errors occurred. ---> System.AggregateException: One or more errors occurred. ---> System.AggregateException: One or more errors occurred. ---> System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.VisualStudio.ProjectServices.DesignTimeBuilder.d__17.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.Build.DesignTimeBuilderService.BuilderLifetimeHelper.d__12.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.Build.DesignTimeBuilderService.d__36.MoveNext() --- End of stack trace from previous location where exception was thrown --- at Microsoft.VisualStudio.ProjectSystem.Build.DesignTimeBuilderService.d__36.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 System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
at Microsoft.VisualStudio.ProjectSystem.Build.DesignTimeBuildManagerService.d__55.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 System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
at Microsoft.VisualStudio.ProjectSystem.Build.DesignTimeBuildManagerService.d__53.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.Designers.ProjectBuildSnapshotService.d__74.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 System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
at Microsoft.VisualStudio.ProjectSystem.Designers.ProjectBuildSnapshotService.<>c__DisplayClass72_0.<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.d__78.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.JoinableTask1.<JoinAsync>d__3.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.Designers.ProjectBuildSnapshotService.<UpdateSnapshotCoreAsync>d__72.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 System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
at Microsoft.VisualStudio.ProjectSystem.Designers.CustomizableBlockSubscriberBase3.d__34.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.Designers.CustomizableBlockSubscriberBase3.<>c__DisplayClass32_0.<<Initialize>b__1>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.<JoinAsync>d__78.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.Designers.CustomizableBlockSubscriberBase3.<b__32_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.DataflowExtensions.<>c__DisplayClass24_0`2.<b__0>d.MoveNext()

Answer 1

I found that you need to do two steps to resolve this issue:

1. Delete the .vs folder at the solution level.
2. Delete the bin and obj folders in all projects within the solution.

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I encountered the issue in Visual Studio 2017 v15.7.4 and the affected project/solution was created in v15.7.4, so it can occur without upgrading to a new version of Visual Studio.

Answer 2

Try deleting bin and obj folders in all projects of that solution.

Probably those folders were having old files generated by some older version of visual studio, which are not compatible with new version of visual studio.