The layout could not be loaded

Problem

xamarin android designer suddenly displays an error message like this

System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
   at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
   at Roslyn.Utilities.ObjectWriter.WriteKnownType(Type type)
   at Roslyn.Utilities.ObjectWriter.WriteObjectHeader(Object instance, UInt32 memberCount)
   at Roslyn.Utilities.ObjectWriter.WriteObjectInternal(IObjectWritable instance)
   at Xamarin.AndroidDesigner.Resources.Ast.ResourceRepositorySerializer.SerializeResourcesForJava(IEnumerable`1 resources, Int32 originalCount, Stream stream, IEnumerable`1 qualifiersToMatch)
   at Xamarin.AndroidDesigner.Resources.Ast.ResourceRepository.SerializeForJavaTo(Stream stream, IEnumerable`1 toMatch)
   at Xamarin.AndroidDesigner.Resources.Ast.ResourceProvisionator.SerializeRepositoryToFilePath(ResourceRepository repository, String path, IEnumerable`1 qualifiers)
   at Xamarin.AndroidDesigner.Resources.Ast.ResourceProvisionator.<>c__DisplayClass5_1.<CreateSerializationTasks>b__0()
   at System.Threading.Tasks.Task.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
--- 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 Xamarin.AndroidDesigner.Resources.Ast.ResourceProvisionator.<ProvisionResources>d__4.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 Xamarin.AndroidDesigner.ResourceProvisionatorExtensions.<ProvisionResources>d__0.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 Xamarin.AndroidDesigner.AndroidRenderSession.<InitSession>d__115.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.VisualStudio.Telemetry.WindowsErrorReporting.WatsonReport.GetClrWatsonExceptionInfo(Exception exceptionObject)

after that, all the layout show the same error message

What I've Do

• Repair Visual Studio