许久没搞WPF了，准备用WPF开发个小工具，新建工程，默认打开MainWindow.xaml，嗯.........

　　

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.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
   at Microsoft.VisualStudio.DesignTools.Utility.Telemetry.VsTelemetryService.RegisterDesignerProcessSession(Int32 pid)
   at Microsoft.VisualStudio.DesignTools.Utility.Feedback.WatsonTracker.RegisterSession(Int32 processID)
   at Microsoft.VisualStudio.DesignTools.Utility.DesignerSessionTracker.RecordDesignerStart(Int32 processID, String isolationTargetIdentifier, Boolean mockCustomTypes, String buildConfiguration)
   at Microsoft.VisualStudio.DesignTools.DesignerContract.Isolation.Primitives.ProcessDomainFactory.ProcessIsolationDomain..ctor(ProcessDomainFactory factory, IIsolationBoundary boundary, AppDomainSetup appDomainInfo, IIsolationTarget isolationTarget, String baseDirectory)
   at Microsoft.VisualStudio.DesignTools.DesignerContract.Isolation.Primitives.ProcessDomainFactory.CreateIsolationDomain(IIsolationBoundary boundary)
   at Microsoft.VisualStudio.DesignTools.DesignerContract.Isolation.Primitives.IsolationBoundary.Initialize()
   at Microsoft.VisualStudio.DesignTools.DesignerContract.Isolation.Primitives.IsolationBoundary.CreateInstance[T](Type type)
   at Microsoft.VisualStudio.DesignTools.DesignerContract.Isolation.IsolatedObjectFactory.Initialize()
   at Microsoft.VisualStudio.DesignTools.DesignerHost.Services.VSIsolationService.CreateObjectFactory(IIsolationTarget isolationTarget, IObjectCatalog catalog)
   at Microsoft.VisualStudio.DesignTools.DesignerContract.Isolation.IsolationService.CreateLease(IIsolationTarget isolationTarget)
   at Microsoft.VisualStudio.DesignTools.DesignerContract.IsolatedDesignerService.CreateLease(IIsolationTarget isolationTarget, CancellationToken cancelToken, DesignerServiceEntry& entry, IServiceProvider serviceOverrides)
   at Microsoft.VisualStudio.DesignTools.DesignerContract.IsolatedDesignerService.IsolatedDesignerView.CreateDesignerViewInfo(CancellationToken cancelToken)
   at Microsoft.VisualStudio.DesignTools.DesignerContract.Isolation.IsolatedTaskScheduler.InvokeWithCulture[T](CultureInfo culture, Func`2 func, CancellationToken cancelToken)
   at Microsoft.VisualStudio.DesignTools.DesignerContract.Isolation.IsolatedTaskScheduler.<>c__DisplayClass10_0`1.<StartTask>b__0()
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()

 

　　一顿搜索，/resetuserdata，用安装包修复，卸载重装都没用，就差重装系统了

解决：

vs安装的根目录下，有个Program文件，注意，是文件不是文件夹，可以用everything全盘搜一下，删除重新打开即可