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Since I installed Visual Studio 2026 I keep having this problem where when I open a form the designer keeps giving me this error that doesn't specify what path has an illegal characters. I even tested if it's only for VS2022's projects, but even new projects have the same problem.
I've tried repairing VS2026 and reinstalling it, but I still get this error. Here's the Call Stack, If its needed or if it could help in any way:
at System.Security.Permissions.FileIOPermission.EmulateFileIOPermissionChecks(String fullPath) at System.IO.DirectoryInfo.Init(String path, Boolean checkHost) at Microsoft.WinForms.Utilities.Shared.ShadowCacheFolder.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.DotNet.DesignTools.Client.Host.ServerLayout.d__19.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.DotNet.DesignTools.Client.Host.ServerLayout.d__11.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.DotNet.DesignTools.Client.Host.ServerProcess.d__22.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.DotNet.DesignTools.Client.Host.ServerHostFactory.d__9.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.DotNet.DesignTools.Client.DesignToolsClientLoader.d__29.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.DotNet.DesignTools.Client.DesignToolsClientLoader.<>c__DisplayClass25_1.<<-ctor>b__1>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.DotNet.DesignTools.Client.DesignToolsClientLoader.d__27.MoveNext()
(For now I can't make a report on this problem directly to the VS Developer Community so...)
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Have you also tried creating a new folder with a simple, short name using Latin letters (e.g., C:\MyFolder1) and creating a new project there?
Yes and I still get the same error.
What is the full path of the project file (.csproj) and form files?
this happens after every VS update. and more than a year old solution still works