So what do you do if you come across this error in Visual Studio?
System.Security.SecurityException: Request for the permission of type ‘System.Web.AspNetHostingPermission, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089’ failed.
The error typically occurs when you download files from an external source into your Visual Studio project. Windows will recognise the file came from an external source and restrict permissions.