Framework Side .NET Framework Runtime Win32 API System.IO.File for .NET Framework My Class Library for .NET Framework My Application for .NET Framework Original .NET Core Windows Runtime Win32 API System.IO.File for .NET Core My Class Library for .NET Framework My Application for .NET Core .NET Coreで実行時 .NET CoreでBuild時 System.IO.File for .NET Framework My Class Library for .NET Framework My Application for .NET Core and Switch Bait