The file BaseClasses.dll could not be added to the project

Problem

You get this error when opening your application in Visual Studio .NET:

The file 'bin\BaseClasses.dll' could not be added to the project.  A file with the same path already exists in the project.

The file 'bin\BaseClasses.Web.Controls.dll' could not be added to the project.  A file with the same path already exists in the project.

This usually occurs due to a bug in Visual Studio .NET 2003, though this may occur in other versions of Visual Studio .NET.  Visual Studio .NET maintains a cache of assemblies (DLLs) that sometimes becomes outdated and may contain references to old DLLs or DLLs that no longer exist.  (Note: BaseClasses.Web.Controls.dll is used in applications created by Iron Speed Designer V3.2 and earlier.  This DLL is not present in applications created by Iron Speed Designer V4.0 and later.)

Solution

See Error BC30002: Type XXX is not defined... for details.

See Also

Part IX:  Troubleshooting Applications

Application Generation and Compilation Error Messages