Some day ago, when i build my project i get unexpected error.

Error 3 The "CreateRiaClientFilesTask" task failed unexpectedly. System.Web.HttpException (0x80004005): Could not load file or assembly 'FileHelpers.DataLink' or one of its dependencies. Access is denied. ---> System.Configuration.ConfigurationErrorsException: Could not load file or assembly 'FileHelpers.DataLink' or one of its dependencies. Access is denied. ---> System.IO.FileLoadException: Could not load file or assembly 'FileHelpers.DataLink' or one of its dependencies. Access is denied..........

Sometime that happen when Visual studio cannot access files. so have to remove Temporary file.

I get simple solution from goggling, just close visual studio and reopen, and if Visual studio has no administrator rights then please right click to visual studio icon and choose "Run as a Administrator".

Then re-build project and problem solved.

Thanks.