private void ClearOnFailingToCompile(string dllPathFile, string modelsHashFile, string projFile)
        {
            _logger.LogDebug("Failed to compile.");

            // the dll file reference still points to the previous dll, which is obsolete
            // now and will be deleted by ASP.NET eventually, so better clear that reference.
            // also touch the proj file to force views to recompile - don't delete as it's
            // useful to have the source around for debugging.
            try
            {
                if (File.Exists(dllPathFile))
                {
                    File.Delete(dllPathFile);
                }

                if (File.Exists(modelsHashFile))
                {
                    File.Delete(modelsHashFile);
                }

                if (File.Exists(projFile))
                {
                    File.SetLastWriteTime(projFile, DateTime.Now);
                }
            }
            catch
            { /* enough */
            }
        }