protected override SimpleOnPremiseEngine NewEngine(List <string> properties) { if (DataFileConfigs.Count != 1) { throw new Exception( "This builder requires one and only one configured file " + $"but it has {DataFileConfigs.Count}"); } var config = DataFileConfigs.First(); return(new SimpleOnPremiseEngine( config.DataFilePath, _loggerFactory.CreateLogger <SimpleOnPremiseEngine>(), CreateData, TempDir)); }