public byte[] GetFileData(IEnumerable <TransactionDownloadLine> transactions) { var excelRows = new List <string[]> { GetHeaderRow() }; excelRows.AddRange(GetTransactionRows(transactions)); var transactionData = new Dictionary <string, string[][]> { { WorksheetName, excelRows.ToArray() } }; var fileData = _excelService.CreateExcelFile(transactionData); return(fileData); }