public FileStreamResult DownloadExcelFile(DataTable dt, string filename)

        {

            //New instance of ExcelEngine is created 

​

            //Equivalent to launching Microsoft Excel with no workbooks open

​

            //Instantiate the spreadsheet creation engine

​

            ExcelEngine excelEngine = new ExcelEngine();

​

            //Instantiate the Excel application object

​

            IApplication application = excelEngine.Excel;

​

            //Assigns default application version

​

            application.DefaultVersion = ExcelVersion.Excel2013;

​

            //A new workbook is created.              

​

            IWorkbook workbook = application.Workbooks.Create(1);

​

            //Access first worksheet from the workbook.

​

            IWorksheet worksheet = workbook.Worksheets[0];

​

            //Defining the ContentType for excel file.

​

            string ContentType = "Application/msexcel";

​

            //Define the file name.

​

​

​

            //Creating stream object.

            MemoryStream memstream = new MemoryStream();

​

​

            //Saving the workbook to stream in XLSX format

​

            workbook.SaveAs(memstream);

​

            memstream.Position = 0;

​

            //Closing the workbook.

​

            workbook.Close();

​

            //Dispose the Excel engine

​

            excelEngine.Dispose();

​

            //Creates a FileContentResult object by using the file contents, content type, and file name.

            return File(memstream, ContentType, filename);

​

        }