Generating Excel Documents with ASP.NET Website

Question

I have an ASP.NET application that helps the user create a Gridview with certain data in it. Once this table is generated I want the user to push a button and be able to save the table as an Excel document.There are two different methods I know of:

Using HtmlTextWriter with ContentType "application/vnd.ms-excel" to send the file as an HttpResponse. I use GridView1.RenderControl(htmlTextWriter) to render the gridview. This almost works, but the excel file always shows a warning when the file opens because the content doesn't match the extension. I have tried various content types to no avail. This makes sense I guess, because I'm using an HtmlWriter. It also doesn't seem a good practice.
The second thing I've tried is generating the Excel file using Office Automation. But for the file to be generated, I need to save it to disk and then read it again. From what I have read, this is the only way, because the Excel object only becomes a real Excel file once you save it. I found that the .saveas method from the Excel class would throw an exception because of write permissions, even if I tried to save in the App_Data folder. So I did some research and found that apparently Office Automation is discouraged for web services: https://support.microsoft.com/en-us/kb/257757

Microsoft does not currently recommend, and does not support, Automation of Microsoft Office applications from any unattended, non-interactive client application or component (including ASP, ASP.NET, DCOM, and NT Services), because Office may exhibit unstable behavior and/or deadlock when Office is run in this environment.

There surely must be a save way to have a website generate an Excel file and offer it to the user!? I can't imagine that this problem is unsolved or so rare that nobody cares about it, but yet I can't find any good solution to this.

Thorarins Thorarins · Accepted Answer · 2015-10-23T13:19:49

the easiest (and best) way to create an excel file is by using epplus

Epplus sample for webapplication

            using (ExcelPackage pck = new ExcelPackage())
            {
                ExcelWorksheet ws = pck.Workbook.Worksheets.Add("Demo");

                //Load the datatable into the sheet, starting from cell A1. Print the column names on row 1
                ws.Cells["A1"].LoadFromDataTable(tbl, true);

                //Format the header for column 1-3
                using (ExcelRange rng = ws.Cells["A1:C1"])
                {
                    rng.Style.Font.Bold = true;
                    rng.Style.Fill.PatternType = ExcelFillStyle.Solid;                      //Set Pattern for the background to Solid
                    rng.Style.Fill.BackgroundColor.SetColor(Color.FromArgb(79, 129, 189));  //Set color to dark blue
                    rng.Style.Font.Color.SetColor(Color.White);
                }

                //Example how to Format Column 1 as numeric 
                using (ExcelRange col = ws.Cells[2, 1, 2 + tbl.Rows.Count, 1])
                {
                    col.Style.Numberformat.Format = "#,##0.00";
                    col.Style.HorizontalAlignment = ExcelHorizontalAlignment.Right;
                }

                //Write it back to the client
                Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
                Response.AddHeader("content-disposition", "attachment;  filename=ExcelDemo.xlsx");
                Response.BinaryWrite(pck.GetAsByteArray());
}

Generating Excel Documents with ASP.NET Website

1 Answers