Issue downloading .xlsm document with activex cont

I am trying to implement an excel file download functionality in my asp.net MVC application and using NPOI.

The file has three sheets and Sheet2 has two activex buttons.

I am reading the source file, adding values to sheet2, save it in temporary location and download the file later using the following code.

        using (var fs = new FileStream(xlsFilePath, FileMode.Open, FileAccess.Read))
        {
            var templateWorkbook = new XSSFWorkbook(fs);

            //Sheet update operation done here

            fs.Close();
            var memoryStream = new MemoryStream();
            templateWorkbook.Write(memoryStream);

            System.IO.File.WriteAllBytes(groupDocumentPath, memoryStream.ToArray());
        }

Issue: Because of the activex control the downloaded file is corrupt and when trying to open the file it is throwing an error:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<recoveryLog xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main"><logFileName>error728720_01.xml</logFileName><summary>Errors were detected in file 'C:\Users\dsekaran\Downloads\5B87FFF306BE8040D10B702 (5).xlsm'</summary><repairedParts><repairedPart>Repaired Part: /xl/worksheets/sheet2.xml part with XML error.  Catastrophic failure Line 1, column 0.</repairedPart></repairedParts><repairedRecords><repairedRecord>Repaired Records: Drawing from /xl/drawings/drawing1.xml part (Drawing shape)</repairedRecord></repairedRecords></recoveryLog>

Clarification: Does this mean NPOI doesn't support activex buttons? What can be done to overcome this issue?

you'll have to use correct MIME type while downloading the .xlsm file. I am downloading .xltm file after creating it through NPOI. See the below function

public ActionResult DownloadXLTMFile()
        {
            try
            {
               //Using Resposne Stream to Make File Available for User to Download;
                Response.Clear();

                Response.ContentType = "application/vnd.ms-excel.template.macroEnabled.12";
                Response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}",  "YourFileName.xltm"));

                Response.BinaryWrite(System.IO.File.ReadAllBytes(HostingEnvironment.MapPath("~/App_Data/YourManupulatedFile.xltm")));
                Response.End();
            }
            catch (Exception Ex)
            { 
            }
            finally
            {   }
            return View();
        }

check this link for appropriate MIME type