export excel cannot be open .xlsx - asp.net

Question

I am using asp.net C#, currently doing export excel file. I wish to export in .xlsx. everything seems fine until I open it. The code below is my code for export.
DataTable dt = GetData(sqlcommand);
if(dt.Rows.Count >0){
//Create a dummy GridView
GridView GridView1 = new GridView();
GridView1.AllowPaging = false;
GridView1.DataSource = dt;
GridView1.DataBind();
Response.Clear();
Response.Buffer = true;
Response.AddHeader("content-disposition", "attachment;filename=InventoryReport.xlsx");
Response.ContentEncoding = System.Text.Encoding.Unicode;
Response.BinaryWrite(System.Text.Encoding.Unicode.GetPreamble());
Response.Charset = "";
Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
StringWriter sw = new StringWriter();
HtmlTextWriter hw = new HtmlTextWriter(sw);
for (int i = 0; i < GridView1.Rows.Count; i++)
{
//Apply text style to each Row
GridView1.Rows[i].Attributes.Add("class", "textmode");
}
GridView1.RenderControl(hw);
//style to format numbers to string
string style = #"<style> .textmode { mso-number-format:\#; } </style>";
Response.Write(style);
Response.Output.Write(sw.ToString());
Response.Flush();
Response.End();
The image below is the error I got after open the .xlsx file.
I hope someone could help on my work. Thanks!! really appreciate if yo could help me on this.. much appreciate!

Answer 1

use my code
using OfficeOpenXml;
using System.Data;
namespace Managed_Leverage_BAL
{
public static class ExcelExportHelper
{
public static void CreateExcelFromDataSet(this DataSet dsReportData, string strFileNameWithPath, int[] DateFormatColumnNumbers = null)
{
if (File.Exists(strFileNameWithPath)) File.Delete(strFileNameWithPath);
FileInfo newFile = new FileInfo(strFileNameWithPath);
using (ExcelPackage pck = new ExcelPackage(newFile))
{
for (int tableIndex = 0; tableIndex < dsReportData.Tables.Count; tableIndex++)
{
DataTable tbl;
tbl = dsReportData.Tables[tableIndex];
ExcelWorksheet ws = pck.Workbook.Worksheets.Add(dsReportData.Tables[tableIndex].TableName);
ws.Cells["A1"].LoadFromDataTable(tbl, true);
if (tableIndex == 0)
for (int i = 0; i < DateFormatColumnNumbers.Count(); i++)
{
using (ExcelRange col = ws.Cells[DateFormatColumnNumbers[i], 1, DateFormatColumnNumbers[i] + tbl.Rows.Count, 1])
{
col.Style.Numberformat.Format = "dd-MMM-yyyy";
col.Style.HorizontalAlignment = ExcelHorizontalAlignment.Right;
}
}
string endHeader = "A";
for (int i = 0; i < tbl.Columns.Count - 1; i++)
{
endHeader = IncrementAlphabeticCounter(endHeader);
}
using (ExcelRange rng = ws.Cells["A1:" + endHeader + "1"])
{
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);
}
}
pck.Save();
}
}
public static char[] CheckZ(char[] cCounter, int iPos)
{
if (iPos >= 0)
{
if (cCounter[iPos] >= 'Z')
{
cCounter[iPos] = 'A';
if (iPos == 0)
{
char[] array = new char[cCounter.Length + 1];
cCounter.CopyTo(array, 1);
cCounter = array;
cCounter[0] = 'A';
return cCounter;
}
cCounter = CheckZ(cCounter, iPos - 1);
return cCounter;
}
cCounter[iPos] = (char)(cCounter[iPos] + '\x0001');
}
return cCounter;
}
public static string IncrementAlphabeticCounter(string sCounter)
{
if (sCounter == "")
{
return sCounter;
}
char[] cCounter = sCounter.ToCharArray();
return new string(CheckZ(cCounter, cCounter.Length - 1));
}
}
in page
private void Download(DataSet ds)
{
String strPath = Server.MapPath("~/Docs/") + "your path";
ds.CreateExcelFromDataSet(strPath);
Response.Clear();
Response.AddHeader("content-disposition", "attachment; filename=your file name.xlsx");
Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
Response.TransmitFile(strPath);
Response.Flush();
Response.End();
}
you will need epplus dll,get it here
http://download-codeplex.sec.s-msft.com/Download/Release?ProjectName=epplus&DownloadId=813458&FileTime=130743526623500000&Build=21028