regex: export excel cannot be open .xlsx

jeudi 13 août 2015

export excel cannot be open .xlsx

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.