I followed your below link

Export RDLC Report to PDF and send in Email as Attachment using C# and VB.Net in ASP.Net

in which pdf is being sent and opened, but when i convert it to excel, then excel file is not getting open in email attachment

        con.Open();
        SqlCommand cmd = new SqlCommand("SP_Employee_Day_Status", con);
        cmd.CommandType = CommandType.StoredProcedure;
 
        SqlCommand cmd1 = new SqlCommand("SP_Get_Current_Attendance", con);
        cmd1.CommandType = CommandType.StoredProcedure;
 
        cmd.Parameters.AddWithValue("@DateFrom", txtDateFrom.Text);
        cmd.Parameters.AddWithValue("@DateTo", txtDateTo.Text);
 
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
 
        SqlDataAdapter da1 = new SqlDataAdapter(cmd1);
        DataSet ds1 = new DataSet();
        da1.Fill(ds1);
 
 
        ReportDataSource rds = new ReportDataSource();
        rds.Name = "DSDay";
        rds.Value = ds.Tables[0];
 
        ReportDataSource rds1 = new ReportDataSource();
        rds1.Name = "DStime";
        rds1.Value = ds1.Tables[0];
 
 
 
        ReportViewer1.LocalReport.DataSources.Clear();
        ReportViewer1.LocalReport.ReportPath = "daystats.rdlc";
        ReportViewer1.LocalReport.DataSources.Add(rds);
        ReportViewer1.LocalReport.DataSources.Add(rds1);
        ReportViewer1.LocalReport.Refresh();
 
 
        ReportViewer1.Visible = true;
        con.Close();
 
        SendEmail();
    }
}
 
private void SendEmail()
{
    using (MailMessage mm = new MailMessage("akhxxxing.com","akhtxx80@gmail.com"))
    {
        mm.Subject = "RDLC Report PDF example";
        mm.Body = "RDLC Report PDF example";
        mm.Attachments.Add(new Attachment(ExportReportToPDF(Server.MapPath("~/Excel/"), "Attendance_Status.xlsx")));
        mm.IsBodyHtml = true;
        SmtpClient smtp = new SmtpClient();
        smtp.Host = "mail.xxxxxx.com";
        smtp.EnableSsl = true;
        NetworkCredential NetworkCred = new NetworkCredential();
        NetworkCred.UserName = "axxxxg.com";
        NetworkCred.Password = "Dxxsxlxx!@";
        smtp.UseDefaultCredentials = false;
        smtp.EnableSsl = false;
        smtp.Credentials = NetworkCred;
        smtp.Port = 25;
        smtp.Send(mm);
    }
 
}
    private string ExportReportToPDF(string path, string reportName)
    {
        Warning[] warnings;
        string[] streamids;
        string mimeType;
        string encoding;
        string filenameExtension;
        byte[] bytes = ReportViewer1.LocalReport.Render("Excel", null, out mimeType, out encoding, out filenameExtension, out streamids, out warnings);
        string filename = path + reportName;
        using (var fs = new System.IO.FileStream(filename, System.IO.FileMode.Create))
        {
            fs.Write(bytes, 0, bytes.Length);
            fs.Close();
        }
 
        return filename;
    }
}