class Program
    {
        static string attfile = @"C:\Excel_temp\ext\null.xlsx";
        static Excel.Application excelApp = new Excel.Application();
        static Excel.Workbook excelBook;
        static int rowcount;
        static string prewmonth;
 
        static void Main()
        {
            exceling();
            if (rowcount > 1)
            {
                mailing();
            }
        }
 
        public static int LastRowCell()
        {
            int lastrow = excelApp.Sheets[1].Cells.SpecialCells(Excel.XlCellType.xlCellTypeLastCell).Row;
            for (int i = lastrow; i >= 1; i--)
            {
                if (excelApp.Cells[i, 2].Value != null)  // 2 - вторая по счету колонка
                {
                    rowcount = i;
                    break;
                }
            }
 
            return rowcount;
        }
 
        static void exceling()
        {
            excelApp.Visible = false;
            excelBook = excelApp.Workbooks.Open(attfile);
 
            foreach (Excel.WorkbookConnection cnn in excelBook.Connections)
            {
                cnn.OLEDBConnection.BackgroundQuery = false;
            }
 
            excelBook.RefreshAll();
            LastRowCell();
            excelBook.Save();
            excelBook.Close(0);
            excelApp.Quit();
 
        }
 
        static void mailing()
        {
            prewmonth = DateTime.Now.AddMonths(-1).ToString("MMMM");
            SmtpClient smtp = new SmtpClient();
            MailMessage message = new MailMessage();
            smtp.EnableSsl = true;
            smtp.Host = "smtp.mail.ru";
            smtp.Port = 587;
            Attachment file = new Attachment(attfile);
            message.Attachments.Add(file);
            try
            {
                smtp.Send(message);
            }
            catch (SmtpException)
            {
 
            }
        }
    }