// имитация данных
        var t = new DataTable();
        t.Columns.Add("STR1", typeof(string));
        t.Columns.Add("STR2", typeof(string));
        t.Columns.Add("NUM1", typeof(int));

        for(int i=0; i<100; i++)
        {
            t.Rows.Add(string.Format("String#{0}", i), string.Format("---{0}---", i), i);
        }

        var filename = Path.GetTempFileName()+ ".xlsx";
        File.WriteAllBytes(filename, Resources.res.TemplateForExcelExport_grid);

        OleDbConnection connection = null;
        OleDbCommand command = null;
        string connectionString = "";
        string columns = "";
        string values = "";
        string[] columnNames = new string[t.Columns.Count];
        for (int i = 0; i < t.Columns.Count; i++) columnNames[i] = string.Format("F{0}", i+1);

        string sheetName = "data$"; // этот пустой лист уже есть в xls-шаблоне
        try
        {

            connectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + filename + ";Extended Properties="Excel 12.0 Xml; HDR=NO";";
            int iCount = 0;

            using (connection = new OleDbConnection(connectionString))
            {

                connection.Open();
                var colCount = 1;// columnNames.Length; - количесвто добавляемых колонок
                columns = "";
                for (int index = 0; index < colCount; index++)
                    columns += index==0 ? "[" + columnNames[index] + "]" : ", [" + columnNames[index] + "]";

                var rows =  t.Rows.Count;
                for (int irow = 0; irow < rows; irow++)
                {
                    var theValues = t.Rows[irow].ItemArray;
                    values = "";
                    for (int index = 0; index < colCount;index++)
                    {
                        var v = Convert.ToString(theValues[index]);

                        values += (index == 0) ? "'" + Regex.Replace(v, @"t|n|r", """) + "'" : ", '" + Regex.Replace(v, @"t|n|r", "") + "'";
                    }

                    using (command = connection.CreateCommand())
                    {
                        command.CommandText = string.Format("Insert into [" + sheetName + "] ({0}) values({1})", columns, values);
                        iCount += command.ExecuteNonQuery();
                    }
                }
            }

            // запускаем Excel
            Messages.InformationMessage(iCount.ToString());
            Process process = new Process();
            process.StartInfo = new ProcessStartInfo("excel", filename);
            process.Start();
        }
        catch (Exception ex)
        {

            Messages.ExclamationMessage(ex.Message, "Error");

        }