http://mannpandey.blogspot.com/2009/06/writing-excel-file-with-data-set.html

      string strConnstr = "Server=172.16.0.42;Database = dbEBSCONew;User id=gpts;password=gpts;";
             SqlConnection con = new SqlConnection(strConnstr);
             con.Open();

             string strQuery;

            Microsoft.Office.Interop.Excel.Application sXL = new Microsoft.Office.Interop.Excel.Application();
            Microsoft.Office.Interop.Excel.Workbook workBook = null;
            Microsoft.Office.Interop.Excel.Sheets sheets = null;
            Microsoft.Office.Interop.Excel.Worksheet workSheet = null;

            //Opening the Record file
            workBook = sXL.Workbooks.Open("D:\\Customlookupsheet", 0, false, 5, "", "", true, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);
            sheets = workBook.Worksheets;
            workSheet = (Microsoft.Office.Interop.Excel.Worksheet)sheets.get_Item("Occupation");
            int rowIndex = 3;

            toolStripProgressBar1.Minimum = 0;
            toolStripProgressBar1.Maximum = workSheet.UsedRange.Rows.Count;
            while (rowIndex <= workSheet.UsedRange.Rows.Count)
            {
                Microsoft.Office.Interop.Excel.Range rngParam = workSheet.get_Range("A" + rowIndex.ToString(), "A" + rowIndex.ToString());
                string strParam = Convert.ToString(rngParam.Cells.Value2);

                Microsoft.Office.Interop.Excel.Range rngParam1 = workSheet.get_Range("B" + rowIndex.ToString(), "B" + rowIndex.ToString());
                string strParam1 = Convert.ToString(rngParam1.Cells.Value2);

                strQuery = "Insert into tbOccupation values('" + strParam + "','" + strParam1 + "')";

                int x = SqlHelper.ExecuteNonQuery(con, CommandType.Text, strQuery);
                rowIndex += 1;
                toolStripProgressBar1.PerformStep();
            }