private void t_submit_result_Click(object sender, EventArgs e)
        {
            try
            {
                OpenFileDialog ope = new OpenFileDialog();
                ope.Filter = "Excel Files|*.xls;*.xlsx;*.xlsm*";
                if (ope.ShowDialog() == DialogResult.Cancel)
                {
                    return;
                }

                FileStream       stream      = new FileStream(ope.FileName, FileMode.Open);
                IExcelDataReader excelReader = ExcelReaderFactory.CreateOpenXmlReader(stream);
                DataSet          result      = excelReader.AsDataSet();

                DataClasses1DataContext conn = new DataClasses1DataContext();
                foreach (DataTable table in result.Tables)
                {
                    foreach (DataRow dr in table.Rows)
                    {
                        marks_tbl addtable = new marks_tbl()
                        {
                            student_id        = Convert.ToString(dr[0]),
                            quiz              = Convert.ToInt32(dr[1]),
                            class_performance = Convert.ToInt32(dr[2]),
                            final             = Convert.ToInt32(dr[3]),
                            total             = Convert.ToInt32(dr[4]),
                            grade             = Convert.ToString(dr[5]),
                        };
                        conn.marks_tbls.InsertOnSubmit(addtable);
                    }
                }
                //String stringconn = "provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + textBox1.Text + ";Extended Properties=\"Excel 8.0;HDR=Yes;\";
                conn.SubmitChanges();
                excelReader.Close();
                stream.Close();
                MessageBox.Show("successfull");
            }
            catch (Exception ex)
            {
                //sqlConnection.Close();
                MessageBox.Show("This file is already in the database!");
            }
        }
 partial void Updatemarks_tbl(marks_tbl instance);
 partial void Deletemarks_tbl(marks_tbl instance);
 partial void Insertmarks_tbl(marks_tbl instance);