C# Import ข้อมูลใน excel ขึ้น datatable แล้วเอา datatable เข้า database ภาษาไทยเป็น ??

private void btnOpen_Click(object sender, EventArgs e)
        {
            OpenFileDialog openfile = new OpenFileDialog();
            openfile.Title = "Select file";
            openfile.Filter = "Excel Sheet(*.xls,*.xlsx)|*.xls;*.xlsx|All Files(*.*)|*.*";
            openfile.FilterIndex = 1;
            openfile.RestoreDirectory = true;
            if (openfile.ShowDialog() == DialogResult.OK)
            {
                textBox1.Text = openfile.FileName;
                System.Data.DataTable dtb = ConvertToDataTable(textBox1.Text);
                dataGridView1.DataSource = dtb;
            }
        }

public System.Data.DataTable ConvertToDataTable(string path)
        {
            try
            {
                object rowIndex = 1;
                dt = new System.Data.DataTable();
                DataRow row;
                Microsoft.Office.Interop.Excel.Application app = new Microsoft.Office.Interop.Excel.Application();
                
                Microsoft.Office.Interop.Excel.Workbook workBook = app.Workbooks.Open(path, 0, true, 5, "", "", true,
                Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);
                Microsoft.Office.Interop.Excel.Worksheet workSheet = (Microsoft.Office.Interop.Excel.Worksheet)workBook.ActiveSheet;
               

                int temp = 1;
                while (((Microsoft.Office.Interop.Excel.Range)workSheet.Cells[rowIndex, temp]).Value2 != null)
                {
                    dt.Columns.Add(Convert.ToString(((Microsoft.Office.Interop.Excel.Range)workSheet.Cells[rowIndex, temp]).Value2));
                    temp++;
                }
                rowIndex = Convert.ToInt32(rowIndex) + 1;
                int columnCount = temp;
                temp = 1;
                while (((Microsoft.Office.Interop.Excel.Range)workSheet.Cells[rowIndex, temp]).Value2 != null)
                {
                    row = dt.NewRow();
                    for (int i = 1; i < columnCount; i++)
                    {
                        row[i - 1] = Convert.ToString(((Microsoft.Office.Interop.Excel.Range)workSheet.Cells[rowIndex, i]).Value2);
                    }
                    dt.Rows.Add(row);
                    rowIndex = Convert.ToInt32(rowIndex) + 1;
                    temp = 1;
                }
                app.Workbooks.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error:" + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            return dt;
        }

private void btnImportDB_Click(object sender, EventArgs e)
        {
            if(dt!=null)
            {
                try
                {
                    cn.ConnectionString = connSt;
                    cmd.Connection = cn;
                    cn.Open();

                    cmd.CommandText = "delete from info";
                    cmd.ExecuteNonQuery();

                    for (int i = 0; i < dt.Rows.Count; i++)
                    {
                        cmd.CommandText = "insert into info (idst,name,sname,sex,class,room,number) values ('" + dt.Rows[i]["idst"].ToString()
                            + "','" + dt.Rows[i]["name"].ToString() + "','" + dt.Rows[i]["sname"].ToString() + "','" + dt.Rows[i]["sex"].ToString()
                            + "','" + dt.Rows[i]["class"].ToString() + "','" + dt.Rows[i]["room"].ToString() + "','" +
                            dt.Rows[i]["number"].ToString() + "')";
                        cmd.ExecuteNonQuery();
                    }
                    MessageBox.Show("Success!", "Result", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
                finally
                {
                    cn.Close();
                }
            }
        }