private void cbb_MaSV_SelectedIndexChanged(object sender, EventArgs e)
        {
            int    rowIndex    = cbb_StudentCode.SelectedIndex;
            String studentCode = cbb_StudentCode.Text;

            dgv_View.DataSource = QLSVienDAO.GetStudentInformationByStudentCode(studentCode).Tables[0];

            DataRow selectedRow = dsStudent.Tables[0].Rows[rowIndex];

            txt_StudentInfo.Text = selectedRow["HO"] + " " + selectedRow["TEN"] + "; " + selectedRow["NGAYSINH"] + "; " + selectedRow["GIOITINH"] + "; " + selectedRow["MAKH"];
        }
        public Form1()
        {
            InitializeComponent();



            //Load student information
            try
            {
                //load student information(HO, TEN, NGAYSINH, NAM, MAKH) on dsStudent
                dsStudent = QLSVienDAO.GetStudentInformation();

                //display and set value on combobox
                cbb_StudentCode.DataSource    = dsStudent.Tables[0];
                cbb_StudentCode.DisplayMember = "MASV";
                cbb_StudentCode.ValueMember   = "MASV";



                // load first student information(HO, TEN, NGAYSINH, NAM, MAKH) by first code in cbb_StudentCode
                DataRow firstRow = dsStudent.Tables[0].Rows[0];
                txt_StudentInfo.Text = firstRow["HO"] + " " + firstRow["TEN"] + "; " + firstRow["NGAYSINH"] + "; " + firstRow["GIOITINH"] + "; " + firstRow["MAKH"];


                //load student information
                String studentCode = firstRow["MASV"].ToString();
                dgv_View.DataSource = QLSVienDAO.GetStudentInformationByStudentCode(studentCode).Tables[0];

                //set width size column
                dgv_View.Columns[0].Width = 150;
                dgv_View.Columns[1].Width = 300;
                dgv_View.Columns[2].Width = 100;
            }
            catch (Exception)
            {
                MessageBox.Show("Load data error!");
            }
        }