private void btnUpdate_Click(object sender, EventArgs e)
        {
            Lecture lecture = new Lecture();

            lecture.L_ID = this.dgvLecture.CurrentRow.Cells[0].Value.ToString();
            if (lecture.L_ID.Length <= 0)
            {
                return;
            }

            if (this.dgvLecture.CurrentRow.Cells[1].Value is null)
            {
                this.dgvLecture.CurrentRow.Cells[1].Value = "";
            }
            lecture.L_name = this.txtLecturename.Text.Trim();

            if (this.dgvLecture.CurrentRow.Cells[2].Value is null)
            {
                this.dgvLecture.CurrentRow.Cells[2].Value = "";
            }
            lecture.L_fullname = this.txtFullname.Text.Trim();
            if (this.dgvLecture.CurrentRow.Cells[3].Value is null)
            {
                this.dgvLecture.CurrentRow.Cells[3].Value = "";
            }
            lecture.L_department = this.cmbDepartment.Text.Trim();
            if (this.dgvLecture.CurrentRow.Cells[4].Value is null)
            {
                this.dgvLecture.CurrentRow.Cells[4].Value = "";
            }
            lecture.L_gender = this.cmbGender.Text.Trim();
            if (this.dgvLecture.CurrentRow.Cells[5].Value is null)
            {
                this.dgvLecture.CurrentRow.Cells[5].Value = "";
            }
            lecture.L_birthday = this.dateTimeBirthday.Value;
            if (this.dgvLecture.CurrentRow.Cells[6].Value is null)
            {
                this.dgvLecture.CurrentRow.Cells[6].Value = "";
            }
            lecture.L_phone = this.txtPhone.Text.Trim();
            if (this.dgvLecture.CurrentRow.Cells[7].Value is null)
            {
                this.dgvLecture.CurrentRow.Cells[7].Value = "";
            }
            lecture.L_email = this.txtEmail.Text.Trim();
            if (LectureController.UpdateLecture(lecture) == false)
            {
                MessageBox.Show("Cannot update!!!");
            }
            else
            {
                MessageBox.Show("Update success", "Note", MessageBoxButtons.OK);
                BindingSource source = new BindingSource();
                source.DataSource          = LectureController.getAllLecture();
                this.dgvLecture.DataSource = source;
            }
        }