private void buttonUpdate_Click(object sender, EventArgs e)
        {
            List <Subject> subjects = new List <Subject>();

            foreach (var item in listBoxSubject.SelectedItems)
            {
                var     data = (SubjectViewModel)item;
                Subject sub  = new Subject {
                    SubjectId = data.SubjectId, SubjectName = data.SubjectName
                };
                subjects.Add(sub);
            }
            List <ClassSectionSubjectViewModel> csSubjectList = new List <ClassSectionSubjectViewModel>();

            if (checkBoxAllSection.Checked == true)
            {
                var csList = _settingService.GetClassSectionId(((ClassViewModel)comboBoxClass.SelectedItem).ClassId);
                foreach (var item in csList)
                {
                    var clssub = new ClassSectionSubjectViewModel
                    {
                        ClassSectionId = item.ClassSectionId,
                        SubjectList    = subjects
                    };
                    csSubjectList.Add(clssub);
                }
            }
            else
            {
                var clssub = new ClassSectionSubjectViewModel
                {
                    ClassSectionId = ((ClassSectionViewModel)comboBoxSection.SelectedItem).ClassSectionId,
                    SubjectList    = subjects
                };
                csSubjectList.Add(clssub);
            }
            if (_settingService.AssigningSubjetToClassSection(csSubjectList))
            {
                MessageBox.Show("Data Saved Successfully!", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }