private void buttonAdd_Click(object sender, EventArgs e)
 {
     if (textBoxSection.Text == "")
     {
         ProcessInvalid(labelSection);
         MessageBox.Show("Section name can't be empty", "", MessageBoxButtons.OK, MessageBoxIcon.Error);
     }
     else if (comboBoxTeacher.Text == "--Select--")
     {
         ProcessInvalid(labelTeacher);
         MessageBox.Show("Must Select a Class Teacher", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
     }
     else if (CheckSectionExists(textBoxSection.Text))
     {
         ProcessInvalid(labelSection);
         MessageBox.Show("Section already exists", "", MessageBoxButtons.OK, MessageBoxIcon.Error);
     }
     else
     {
         var classSec = new ClassSection
         {
             ClassId        = selectClassId,
             SectionName    = textBoxSection.Text,
             IsActive       = checkBoxIsActive.Checked,
             ClassTeacherId = (int)comboBoxTeacher.SelectedValue
         };
         if (_settingService.AddClassSection(classSec))
         {
             MessageBox.Show("Data Saved Successfully!", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information);
             ProcessValid(labelSection);
             ProcessValid(labelTeacher);
             gridViewSelectedId = classSec.ClassSectionId.ToString();
             LoadDataSection(_settingService.GetClassSectionList(classSec.ClassId));
             dataGridViewSection.Refresh();
         }
         else
         {
             MessageBox.Show("error");
         }
     }
 }