// how to know which text you choice or edit
        private void button1_Click(object sender, System.EventArgs e)
        {
            int    FindIndex;
            string strMsg = "目前你的选择是:";

            FindIndex = MulQuery.FindStringExact(MulQuery.Text);
            if (FindIndex < 0)
            {
                MulQuery.Items.Add(MulQuery.Text);
                strMsg += MulQuery.Text;
            }
            else
            {
                strMsg += MulQuery.SelectedItem.ToString();
            }

            MessageBox.Show(strMsg);
        }
 //Part 2: ComboBox Test
 //How to add string to the combobox
 private void button2_Click(object sender, System.EventArgs e)
 {
     if (MulQuery.FindString("有教授参与授课的所有课程") < 0)
     {
         MulQuery.BeginUpdate();
         MulQuery.Items.Add("有教授参与授课的所有课程");
         MulQuery.Items.Add("有副教授参与授课的所有课程");
         MulQuery.Items.Add("所有选择教授所授课程的学生");
         MulQuery.Items.Add("王心怡老师的所有学生");
         MulQuery.Items.Add("所有有课程冲突的学生");
         MulQuery.EndUpdate();
     }
     if (MulQuery.FindString(MulQuery.Text) < 0)
     {
         MulQuery.BeginUpdate();
         MulQuery.Items.Add(MulQuery.Text);
         MulQuery.EndUpdate();
     }
     else
     {
         MessageBox.Show(MulQuery.Text + "已经存在");
     }
 }