ComboBox的数据联动

Posted 2020-07-06 나 는 당신

tags:

篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了ComboBox的数据联动相关的知识，希望对你有一定的参考价值。

实现效果：

点击年级下拉框值时，获取科目下拉框值

一：加载年级下拉框值

GradeDAL层：

      //检索所有年级名称集合，返回的是泛型集合List<Grade>
      public List<Grade> GetAllGrade()
      {
          string sql = "select * from  Grade";
          //将sql转成内存中的一张表
          DataTable dt = SQLHelper.ExecuteDataTable(sql);
          MyTool tool = new MyTool();
          //dt转成list
          List<Grade> list = tool.DataTableToList<Grade>(dt);
          return list;
      
      
      }

GradeBLL层：

        //植入DAL层的对象
        GradeDAL gradeDal=new GradeDAL();
        public List<Grade> GetAllGrade()
        {
            return gradeDal.GetAllGrade();
        }

UI层：

  private void frmSelectResult_Load(object sender, EventArgs e)
        {
            //清空
            cboSubject.DropDownHeight = 106;

            GradeBLL gradeBll = new GradeBLL();
            //对年级下拉框绑定数据
            List<Grade> list = gradeBll.GetAllGrade();
           
            cboGrade.ValueMember = "GradeId";
            cboGrade.DisplayMember = "GradeName";
            cboGrade.DataSource = list;

           // flag = true;
        }

二：根据年级编号，去加载科目下拉框数据

1.在DAL层写一个根据年级编号获取科目集合的方法

SubjectDAL层：

   public List<Subject> GetAllSubject(int id)
       {
           string sql = "select * from Subject where GradeId=@Id";
           SqlParameter para = new SqlParameter("@Id",id);
           DataTable dt = SQLHelper.ExecuteDataTable(sql,para);
           MyTool tool = new MyTool();
           List<Subject> list= tool.DataTableToList<Subject>(dt);
           return list;
       
       }

2.Bll层做数据传递

      SubjectDAL subjectDal = new SubjectDAL();

      public List<Subject> GetAllSubject(int id)
      {
          return subjectDal.GetAllSubject(id);
      }

3.UI层下拉框选中项发生改变的事件：SelectedIndexChanged

        SubjectBLL subBll = new SubjectBLL();
        private void cboGrade_SelectedIndexChanged(object sender, EventArgs e)
        {
           // if (flag)
           // {
                int selectid = Convert.ToInt32(cboGrade.SelectedValue);
                List<Subject> list = subBll.GetAllSubject(selectid);

                cboSubject.ValueMember = "SubjectId";
                cboSubject.DisplayMember = "SubjectName";
                cboSubject.DataSource = list;
            //}
        }

注：