两级关键词，复选框级联选择。借助hiddenField

1. 级联复选框
   关键词分两级，子级选中时父级自动选中；父级取消选中时子级自动取消选中；
   由于checkboxlist的SelectedIndexChanged事件无法确定当前改变选择的复选框。因此采用HiddenField辅助完成。将改变
选择之前选中的复选框value值以逗号隔开存到里面。

2. 加载页面时初始化该值
   

 protected void Page_Load(object sender, EventArgs e)
    {
    if (Request.QueryString["id"] == null || )
            {
                this.hidCheckbox.Value = "";
            }
             if (Request.QueryString["id"] != null )
            {
            。。。。
            if (dr1["KID"].ToString().Equals(CheckBoxList_keyword.Items[i].Value.ToString()))
                        {
                            CheckBoxList_keyword.Items[i].Selected = true;
                            hidCheckbox.Value += " " + dr["KID"].ToString() + ",";
                        }

            。。。。
            }
            
    }

   
3.改变选择时进行相应的操作。
   

#region 关键词级联选择
    
    protected void CheckBoxList_keyword_SelectedIndexChanged(object sender, EventArgs e)
    {
        string sOld = this.hidCheckbox.Value;
        foreach (ListItem item in CheckBoxList_keyword.Items)
        {
            string sql = "select FirstID,KID from ServiceKey where KID='" + item.Value + "'";
            SqlDataReader dr = db.GetReader(sql);
            string ChildID = "";//子关键词
            string ParentID = "";//父关键词
             if (dr.Read())
            {
                ChildID = dr["KID"].ToString();
                ParentID = dr["FirstID"].ToString();
            }
            dr.Close();
            if (ChildID == ParentID)//当前为父关键词            {
                string childs = ",";
                if (!item.Selected && sOld.Contains(ChildID.Trim ()+","))//由选中变为不选中
                {
                    sql = "select FirstID,KID from ServiceKey where FirstID='" + item.Value + "' and 
FirstID!=KID";
                    dr = db.GetReader(sql);
                    while (dr.Read())
                    {
                        childs += dr["KID"].ToString() + ",";
                    }
                    dr.Close();
                    if (childs != ",")
                    {
                        foreach (ListItem child in CheckBoxList_keyword.Items)
                        {
                            if (childs.Contains (","+child .Value .Trim ()+","))
                            {
                                child.Selected = false;//子关键词自动变为未选中
                            }
                        }
                    }
                }
            }
            else//当獭?前°为a子哩?关?键ü词洙?
            {
                if (item.Selected&&!sOld .Contains (ChildID ))//由未选中变为选中
                {
                    foreach (ListItem parent in CheckBoxList_keyword.Items)
                    {
                        if (parent.Value.ToString() == ParentID)
                        {
                            parent.Selected = true;//父关键词自动选中                        }
                    }
                }
            }
        }
        //重新构造该字符串
        string sNew = "";
        foreach (ListItem li in CheckBoxList_keyword.Items)
        {
            if (li.Selected)
                sNew += " " + li.Value + ",";
        }
        this.hidCheckbox.Value = sNew;
    }
    #endregion