关于dropdownlist控件的问题,语言=VB
在asp.net2.0中,有三个dropdownlist控件分别对应数据库里面的系部表(department),专业表(speciality)和班级表(class),现在在page_load事件中已经联结上了系部名称字段;代码如下:
Protected   Sub   Page_Load(ByVal   sender   As   Object,   ByVal   e   As   System.EventArgs)   Handles   Me.Load
                Dim   sql   As   String
                Dim   conn   As   New   SqlConnection
                conn.ConnectionString   =   "data   source=192.168.31.199;initial   catalog=kaoqin   manager;user   id=james5;password=james5; "
                sql   =   "select   *   from   department "
                Dim   cmd   As   New   SqlCommand(sql,   conn)
                conn.Open()
                Dim   dr   As   SqlDataReader
                dr   =   cmd.ExecuteReader()
                DropDownList1.AppendDataBoundItems   =   True
                DropDownList1.Items.Add(New   ListItem( "--请选择-- ",   "-1 "))
                DropDownList1.DataSource   =   dr
                DropDownList1.DataValueField   =   "departmentNo "
                DropDownList1.DataTextField   =   "departmentname "
                DropDownList1.DataBind()
        End   Sub
但是在dropdownload的Index_change事件中关联专业表是出了总是,老是自动刷新,而且每刷新一次,dropdownlist控件的系部和专业名称又会自动增加,请高手帮忙看一下错到哪里;不胜感激.关联字段如下:
  Protected   Sub   DropDownList1_SelectedIndexChanged(ByVal   sender   As   Object,   ByVal   e   As   System.EventArgs)   Handles   DropDownList1.SelectedIndexChanged
                Dim   sql   As   String
                Dim   conn   As   New   SqlConnection
                conn.ConnectionString   =   "data   source=192.168.31.199;initial   catalog=kaoqin   manager;user   id=james5;password=james5; "
                sql   =   "select   *   from   speciality   where   departmentNo= ' "   &   DropDownList1.SelectedValue   &   " ' "
                Dim   cmd   As   New   SqlCommand(sql,   conn)
                conn.Open()
                Dim   dr   As   SqlDataReader
                dr   =   cmd.ExecuteReader()
                DropDownList5.AppendDataBoundItems   =   True