我想用三个Gridview 分级显示(页面载入时只有Gridview1可见,Gridview2,3都不可见),比如Gridview1显示<系别> ,Gridview2显示<专业>
Gridview3显示<学生>
也就是在Gridview1上选择某个<系别>,然后Gridview2可见,
Gridview2显示Gridview1选定<系别>的所有<专业>
然后在Gridview2上选择某个<专业>,然后Gridview3可见,
Gridview3显示Gridview2选定<专业>下的所有 <学生>
  当然其中Gridview2,3的数据源 是改变它们的xpath来指定的

  Protected Sub GridView1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles GridView1.SelectedIndexChanged
        Dim currentIndex As Integer
        currentIndex = GridView1.SelectedIndex
        departmentid = CStr(GridView1.DataKeys(currentIndex).Value)
        XmlDataSource2.XPath = String.Format("/学生管理/系别[@系号=" & departmentid & "]/专业", departmentid)
        GridView2.Visible = True
    End Sub

    Protected Sub GridView2_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles GridView2.SelectedIndexChanged
        Dim currentIndex1 As Integer
        currentIndex1 = GridView2.SelectedIndex
        Dim majorid As String
        majorid = CStr(GridView2.DataKeys(currentIndex1).Value)
        XmlDataSource3.XPath = String.Format("//专业[@专业号=" & majorid & "]/*", majorid)
        GridView3.Visible = True
    End Sub

  我的问题是:  Gridview3不能显示
Gridview1 显示的是<系别>中的两个属性<系名>和<系号>,
Gridview2显示的是<专业>中的两个属性<专业名>和<专业号>  

那我怎么不能通过Gridview3 显示<学生>下的子元素啊?? ,比如<学号><姓名>

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