主题：援助之手

打开窗口,在文本框输入"湖北省",按"确定"按钮,不会增加"湖北省",请帮我解决一下.

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点击浏览该文件:管理项目2.table

dim trv as winform.treeview=e.form.controls("tv1") dim nd as winform.treenode=trv.selectednode dim pnd as winform.treenode=trv.selectednode.ParentNode dim ppnd as winform.treenode=trv.selectednode.ParentNode.ParentNode Dim txt As WinForm.TextBox = e.Form.Controls("TB1") dim dr as datarow Dim Value As Integer=trv.selectednode.Level Select Case Value     Case 0        dr=datatables("jg").find("sheng = '" & txt.value & "'")        if dr is nothing then            dr=datatables("jg").addnew()            dr("sheng") = txt.value            trv.nodes.add(txt.value,txt.value)        end if    Case 1        if nd is nothing then            return        end if        dr=datatables("jg").find("xian= '" & nd.text & "' and xian= '" & txt.value & "'")        if dr is nothing then            dr=datatables("jg").addnew()            dr("sheng")=pnd.text            dr("xian")=txt.value            nd.nodes.add(txt.value,txt.value)        end if     case 2      if nd is nothing then            return        end if        dr=datatables("jg").find("xiang= '" & nd.text & "' and xiang= '" & txt.value & "'")        if dr is nothing then            dr=datatables("jg").addnew()            dr("sheng")=ppnd.text            dr("xian")=pnd.text            dr("xiang")=txt.value            nd.nodes.add(txt.value,txt.value)        end if End Select 上述代码如果不删除"dim ppnd as winform.treenode=trv.selectednode.ParentNode.ParentNode"代码,则不同增加省份,如果删除就可以增加省份,是什么原因?