知识大全 ASP.NET中树形图的实现

Posted 2022-07-16 知

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　　树形图用于显示按照树形结构进行组织的数据其用途比较广泛如计算机中的文件系统(Windows中的资源管理器) 企业或公司的组成结构等我们知道在Windows下VB PB Delphi等工具提供了一个功能很强的树型控件TreeView 利用Treeview控件可以方便地开发树形图然而在网页上实现树形图就不那么容易了现在在ASP NET中利用微软提供的Internet Explorer WebControls它使得网页上的树形图开发与在Windows下一样的方便一样的功能强大甚至更灵活

　　本文介绍用Internet Explorer WebControls开发树形图的方法由于树形图结构较复杂使用起来常不知如何下手笔者结合最近刚为公司用ASP NET编写的应用程序管理器这一具体实例详细阐述在ASP NET下如何将Internet Explorer WebControls的使用与数据库联系起来实现数据分任意多层显示方便地进行增加修改删除移动操作笔者希望通过对该实例的阐述达到抛砖引玉的效果与各位同仁相互交流共同进步

　　Internet Explorer WebControls不在VS NET的标准Server Control中要到微软的站点上下载下载地址是 //msdn microsoft /downloads/samples/internet/default asp？url=/Downloads/samples/Internet/ASP_DOT_NET_ServerControls/WebControls/default asp 下载安装后第一次使用时要右击工具箱Customize Toolbox…→ NET Framework Components中找到Micosoft Web UI WebControls Treeview后选中这样Treeview控件就出现在工具箱中了

　　一树的建立

　　具体方法是创建一个数据库设计树图信息表TREE_INFO 包含NODEID PARENTID NODENAME ADDERSS ICON字段其它字段根据实际业务而定节点名称NODENAME将在树型控件的节点上显示 NODEID字段保存节点的唯一标识号 PARENTID表示当前节点的父节点号标识号组成了一个链表记录了树上节点的结构设计一个Web窗体其上放置TreeView控件

Private Sub CreateDataSet() 建立数据集 Dim myConn As New SqlConnection() Dim myCmd As New SqlCommand( select NODEID NODENAME PARENTID ADDRESS ICON from Tree_info myConn) Dim myDataAdapter As New SqlDataAdapter() myConn ConnectionString = Application( connectstring ) myCmd CommandText = myCmd Connection = myConn myDataAdapter SelectCommand = myCmd myDataAdapter Fill(ds tree ) End Sub

　　建树的基本思路是从根节点开始递归调用显示子树

Private Sub Page_Load(ByVal sender As System Object ByVal e As System EventArgs) Handles MyBase Load CreateDataSet() intiTree(TreeView Nodes ) End Sub Private Sub intiTree(ByRef Nds As TreeNodeCollection ByVal parentId As Integer) Dim dv As New DataView() Dim drv As DataRowView Dim tmpNd As TreeNode Dim intId As Integer dv Table = ds Tables( tree ) dv RowFilter = PARENTID= & parentId & For Each drv In dv tmpNd = New TreeNode() strId = drv( NODE_ID ) tmpNd ID = strId tmpNd Text = drv( NODE_NAME ) tmpNd ImageUrl = drv( ICON ) ToString Nds Add(tmpNd) intiTree(Nds(Nds Count ) Nodes intId) Next End Sub 　　二增加删除树节点

　　单纯在Treeview 上增加删除修改节点只需用Nodes属性的Add Remove 等方法即可值得注意的地方是VS NET中Treeview的Nodes集合与VS 中的区别 VS 中的是一个大的集合而VS NET中的是分层的每个Node下都有Nodes属性增加删除修改树节点时与VS 相比有很大差别特别是删除时

Private Sub ButAdd_Click(ByVal sender As System Object ByVal e As System EventArgs) Handles ButAdd Click 在选定的节点下添加子节点 Dim tmpNd As New TreeNode() NdSel As TreeNode tmpNd ID = GetNewId() NdSel = TreeView GetNodeFromIndex(TreeView SelectedNodeIndex) 选中的节点 tmpNd Text = 新节点 NdSel Nodes Add(tmpNd) Dim myRow As DataRow myRow = ds Tables( tree ) NewRow() myRow( NODE_NAME ) = tmpNd ID myRow( NODE_DESCRIPT ) = 新节点 & tmpNd ID & _ & NdSel ID myRow( PARENT_NAME ) = NdSel ID ds Tables( tree ) Rows Add(myRow) End Sub Private Sub ButDele_Click(ByVal sender As Object ByVal e As System EventArgs) Handles ButDele Click 删除选中的节点 Dim idx As String = TreeView SelectedNodeIndex() GetNdCol(idx) Remove(TreeView GetNodeFromIndex(idx)) Dim dv As New DataView() recNo As Integer dv Table = ds Tables( tree ) dv RowFilter= NODEID= & NdId dv Delete( ) End Sub Private Function GetNdCol(ByVal idx As String) As TreeNodeCollection 获得选中节点的父节点的Nodes集合 Dim cnt As Integer i As Integer Dim tmpNds As TreeNodeCollection Dim idxs() As String idxs = Split(idx ) cnt = UBound(idxs) If cnt = Then tmpNds = TreeView Nodes Else tmpNds = TreeView Nodes(CInt(idxs( ))) Nodes For i = To cnt tmpNds = tmpNds(CInt(idxs(i))) Nodes Next End If Return tmpNds End Function 　　三修改移动树节点

　　由于服务器控件不支持鼠标拖动事件所以不能象Windows程序那样通过拖动移动节点这里是通过选择父节点的方式移动是通过在原位置删除新位置添加实现的要注意在删除时先保存节点信息

Private Sub TreeView _SelectedIndexChange(ByVal sender As Object ByVal e As Microsoft Web UI WebControls TreeViewSelectEventArgs) Handles TreeView SelectedIndexChange Dim dv As New DataView() dv Table = ds Tables( tree ) Dim tmpNd As TreeNode = TreeNdSel(e OldNode) tmpNds As TreeNodeCollection dv RowFilter= NODEID= & tmpNd ID dv( )( NODE_DESCRIPT ) = Me TextBox Text dv( )( ADDRESS ) = Me TextBox Text dv( )( TARGET ) = Me TextBox Text dv( )( ICON ) = Me TextBox Text If dv( )( PARENTID ) ToString <> Me DropDownList SelectedItem Value Then 移动节点 dv( )( PARENT_NAME ) = Me DropDownList SelectedItem Value If Me DropDownList SelectedItem Value = ROOT Then tmpNds = TreeView Nodes Else tmpNds = FromIdToNode(Me DropDownList SelectedItem Value TreeView Nodes) Nodes 新的父节点的Nodes集合 End If GetNdCol(e OldNode) Remove(tmpNd) tmpNds Add(tmpNd) End If tmpNd Text = Me TextBox Text tmpNd ImageUrl = Me TextBox Text tmpNd = TreeView GetNodeFromIndex(TreeView SelectedNodeIndex) dv RowFilter= NODEID= & tmpNd ID Me TextBox Text = dv( )( NODENAME ) ToString Me TextBox Text = dv( )( ADDRESS ) ToString Me TextBox Text = dv( )( TARGET ) ToString Me TextBox Text = dv( )( ICON ) ToString End Sub Private Function FromIdToNode(ByVal ID As String ByVal Nds As TreeNodeCollection) As TreeNode 由关键字查找节点 Dim i As Integer Dim tmpNd As TreeNode tmpNd As TreeNode For Each tmpNd In Nds If tmpNd ID = ID Then Return tmpNd Exit Function End If tmpNd = FromIdToNode(ID tmpNd Nodes) If Not (tmpNd Is Nothing) Then Return tmpNd Exit Function End If Next Return Nothing End Function

　　四结束语

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