asp.net tree is used to display data that is organized according to a tree structure, such as a file system in a computer (a resource manager in Windows), a corporate or corporate structure, and so on. We know that under Windows VB, PB, Delphi and other tools provide a very powerful tree control TreeView, using the TreeView control can easily develop a tree diagram. However, it's not easy to implement tree on a Web page, and now use Microsoft's Internet Explorer WebControls in ASP.net, which makes tree development on Web pages as convenient, powerful, and even flexible as it is under Windows.
This paper introduces the method of developing tree using Internet Explorer WebControls, because the tree structure is more complicated, so it is often not known how to start. The author combined with the recent application manager for the company to write a specific example, the detailed description of the Internet Explorer in the asp.net under the use of WebControls with the database, the realization of arbitrary multi-level data display, easy to increase, Modify, delete, move operations. I hope that through the elaboration of this example to achieve the effect of a good, and colleagues to communicate with each other, and common progress.
Internet Explorer WebControls is not in Vs.net's standard server control and will be downloaded at Microsoft's site by downloading the address:
For the first time after installation, right-click the Toolbox customize Toolbox ... Micosoft.Web.UI.WebControls.Treeview is selected after the →.net Framework components is found, so the TreeView control appears in the Toolbox.
First, the establishment of trees
The specific method is: Create a database, design tree diagram information table tree_info, including Nodeid, ParentID, nodename, Adderss, icon fields, other fields based on the actual business, the node name nodename will be displayed on the tree control node , the Nodeid field holds a unique identification number for the node, ParentID represents the parent node number of the current node, and the identification number consists of a "linked list" that records the structure of the nodes on the tree. Design a Web form on which to place the TreeView control.
Private Sub CreateDataSet () ' Set up data set
Dim myconn as New SqlConnection ()
Dim myCMD as New SqlCommand ("Select Nodeid,nodename,parentid,address,icon from Tree_info", myconn)
The basic idea of achievement is: To start a recursive call from the root node to display the subtree
Private Sub Page_Load (ByVal sender as System.Object, ByVal e as System.EventArgs) Handles MyBase.Load
CreateDataSet ()
Intitree (treeview1.nodes, 0)
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-1). Nodes, IntId)
Next
End Sub
Add and Delete tree nodes
Simply add, delete, and modify nodes in the TreeView only with the Add, remove, and other methods of the nodes attribute, What is noteworthy is the difference between the nodes set of the TreeView in the Vs.net and the VS6.0, the VS6.0 is a large set, and vs.net is the nodes attribute under each node in the hierarchy. Adding, deleting, and modifying tree nodes are very different than VS6.0, especially when you delete them.
Private Sub Butadd_click (ByVal sender as System.Object, ByVal e as System.EventArgs) Handles butadd.click ' Add child nodes under selected node
Private Function Getndcol (ByVal idx as String) as TreeNodeCollection
' Gets the nodes collection of the parent node of the selected node
Dim cnt As Integer, I As Integer
Dim Tmpnds as TreeNodeCollection
Dim Idxs () as String
IDXS = Split (idx, ".")
CNT = UBound (IDXS)
If cnt = 0 Then
Tmpnds = Treeview1.nodes
Else
Tmpnds = Treeview1.nodes (CInt (IDXS (0))). Nodes
For i = 1 to Cnt-1
Tmpnds = Tmpnds (CInt (IDXS (i))). Nodes
Next
End If
Return Tmpnds
End Function
Third, modify, Move tree node
Because the server control does not support mouse drag events, you cannot drag the mobile node in the same way as a Windows program, by selecting the parent node. The move is done by deleting it in the original location and adding it to the new location, so be careful to save the node information before deleting it.
Private Sub Treeview1_selectedindexchange (ByVal sender as Object, ByVal e As Microsoft.Web.UI.WebControls.TreeViewSelectEventArgs) Handles Treeview1.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 (0) ("node_descript") = Me.TextBox1.Text
DV (0) ("address") = Me.TextBox2.Text
DV (0) ("TARGET") = Me.TextBox3.Text
DV (0) ("ICON") = Me.TextBox4.Text
If DV (0) ("ParentID"). ToString <> Me.DropDownList1.SelectedItem.Value Then
' Move the node
DV (0) ("parent_name") = Me.DropDownList1.SelectedItem.Value
If Me.DropDownList1.SelectedItem.Value = "ROOT" Then
Tmpnds = Treeview1.nodes
Else
Tmpnds = Fromidtonode (Me.DropDownList1.SelectedItem.Value, Treeview1.nodes). Nodes ' The Nodes collection of the new parent node
Private Function Fromidtonode (ByVal ID as String, ByVal Nds as TreeNodeCollection) as TreeNode
' Lookup node by keyword
Dim I as Integer
Dim TMPND as TreeNode, tmpNd1 as TreeNode
For all tmpnd in Nds
If tmpnd.id = ID Then
Return TMPND
Exit Function
End If
TMPND1 = Fromidtonode (ID, Tmpnd.nodes)
If not (TmpNd1 are nothing) Then
Return TMPND1
Exit Function
End If
Next
Return Nothing
End Function
Iv. concluding remarks
The above describes the basic method of tree-like display in asp.net, and how to modify the database data while maintaining the tree nodes (adding, deleting, modifying, moving). Due to space limitations, the author here only the basic ideas and procedures and key steps are introduced, not listed in detail the source code, the reader can be perfected. Need detailed source code can contact me, this program in vs.net, SQL Server, Windows 2000, IIS5.0 debugging pass.
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