ASP. NET Tree Structure

ASP. NET tree charts are used to display data organized by tree structures. They are widely used, such as file systems in computers (resource managers in Windows) and the composition structure of enterprises or companies. We know that in Windows, tools such as VB, PB, and Delphi provide a powerful tree-type control TreeView. Using the Treeview control, we can easily develop a tree chart. However, it is not so easy to implement tree embedding on the web page. NET uses the Internet Explorer WebControls provided by Microsoft to make the tree structure development on the web page as convenient as it is in Windows. The same functions are powerful and even more flexible.

This article describes how to use Internet Explorer WebControls to develop an ASP. NET tree structure. Due to the complex structure of the tree structure, I often do not know how to use it. I have recently used ASP for my company. the specific example of the Application Manager compiled by. NET is described in detail in ASP. NET, how to associate the use of Internet Explorer WebControls with the database to display data in multiple layers, so as to conveniently add, modify, delete, and move data. I hope that through the elaboration of this instance, I will bring you a better result, communicate with colleagues, and make progress together.

I. Tree Creation

The specific method is to create a database and design the TREE_INFO table of the tree chart, which contains the NODEID, PARENTID, NODENAME, ADDERSS, and ICON fields. Other fields are determined based on the actual business, the node name NODENAME is displayed on the node of the tree control. The NODEID field stores the unique ID of the node. PARENTID indicates the parent node number of the current node. the ID number forms a "linked list ", the structure of the nodes on the tree is recorded. Design a Web form and place the TreeView control on it.

 
 

  
  
Private Sub CreateDataSet () 'create a dataset
  
  
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
 
 

The basic idea of building a tree is to recursively call the display subtree from the root node.

 
 

  
  
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 
 
 

2. add and delete Tree nodes

To Add, delete, or modify a node in a Treeview, you only need to use the Add, Remove, and other methods of the Nodes attribute. It is worth noting that. in NET, the Nodes set of Treeview is different from that in VS6.0. VS6.0 is a large set, while. in. NET, each Node in the hierarchy has the Nodes attribute. The addition, deletion, and modification of Tree nodes are significantly different from those of VS6.0, especially when a tree node is deleted.
Private Sub ButAdd_Click (ByVal sender As System. Object, ByVal e As System. EventArgs) Handles ButAdd. click' Add a subnode under the selected node

 
 

  
  
Dim tmpNd As New TreeNode (), NdSel As TreeNode
  
  
TmpNd. ID=GetNewId()
  
  
NdSel=TreeView1. GetNodeFromIndex (TreeView1.SelectedNodeIndex) 'selected node
  
  
TmpNd. Text="New node" 
  
  
NdSel. Nodes. Add (tmpNd)
  
  
Dim myRow As DataRow
  
  
MyRow=Ds. Tables ("tree"). NewRow ()
  
  
MyRow ("NODE_NAME") = tmpNd. ID
  
  
MyRow ("NODE_DESCRIPT") = "new node" & 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' Delete the selected node
  
  
Dim idxString=TreeView1. SelectedNodeIndex ()
  
  
GetNdCol (idx). Remove (TreeView1.GetNodeFromIndex (idx ))
  
  
Dim dv As New DataView (), recNo As Integer
  
  
Dv. Table=Ds. Tables ("tree ")
  
  
Dv. RowFilter="NODEID ="& NdId
  
  
Dv. Delete (0)
  
  
End Sub
  
  
Private Function GetNdCol (ByVal idx As String) As TreeNodeCollection
  
  
'Obtain the Nodes set 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)
  
  
IfCnt=0Then
  
  
TmpNds=TreeView1. Nodes
  
  
Else
  
  
TmpNds=TreeView1. Nodes (CInt (idxs (0). Nodes
  
  
ForI=1To cnt-1
  
  
TmpNdsTmpNds= TmpNds (CInt (idxs (I). Nodes
  
  
Next
  
  
End If
  
  
Return tmpNds
  
  
End Function
 
 

3. Modify and move a tree node

Because the server control does not support mouse drag, you cannot drag a node like a Windows program. Here, you can select a parent node. Moving is implemented by deleting the original location and adding a new location. Note that the node information is saved before deletion.

 
 

  
  
Private Sub treeviewincluselectedindexchange (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 tmpNdTreeNode=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 a node
  
  
Dv (0) ("PARENT_NAME") = Me. DropDownList1.SelectedItem. Value
  
  
IfMe. DropDownList1.SelectedItem. Value="ROOT"Then
  
  
TmpNds=TreeView1. Nodes
  
  
Else
  
  
TmpNds=FromIdToNode(Me. DropDownList1.SelectedItem. Value,
TreeView1.Nodes). Nodes the Nodes set of the new parent node
  
  
End If
  
  
GetNdCol (e. OldNode). Remove (tmpNd)
  
  
TmpNds. Add (tmpNd)
  
  
End If
  
  
TmpNd. Text=Me. TextBox1.Text
  
  
TmpNd. ImageUrl=Me. TextBox4.Text
  
  
TmpNd=TreeView1. GetNodeFromIndex (TreeView1.SelectedNodeIndex)
  
  
Dv. RowFilter="NODEID ="& TmpNd. ID
  
  
Me. TextBox1.Text=Dv(0) ("NODENAME"). ToString
  
  
Me. TextBox2.Text=Dv(0) ("ADDRESS"). ToString
  
  
Me. TextBox3.Text=Dv(0) ("TARGET"). ToString
  
  
Me. TextBox4.Text=Dv(0) ("ICON"). ToString
  
  
End Sub
  
  
Private Function FromIdToNode (ByVal ID As String,
ByVal Nds As TreeNodeCollection) As TreeNode
  
  
'Search nodes with keywords
  
  
Dim I As Integer
  
  
Dim tmpNd As TreeNode, tmpNd1 As TreeNode
  
  
For Each tmpNd In Nds
  
  
IfTmpNd. ID= ID Then
  
  
Return tmpNd
  
  
Exit Function
  
  
End If
  
  
TmpNd1=FromIdToNode(ID, tmpNd. Nodes)
  
  
If Not (tmpNd1 Is Nothing) Then
  
  
Return tmpNd1
  
  
Exit Function
  
  
End If
  
  
Next
  
  
Return Nothing
  
  
End Function
 
 

Iv. Conclusion

The preceding sections describe how to modify database data while adding, deleting, modifying, and moving Tree nodes. Due to space limitations, the author only introduces the basic ideas, processes and key steps here, and does not list the detailed source code. Readers can complete it on their own. If you need detailed source code, you can contact me. In this article, the program has been debugged under VS. NET, SQLServer, Windows 2000, and IIS5.0.

1. DataList and Repeater controls of ASP. NET
2. Analysis of IIS ing in ASP. NET
3. Overview ASP. NET status types
4. Introduction to ASP. NET and Web servers
5. EnableViewState attribute of ASP. NET