Implementation of tree functions in ASP. NET (1)

Tree charts are used to display data organized by tree structures. They are widely used, such as file systems (resource managers in Windows) in computers and composition structures 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 a tree chart. Due to the complex structure of the tree chart, 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.

Internet Explorer webcontrols is not in vs. Net's Standard Server Control, to download to Microsoft's site, is: http://msdn.microsoft.com/downloads/samples/internet/default.asp? Url =/downloads/samples/Internet/asp_dot_net_servercontrols/webcontrols/default. asp when you download and install it for the first time, right-click the Toolbox customize toolbox... → In. NET Framework components, select Micosoft. Web. UI. webcontrols. Treeview, And the Treeview control appears in the toolbox.

　　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. Count-1). nodes, intid) Next End sub