Efficient TreeView construction method
I have always had a friend on the Internet that TreeView on the .Net is not fast enough, and it is not convenient. So what is the real situation? I need a quick Tree in a project, its data source is MS SQL, and the structure recorded in the corresponding table is as follows:
ID FatherID Title 0101 01 Basic Construction Expenditure 010109 0101 Other Basic Construction Expenditures
It is characterized by a string that the ID of the parent node is exactly the length of the current record ID.
So I wrote the following code:
First, ordinary approach
Private function buildentree (Byval DS AS Dataset)
DIM RS AS DATAROWCOLLECTION
DIM R AS DATAROW
DIM ID As String
Dim Fatherid As String
DIM TITLE As String
DIM FN As Treenode
Dim Node as Treenode
RS = ds.tables (0) .ROWS
Bootnode = New Treenode
Bootnode.text = "[0] All Units"
BootNode.tag = "0" 'root directory
Treeen.Nodes.Add (bootnode)
For Each R in Rs
ID = Directcast (R.Item (0), String) .trim 'CODE
Fatherid = Directcast (R.Item (1), String) .trim 'Fathercode
Title = "[" & id & "]" & Directcast (r.Item (2), string) .trim 'Title
'Find the same node as the parent point ID
Fn = findNode (Father)
IF fn is nothing then
'Nodes that did not find the corresponding ID
Else
Node = new TREENODE
With node
.Tag = ID
.Text = Title
End with
Fn.nodes.add (node)
END IF
NEXT
Bootnode.expand ()
END FUNCTION
'Look for the ID match node under the specified node
Private function FindNode (byval n as treeode, byval id as string) as Treenode
DIM NS as TreenodeCollection
Dim Node as Treenode
Dim flag as boolean
DIM STRText As String
Dim returnnode as treenode
Flag = false
IF n.tag = id life
Return N
Else
'If the path is not the same, return
IF (id.Length
Return Nothing
END IF
ns = n.nodes
For Each Node in NS
ReturnNode = FindNode (Node, ID)
If returnnode is nothing then
'do nothing
Else
Flag = TRUE
EXIT Forend IF
NEXT
IF flag = true kiln ing retrnode
END IF
Return Nothing
END FUNCTION
The above code uses the ID value of the current word node to the Node's TAG, and then starts traversal from the root directory. It is found that its efficiency is extremely low after operation. But there are mostly the case online.
Is there any other way to increase its running speed.
God said: "Algorithm either in space change time, either in time."
I was ambiguing at some point. I found that I can provide Hashtable provided by. Net, this is a good stuff.
So how do you use it?
Second, fast way
First we need to add a definition
Private fasthashtable as hashtable
Then you need to make a small adjustment of BuildEntree.
Private function buildentree (Byval DS AS Dataset)
DIM RS AS DATAROWCOLLECTION
DIM R AS DATAROW
DIM ID As String
Dim Fatherid As String
DIM TITLE As String
DIM FN As Treenode
Dim Node as Treenode
RS = ds.tables (0) .ROWS
Bootnode = New Treenode
Bootnode.text = "[0] All Units"
BootNode.tag = "0" 'root directory
Treeen.Nodes.Add (bootnode)
Fasthashtable.Add ("0", bootnode)
For Each R in Rs
ID = Directcast (R.Item (0), String) .trim 'CODE
Fatherid = Directcast (R.Item (1), String) .trim 'Fathercode
Title = "[" & id & "]" & Directcast (r.Item (2), string) .trim 'Title
'Find the same node as the parent point ID
Fn = findNode (Father)
IF fn is nothing then
'Nodes that did not find the corresponding ID
Else
Node = new TREENODE
With node
.Tag = ID
.Text = Title
End with
Fn.nodes.add (node)
FasthashTable.Add (ID, Node)
END IF
NEXT
Bootnode.expand ()
END FUNCTION
As seen from the above code, I just increased the code of the two black body. Its role is to store the new node not only to TreeView, but also save to FashHashTable, whose keyword is ID value, as long as there is no repetition ID Then you can use it.
Next we also need to change FindNode.
'New version fast look
Private function findnode (byval id as string) as Treenode
Return fasthashtable.Item (ID)
END FUNCTION
Ok, now there is a job to do, just to make the foundhashtable to initiate it, try to make the initiator to the same number of data nodes you will build, I am 3000 nodes in this system, so I added the following One sentence:
Fasthashtable = New hashtable (3000) 'The number is now very fast.
Third, post
Even in the .NET era, the data structure is also very useful to us. I am here today!
