Iterate and remove duplicate tree nodes from database into treeview

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So, I was able to combine 2 methods to come up with a way to remove duplicate tree nodes. Right now my problem is I can only do 1 iteration per function I have. I want to be able to use the same function and pick multiple cells to fill the treeview. What I have noew works great if all you want it 1 column generate the treeview with no duplicates. Here is what I have now:

Private Function Searchnode(ByVal nodetext As String, ByVal treeview1 As TreeView) As TreeNode

       Dim newNode As TreeNode = New TreeNode(nodetext)

       For Each node As TreeNode In treeview1.Nodes(0).Nodes
           If node.Text = nodetext Then
               node.Remove()

           End If
       Next

       treeview1.Nodes(0).Nodes.Add(newNode)
       Return newNode


   End Function


   Public Sub Remove_treeview_duplicates()
       TreeView1.Nodes.Add("treenode")

       Dim node As TreeNode

       For Each row As DataRow In Database1DataSet.Table.Rows
           'search in the treeview if node is already present
           node = Searchnode(row.Item(3).ToString(), TreeView1)

       Next

   End Sub

I want to generate the treeview with no duplicate information with certain Row.items, instead of just the 1.

What I have tried:

I made other functions to do the same effects, but there has to be a way for 1 function to control the lot.

Posted 9-Jan-17 6:57am

Member 11856456

Updated 9-Jan-17 8:43am

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Wendelius · Accepted Answer · 2017-01-09T08:03:00

Not sure if I understand the question correctly but from what I gather you want to remove matching nodes regardless on what level they are found. In order to do that you need a recursion.

Have a look at the following example. First I add some nodes to the tree view and then remove all elements containing text B

VB

    Dim treenode As TreeNode

    ' Add example data
    treenode = Me.TreeView1.Nodes.Add("A")
    treenode.Nodes.Add("B")
    treenode.Nodes.Add("C")

    treenode = Me.TreeView1.Nodes.Add("B")
    treenode = treenode.Nodes.Add("C")
    treenode.Nodes.Add("D")

    treenode = Me.TreeView1.Nodes.Add("C")
    treenode = treenode.Nodes.Add("B")
    treenode.Nodes.Add("A")

    'recursively remove desired nodes
    Me.RemoveNodesByText("B", Me.TreeView1)


End Sub

Private Function RemoveNodesByText(ByVal nodetext As String, ByVal treeview1 As TreeView, Optional childnode As TreeNode = Nothing) As Boolean
    Dim nodesToIterate As TreeNodeCollection

    If childnode Is Nothing Then
        nodesToIterate = treeview1.Nodes
    Else
        nodesToIterate = childnode.Nodes
    End If

    For nodecounter As Integer = nodesToIterate.Count - 1 To 0 Step -1
        ' recursively loop through children
        RemoveNodesByText(nodetext, treeview1, nodesToIterate(nodecounter))
        ' remove this node if matches the given node text
        If nodesToIterate(nodecounter).Text = nodetext Then
            nodesToIterate(nodecounter).Remove()
        End If
    Next

    Return True
End Function

One thing is that in the example code the new node isn't added inside the recursive function. Otherwise multiple new nodes would be created so if you want to ensure that only one node of a kind exists, first remove duplicates and after that add the new node to desired location.