In this article we will learn that how to create TreeView control from datatable object in vb.net language.
This example requires one windows form with TreeView control named TreeView1.
First we create a datatable object and then we will bind treeview with node like this:
Public Function CreateDataTable() As DataTable Dim dataTable As New DataTable() dataTable.Columns.Add("Country") ' The value in this column will display on the TreeNode dataTable.Columns.Add("City") ' The value in this column will identify its parentId ' Fill the DataTable dataTable.Rows.Add("India", "New Delhi") dataTable.Rows.Add("India", "Mumbai") dataTable.Rows.Add("India", "Kolkata") dataTable.Rows.Add("India", "Noida") dataTable.Rows.Add("USA", "New York") dataTable.Rows.Add("USA", "Washington") dataTable.Rows.Add("USA", "") dataTable.Rows.Add("USA", "India") Return dataTable End Function
above datatable has data like this
And now we will create TreeView from above datatable. This example also learn that how to create TreeView at runtime or how to bind TreeView nodes to TreeView control at runtime.
Public Sub BuildTree(ByVal dt As DataTable, ByVal trv As TreeView, ByVal expandAll As [Boolean]) ' Clear the TreeView if there are another datas in this TreeView trv.Nodes.Clear() Dim node As TreeNode Dim subNode As TreeNode For Each row As DataRow In dt.Rows 'search in the treeview if any country is already present node = Searchnode(row.Item(0).ToString(), trv) If node IsNot Nothing Then 'Country is already present subNode = New TreeNode(row.Item(1).ToString()) 'Add cities to country node.Nodes.Add(subNode) Else node = New TreeNode(row.Item(0).ToString()) subNode = New TreeNode(row.Item(1).ToString()) 'Add cities to country node.Nodes.Add(subNode) trv.Nodes.Add(node) End If Next If expandAll Then ' Expand the TreeView trv.ExpandAll() End If End Sub
Private Function Searchnode(ByVal nodetext As String, ByVal trv As TreeView) As TreeNode For Each node As TreeNode In trv.Nodes If node.Text = nodetext Then Return node End If Next End Function
Excellent! Thank you! This has explained and helped me understand the syntax much better than the microsoft example, which requires you use a dataarray for storing the indexes of Parent Nodes. I was thinking though, wouldn’t a Dictionary be quicker and more efficient for that rather than iterating through every node with the search function each time?
Yes you can use Dictionary to search.
Very useful. Perhaps you might consider talking about the opposite task as well: saving a TreeView into a datatable.
Thank you Tim,
I have added your suggestion in my todo list. I will notify you when it will be available.
FYI, your ‘Searchnode’ function doesn’t return a value on all of its code paths.
Hi, I want to know if it could work for more layers of the tree, not only two layers
hey I have most the code working, the private searchnode function isn’t working though. I have tried to change it to where it is not a function and can be ran from form1. Here is what I tried:
For Each nodes As TreeNode In TreeView1.Nodes(0).Nodes
If nodes.Text = nodes.Text Then
nodes.Remove()
End If
Next
but it does not remove the same named node, what am I doing wrong?