Dynamic Treeview Height

dynamic, height, treeview, vb.net, winforms

Solution

Handle AfterExpand / AfterCollapse Events

Add the event handlers AfterExpand and AfterCollapse to make the treeview react to the expanding / collapsing of the nodes. I hardcoded the padding for this example, but essentially this is just the height of the menus, buttons, etc that will be used to resize the form.

Private Sub Rapports_tvAllReports_AfterExpand(sender As Object, e As System.Windows.Forms.TreeViewEventArgs) Handles Rapports_tvAllReports.AfterExpand, Rapports_tvAllReports.AfterCollapse
    Dim Padding As Integer = 140 'Customize this, basically accounts for all buttons or menus included in the form which nests the treeview
    Dim TreeViewHeight As Integer = GetOpenedNodesRecursively(Rapports_tvAllReports)

    If formWindow = FormWindowState.Normal Then Me.Size = New Size(345, TreeViewHeight + Padding)
End Sub

All we do is increment the Y and set that new Y to the form. In order for the treeview to correctly resize along with the form, anchor it to the top and bottom.

Recursively go through nodes

This function will go through the root nodes and call a recursive function on the opened nodes.

Private Function GetOpenedNodesRecursively(ByVal aTreeView As TreeView)
    Dim Y As Integer = 0

    'Go through each node of the treeview (first level)
    For Each n As TreeNode In aTreeView.Nodes
        Y += Rapports_tvAllReports.ItemHeight

        'If the user expands a node, recursively increment the Y
        If n.IsExpanded Then Y += RecursiveYIncrement(n)
    Next

    Return Y
End Function

Now just keep incrementing the TreeViewHeight using the recursive function that will return the height (Y) of all nodes that are expanded in the current tree view.

Private Function RecursiveYIncrement(ByVal n As TreeNode)
    Dim Y As Integer = 0

    'Go through each node of the treeview (first level)
    For Each aNode As TreeNode In n.Nodes
        Y += Rapports_tvAllReports.ItemHeight

        'If the user expands a node, recursively increment the Y
        If aNode.IsExpanded Then Y += RecursiveYIncrement(aNode)
    Next

    Return Y
End Function

Visual Reproduction

Here is how it looks when we're done:

We start with a collapsed tree view

We can then expand some nodes and the form will grow accordingly

And then we can re-collapse the nodes and expand more, the form adjusts again!

Forgive me for the French in the screenshots, it's the norm here in Quebec... We're obligated to do so!

Problem

Original source