Imports System
Imports EnvDTE
Imports EnvDTE80
Imports System.Diagnostics

Public Module CollapseAll
    Sub CollapseNode(ByRef item As UIHierarchyItem)

        Dim subitem As UIHierarchyItem
        For Each subitem In item.UIHierarchyItems
            If (subitem.UIHierarchyItems.Expanded = True) Then
                CollapseNode(subitem)
                subitem.UIHierarchyItems.Expanded = False
            End If
        Next

    End Sub

    Sub CollapseAll()

        ' Get the the Solution Explorer tree
        Dim UIHSolutionExplorer As UIHierarchy
        UIHSolutionExplorer = DTE.Windows.Item(Constants.vsext_wk_SProjectWindow).Object()

        ' Check if there is any open solution
        If (UIHSolutionExplorer.UIHierarchyItems.Count = 0) Then
            ' MsgBox("Nothing to collapse. You must have an open solution.")
            Return
        End If

        ' Get the top node (the name of the solution)
        Dim UIHSolutionRootNode As UIHierarchyItem
        UIHSolutionRootNode = UIHSolutionExplorer.UIHierarchyItems.Item(1)

        CollapseNode(UIHSolutionRootNode)

        ' Select the solution node, or else when you click on the solution window
        ' scrollbar, it will synchronize the open document with the tree and pop
        ' out the corresponding node which is probably not what you want.
        UIHSolutionRootNode.Select(vsUISelectionType.vsUISelectionTypeSelect)

    End Sub
End Module