Binaryworld - Load items faster in the TreeView and ListView controls ... [ VB -> Windows Common Controls ]

There is an easy, but under-utilized, technique for loading many nodes in a TreeView control (or ListItems in a ListView control) that is faster than the standard technique. Consider this loop:

Click here to copy the following block

For i = 1 To 5000
TreeView1.Nodes.Add , , , "Node " & i
Next

Instead of repeatedly query the TreeView1 object for its Nodes collection, you can store it in a temporary object variable:

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Dim nods As MSComctlLib.Nodes
Set nods = TreeView1.Nodes

For i = 1 To 5000
nods.Add , , , "Node " & i
Next

You don't even need the temporary variable, if you use a With block:

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With TreeView1.Nodes
  For i = 1 To 5000
    .Add , , , "Node " & i
  Next
End With

On my system, these optimized loops run about 40% faster than the standard code showed above. This faster speed can be explained as follows: by storing the Nodes collection in a temporary variable (or using the hidden temporary variable that VB builds behind the With block), you avoid to bind the Nodes object to its parent TreeView1 object inside the loop. Because this latter binding is based on the inefficient dispid-binding, this step trims a lot of unnecessary overhead inside the loop.
The same reasoning applies to other ActiveX controls:

the ListItems, ListSubItems, and ColumnHeaders collections of the ListView control
the Buttons and ButtonMenus collection of the Toolbar control
the ListImages collection of the ImageList control
the Panels collection of the StatusBar control
the Tabs collection of the TabStrip control
the ComboItems collection of the ImageCombo control the Columns collection of the DataGrid control and more in general, whenever you have an ActiveX control that exposes a collection that you use inside a loop.