Customer support > Feature Requests

Virtual Mode like System.Windows.Forms.ListView

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Filippo: [Edit]
Hi,

  I need the behaviour of VirtualMode property of  System.Windows.Forms.ListView control.
  I need to set a "VirtualTreeSize" and an event like RetrieveVirtualItem to build data on demand.

  Is it possible right now or it's a new feature to implement?

  Thank you,
    Filippo.

Ruslan:
Hello and welcome to the forums.

This features already implemented as load on demand, which you can enable for every separate node by using the node.LoadOnDemand property.
To load children nodes manually please enable the specified property for all root nodes and subscribe to the treeview.NodeExpanding event where load children nodes for such node:
Code: [Select]>>>>someNode.LoadOnDemand = true;

private void tree_NodeExpanding(FlexibleTreeView pTreeview, NodeExpandingEventArgs pArgs)
{
  if (pArgs.Node.LoadOnDemand)
  {
    pArgs.Node.LoadOnDemand = false;
 
    // load node`s children here...
  }
}
<<<<
You can enable this mode for the bound nodes (when treeview is bound to a data source) as well.

Feel free to contact us if you have other questions.

Filippo: [Edit]
Thank you for your reply,
  is it possible to demand loading not only subitems but also nodes attached to the root?
  I need to set a virtual length, for example 1.000.000 items (flat structure), see the scrollbar resize accordantly.
  When I scroll I'd like to load only needed data, only 10-20 visible items. Like pagination when you access to a huge database table.

  Thank you,
    Filippo.

Ruslan:
Unfortunately, Flexible TreeView doesn`t support such functionality. On the other hand, in the forthcoming release which will be available soon we`ve greatly optimized the control performance so it easily manage 1 000 000 items (now it takes only 4.8 seconds to attach such huge data source to the treeview). So if your table is available to read all items at once this may be the way to go. Of course this way consumes more memory comparing with a virtual tree.

Filippo: [Edit]
Ok, I have supposed that.

Just last question: do you think that it's impossible to develop (architectural speaking) or it's only due to lack of time? Or for you this is not an interesting develop task to do?

Thank you for you time,
  Filippo.

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