Infralution Support

[jkempner]

The standard behavior in a Windows Forms tree control is to remember which sub-nodes were expanded when a node is collapsed and then re-expanded. The default behavior in VirtualTree (I'm using 3.15) appears to be that all children, grandchildren, etc. get collapsed when their parent is collapsed. Is there a way to get around this, so that when I collapse and then re-expand a row, the children of that row that were expanded before their parent was collpased are still expanded?

For what it's worth, I'm using programmatic data binding in the control where I see this behavior.

[Infralution]

Virtual tree will also remember the expanded sub nodes and rexpand them. You can see this behaviour by running the Simple Tree sample.

I think the problem is that your GetChildren method is probably returning a new set of objects each time it is called. Virtual Tree saves references to the data objects that have been been expanded by the user and then will look for rows corresponding to these items to try and re-expand them. If you have actually created new objects then these won't match and the object won't be expanded.

Normally you want to implement some form of caching of your data objects so that you aren't creating new data objects if there already was an existing object. This also avoids possible problems with aliasing - where Virtual Tree holds a reference to one version of an object and your application has a reference to another object - which represents the same data.
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Infralution Support