Hi Marcel,
Thank you for using Syncfusion Products.
We have checked your query “ChildNodes are not loaded when used LoadOnDemandCommand and ChildPropertyName” from our side. When you set both LoadOnDemandCommand and ChildPropertyName for same SfTreeView, ChildNodes for particular item you needed to load initially while loaded will be loaded. You have to return false in the CanExecute method of LoadOnDemandCommand, for the node to which you have to load ChildNodes initially when loaded.
To display some ChildNodes when opening the page, you need to set AutoExpandMode property to either AllNodesExpanded or RootNodesExpanded.
You can download the sample from following location.
Please let us know, if you have any query.
Regards,
Subburaj Pandian V