'Declaration Public Property ChildNodes As NodeCollection
public NodeCollection ChildNodes {get; set;}
Default value of the property is null and therefore you need to set the property to a new NodeCollection in order to specify the child nodes. Also the same instance of NodeCollection cannot be set on multiple Node objects.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2