How to select all the child nodes without selecting the parent node of a treeview in 1803 version

Question

I am using a treeview control in my uwp project which supports 1803 version. I will add the nodes to selected nodes programmatically when it is clicked. Consider a parent node with a single child node. When the child node is clicked, I will add it to the selected nodes programmatically but the parent node also added to selected nodes automatically. I don't want the parent node to be added to the selected nodes. Is there any way we can restrict it? It would be much helpful if the solution is provided in C#. Thanks in advance.