Question

If TreeView.SelectedNode = null is used, would it also null the node object on the SelectedNode?

Answer 1

You appear to be confusing references and objects. You can have a null-reference (which refers to no object at all), but there is no such thing as a null-object in C#.

If on the other hand, you are concerned that setting the SelectedNode property to null will evict the currently selected node from the TreeView, this is not the case – that node will simply be unselected.

EDIT: Perhaps you are concerned that the values of other variables that hold references to the currently-selected node will be set to null should the SelectedNode property be set to null. This is not the case either:

TreeView treeView = ...

TreeNode node = new TreeNode();    
treeView.Nodes.Add(node);

treeView.SelectedNode = node;

treeView.SelectedNode = null; 
bool isNodeNull = (node == null); // false