Ehm, treeViewBonk is just my example, in your code it is probably still called treeView1

But it should go under as a child of textbox1.text
That is what I tried to demonstrate in my previous post. Read it again.

Code:
TreeNode tr3 = new TreeNode();
tr3 = treeView1.SelectedNode;
You are still doing that part wrong. You create a new TreeNode, but discard it right away by passing the selected node to the tr3 variable.
Just type it like:
Code:
TreeNode tr3 = treeView1.SelectedNode