wpf how to prevent treeview exceeding window size

My reference is, 

To set the MaxHeight attribute of the treeview control in relation to the size of the window it was hosted in When the MaxHeight is surpassed, we also require the scrollbar to appear.

I added the event to the XAML window tag.

SizeChanged="Window SizeChanged"

Then, in the code-behind, I implemented an event to set the treeview's MaxHeight relative to the window's ActualHeight. I utilised an 85 percent ratio. The tree view will be 85 percent of the window's height.

Window SizeChanged is a private void (object sender, SizeChangedEventArgs e)

treeView1.MaxHeight = actualHieght *.85; double actualHieght = NameOfTheWindow.ActualHeight;

All of the prerequisites have been met. When the contents of the treeview surpass the MaxHeight, the treeview grows in size relative to the window, and the vertical scrollbar appears.