<grid>
<grid.columndefinitions>
<columndefinition width="475" />
<columndefinition width="*" />
</grid.columndefinitions>
<grid.rowdefinitions>
<rowdefinition height="*" />
<rowdefinition height="200" />
</grid.rowdefinitions>
//CODE stuff here
// like <dockpanel grid.column="0" grid.row="0" mode="hold" /></grid>
Now, when I expand the treeview, the border grows with it. I'd still like to find a way to maximize the border on full screen, but this will work.