Easy way to properly save and load a treeview-structure

Shows the - in my opinion - easiest way how to properly save and load a complete treeview structure from a plain text-file. NOTE : The code uses 2 functions - GetBefore and GetAfter - which I got from this Site, but I cannot remember the name of the author. If the person who wrote these functions incidentally gets this code, please leave your name in the comments, mentioning that these are YOUR, NOT MINE.