In a treeview with checkbox, when the number of elements is superior to 10, if we check an element with an id superior to 10 (or 10), the element with the id : 1 switch to the indeterminate state.

This very simple function will handle all Checkboxes (parents & childs) of a TreeView control. If you click a child node it will check all parents of this node. Also, if you "uncheck" a child node ...