How to cancel the vertical scroll automaticlly changed

Question

Hi

I have ListBox with Expander as a ListBoxItem, and i have some checkbox and ComboBox within Expander,

I placed the ListBox within the ScrollBar.

problem: For example ListBox have 10 ExpanderItem,

When i expand any one of the Expander then Vertical Scroll viewer will display.

now i scroll the Vertical ScrollBar to below for see all controls placed in the Expander,

when i click checkBox or press the ComboBox with in Expander, then vartical ScrollBar automatically move to some position above.

How to cancel the vertical scroll automaticlly changed when i click with in the Expander.