tony said:
Hello,
The default value works for adding row. If you are in edit mode the value that is in the grid is selected in the edit form. If the value can not be found (i.e. there are differences in the grid data and the definitions in editoptions) the first value is used. In order to do what you want in edit mode you maybe will need to use beforeShowForm event.
Regards
Tony
maybe i can save someone for tearing his hairs out……. 
in my case….(in form editing: select value forgot his grid-value and showed first-select value…)