Why control jump to combobox_selectindexchanged event ?

 

I have an array of 30 Combobox in windows form application.I populate these combobox from database on combobox1_selectindexchanged event.

when it has text="08.SL  " or "09.EL  " or "07.CL  " it move to combobox_selectindexchanged event.

Why it jump to  combobox_selectindexchanged event.