vb.net - .NET Tab Control Selected Index - strange behaviour -

i have tab control 7 pages in it. have view model enables 2 buttons backwards , forwards navigation through tab control. working fine, has started behaving strangely, when positioned on tab index 1, , want set tab index 0, selects tab index 3, , displays tab page no controls on it. pressing button other tab page has no problems , pressing forward button, similar. tried 'hard-coding' selected tab, , got same results. code shown below:

public class viewmodel      private withevents tabcontrol tabcontrol  . . .     public sub nexttab()         if tabcontrol.selectedindex < tabcontrol.tabcount             tabcontrol.selectedindex += 1         end if     end sub      public sub previoustab()         if tabcontrol.selectedindex > 0             ' code in if statement below trying work around problem, none of has been successful             if tabcontrol.selectedindex = 1                 'tabcontrol.selectedindex = 0                 tabcontrol.selectedtab = tabcontrol.tabpages(0)                 tabcontrol.tabpages(0).focus()             else                 tabcontrol.selectedindex -= 1             end if         end if     end sub . . . end class  dim vm new viewmodel(tcinfotabs) . . .   private sub btnnext_click(sender object, e system.eventargs) handles btnnext.click     vm.nexttab() end sub  private sub btnprevious_click(sender object, e system.eventargs) handles btnprevious.click     vm.previoustab() end sub 

trying move tab index 1 index 0 results in moving index 3. hard coding position in immediate window has same result: tabcontrol.selectedindex = 1 -> ends pointing 3. there no other events in rest of form. if on tab 2 , subtract 1 end on tab 1. if on tab 1 , subtract 1 end on tab 3. working, , stopped. using .net 4.0, suggestions welcome.

found answer: pebkac - problem exists between keyboard , chair. @ bottom of each tab page, had small textbox user tabbed through fields on tab page, automatically move user next tab when entered. field @ bottom of tab order each of tab pages. however, when first tab page selected, enter event field fired, moving next page, same event fire, , same again on next page. happened when moving backwards. no idea why enter event fire field @ end of tab order , if changed tab index under program control. clicking on first tab did not fire enter event field.

short fix - kludge - add flag set buttons each time user moved forward or backward telling field event not fire.