vb.net - Simple Quiz in VB -

i taking vb general education class totally non related major. struggling here 1 of our assignments. assignment create simple quiz consisting of 3 questions, , program supposed calculate score , percentage of participant. have written following code far, doesn't execute right. can me please? thing can't figure out how make 1 of textboxs' case insensitive. great!

private sub btnsubmit_click(sender object, e eventargs) handles btnsubmit.click     dim firstanswer integer = 2     dim secondanswer string = "barak obama"     dim thirdanswer string = "florida"     dim correctanswer double = 0     dim num1 double = cdbl(lblcorrectanswer.text)     dim percent double     percent = num1 / 3 * 100      if txtsum.text = firstanswer , txtpresident.text = secondanswer , txtimpoertantques.text = thirdanswer         lblcorrectanswer.text = correctanswer + 3         txtsum.backcolor = color.green         txtsum.forecolor = color.white         txtpresident.backcolor = color.green         txtpresident.forecolor = color.white         txtimpoertantques.backcolor = color.green         txtimpoertantques.forecolor = color.white         lblprecent.text = percent.tostring("##.00") & "%"     elseif txtsum.text = firstanswer , txtimpoertantques.text = thirdanswer         lblcorrectanswer.text = correctanswer + 2         txtsum.backcolor = color.green         txtsum.forecolor = color.white         txtimpoertantques.backcolor = color.green         txtimpoertantques.forecolor = color.white         txtpresident.backcolor = color.red         txtpresident.forecolor = color.white         lblprecent.text = percent.tostring("##.00") & "%"     elseif txtsum.text = firstanswer         lblcorrectanswer.text = correctanswer + 1         txtsum.backcolor = color.green         txtsum.forecolor = color.white         txtpresident.backcolor = color.red         txtpresident.forecolor = color.white         txtimpoertantques.backcolor = color.red         txtimpoertantques.forecolor = color.white         lblprecent.text = percent.tostring("##.00") & "%"     elseif txtsum.text = firstanswer , txtpresident.text = secondanswer         lblcorrectanswer.text = correctanswer + 2         txtsum.backcolor = color.green         txtsum.forecolor = color.white         txtpresident.backcolor = color.green         txtpresident.forecolor = color.white         txtimpoertantques.backcolor = color.red         txtimpoertantques.forecolor = color.white         lblprecent.text = percent.tostring("##.00") & "%"     elseif txtpresident.text = secondanswer , txtimpoertantques.text = thirdanswer         lblcorrectanswer.text = correctanswer + 2         txtpresident.backcolor = color.green         txtpresident.forecolor = color.white         txtimpoertantques.backcolor = color.green         txtimpoertantques.forecolor = color.white         txtsum.backcolor = color.red         txtsum.forecolor = color.white         lblprecent.text = percent.tostring("##.00") & "%"     elseif txtpresident.text = secondanswer         lblcorrectanswer.text = correctanswer + 1         txtpresident.backcolor = color.green         txtpresident.forecolor = color.white         txtsum.backcolor = color.red         txtsum.forecolor = color.white         txtimpoertantques.backcolor = color.red         txtimpoertantques.forecolor = color.white         lblprecent.text = percent.tostring("##.00") & "%"     elseif txtimpoertantques.text = thirdanswer         lblcorrectanswer.text = correctanswer + 1         txtimpoertantques.backcolor = color.green         txtimpoertantques.forecolor = color.white         txtsum.backcolor = color.red         txtsum.forecolor = color.white         txtpresident.backcolor = color.red         txtpresident.forecolor = color.white         lblprecent.text = percent.tostring("##.00") & "%"     else         lblcorrectanswer.text = correctanswer = 0         lblprecent .text = 0         txtsum.backcolor = color.red         txtsum.forecolor = color.white         txtpresident.backcolor = color.red         txtpresident.forecolor = color.white         txtimpoertantques.backcolor = color.red         txtimpoertantques.forecolor = color.white     end if      if txtsum.text = nothing or txtpresident.text = nothing or txtpresident.text = nothing         messagebox.show("error! please enter aswer.")     end if 

there 3 questions there must 3 if...elseif...else or if..else. should not include scoring of other questions inside elseif because once program returns true in either of if or elseif in conditions if..else terminates , not execute rest of elseif..

it should example,

if txtsum.text=.... elseif else end if  if txtpresident.text=... else end if  if txtimpoertantques.text=... else end if 

rest assured, execute wanted... or this...

private sub btnsubmit_click(byval sender system.object, byval e system.eventargs) handles btnsubmit.click     dim firstanswer integer = 2     dim secondanswer string = "barak obama"     dim thirdanswer string = "florida"     dim correctanswer double = 0     dim num1 double = cdbl(lblcorrectanswer.text)     dim percent double     percent = num1 / 3 * 100     if txtsum.text = nothing or txtpresident.text = nothing or txtpresident.text = nothing         messagebox.show("error! please enter aswer.")         'when empty rest won't executed         'instead, program prompts user enter answer     else         if txtsum.text = firstanswer             correctanswer = correctanswer + 1 'added points             txtsum.backcolor = color.green             txtsum.forecolor = color.white             lblprecent.text = percent.tostring("##.00") & "%"         end if          if txtsum.text = firstanswer             correctanswer = correctanswer + 1 'added points             txtsum.backcolor = color.green             txtsum.forecolor = color.white             lblprecent.text = percent.tostring("##.00") & "%"         end if          if txtimpoertantques.text = thirdanswer             correctanswer = correctanswer + 1 'added points             txtimpoertantques.backcolor = color.green             txtimpoertantques.forecolor = color.white             lblprecent.text = percent.tostring("##.00") & "%"         end if          lblcorrectanswer.text = correctanswer 'displays total score      end if 'end of empty field validation end sub