How to set submit button in vb.net -

when want calculate result, have entered in textbox.

i connected them local database.

but use these codes terminate score entry if students list ended.

dim assessmentrecords = select p                         p in db.assessments                         p.class = cboclass.text     if recordposition + 1 < assessmentrecords.count        msgbox("end of records reached!", msgboxstyle.exclamation + msgboxstyle.okonly)        exit sub     end if 

when debugged software, can't enter score keeps telling me "end of records reached"

i don't know how deals problem , sometime can put 1 person , terminates , use lineq sql in connection local database.

i appreciate help, thank you!