Using Else IF in Eval for ASP.NET

I have a code from .asp and want to convert it to .aspx, how to convert it in proper way for the code. the code are shown below. thank you.

if isnull(RSTrx("notVerifyRsn")) and not isnull(RSTrx("notVerifyRsn")) then
                                reason = trim(RSTrx("notAppRsn"))
                            elseif not isnull(RSTrx("notVerifyRsn")) and isnull(RSTrx("notVerifyRsn")) then
                                reason = trim(RSTrx("notVerifyRsn"))
                            end if