vb.net - Is this the correct approach to customizing the ASP.Net MVC 4 template Login -

while mvc4 template provided microsoft useful, feel there few scenarios should covered out users trying log in.

1. allow user log in email address instead of user name (they can still choose use user name). former easier remember.
2. if don't have local account , try use one, check if have used external provider (such google) log in , let them know use instead.
3. if have registered account locally have not yet confirmed email, let them know. current template warns username or password wrong.

maybe i'm over-thinking it, want provide user every opportunity log in , use site. here code wrote add these functions. wrote in vb, including c# tag since majority of mvc user's here seem favor , vb easy read. correct approach add these options? there glaring errors code, aside fact can refactor it? thank you.

<httppost()> _ <allowanonymous()> _ <validateantiforgerytoken()> _ public function login(byval model loginmodel, byval returnurl string) actionresult     if modelstate.isvalid         if isemail(model.username)             'the username email address             dim username = getusernamebyemail(model.username)             if username isnot nothing                 if websecurity.login(username, model.password, persistcookie:=model.rememberme)                     return redirecttolocal(returnurl)                 end if                 'check if there local account                 dim localid = getuseridbyemail(model.username)                 if localid nothing                     'no local account means username wrong                     modelstate.addmodelerror("", "the user name or password provided incorrect.")                 else                     if not oauthwebsecurity.haslocalaccount(localid)                         'registered via external provider                         modelstate.addmodelerror("", "please login external provider have used.")                     else                         if not websecurity.isconfirmed(model.username)                             'has local account, hasn't confirmed email                             modelstate.addmodelerror("", "you have not yet confirmed email.")                         else                             'password wrong                             modelstate.addmodelerror("", "the user name or password provided incorrect.")                         end if                     end if                 end if             else                 modelstate.addmodelerror("", "the email entered incorrect.")             end if         else             'must regular user name, log in normal             if websecurity.login(model.username, model.password, persistcookie:=model.rememberme)                 return redirecttolocal(returnurl)             end if             'check if there local account             dim localid = getuseridbyusername(model.username)             if localid nothing                 'no local account means username wrong                 modelstate.addmodelerror("", "the user name or password provided incorrect.")             else                 if not oauthwebsecurity.haslocalaccount(localid)                     'registered via external provider                     modelstate.addmodelerror("", "please login external provider have used.")                 else                     if not websecurity.isconfirmed(model.username)                         'has local account, hasn't confirmed email                         modelstate.addmodelerror("", "you have not yet confirmed email.")                     else                         'password wrong                         modelstate.addmodelerror("", "the user name or password provided incorrect.")                     end if                 end if             end if         end if     end if     return view(model) end function  'check if input email address public function isemail(byval input string) boolean     return regex.ismatch(input, "\a(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?)\z") end function  public function getusernamebyemail(byval email string) string     dim username string = nothing     dim conn sqlconnection = new sqlconnection(system.configuration.configurationmanager.connectionstrings("defaultconnection").connectionstring)     dim cmd sqlcommand = new sqlcommand("select username user_info email = @email", conn)     cmd.parameters.add(new sqlparameter("@email", system.data.sqldbtype.nvarchar))     cmd.parameters("@email").value = email     conn.open()     dim reader sqldatareader = cmd.executereader()     try         while reader.read             username = reader(0)         end while             reader.close()     end try     conn.close()     return username end function  public function getuseridbyemail(byval email string) integer?     dim userid integer?     dim conn sqlconnection = new sqlconnection(system.configuration.configurationmanager.connectionstrings("defaultconnection").connectionstring)     dim cmd sqlcommand = new sqlcommand("select userid user_info email = @email", conn)     cmd.parameters.add(new sqlparameter("@email", system.data.sqldbtype.nvarchar))     cmd.parameters("@email").value = email     conn.open()     dim reader sqldatareader = cmd.executereader()     try         while reader.read             userid = reader(0)         end while             reader.close()     end try     conn.close()     return userid end function  public function getuseridbyusername(byval username string) integer?     dim userid integer?     dim conn sqlconnection = new sqlconnection(system.configuration.configurationmanager.connectionstrings("defaultconnection").connectionstring)     dim cmd sqlcommand = new sqlcommand("select userid user_info username = @username", conn)     cmd.parameters.add(new sqlparameter("@username", system.data.sqldbtype.nvarchar))     cmd.parameters("@username").value = username     conn.open()     dim reader sqldatareader = cmd.executereader()     try         while reader.read             userid = reader(0)         end while             reader.close()     end try     conn.close()     return userid end function