c# - ASP.NET OWIN use Email to Login (instead of username) -

currently, application owin authentication following way (using username & password, in code below). need make users log in using email (instead of username) , password.

as workaround, can find username email (entered user) , use current method (username + password), double database call, i'm trying avoid. please advise. thanks!

protected void login(object sender, eventargs e)         {             if (isvalid)             {                    var manager = new myusermanager(new myuserstore(new mydbcontext()));                  myuser user = manager.find(username.text, password.text);                  if (user != null)                 {                     identityhelper.signin(manager, user, rememberme.checked);                     identityhelper.redirecttoreturnurl(request.querystring["returnurl"], response);                 }                 else                 {                     failuretext.text = "invalid login";                     errormessage.visible = true;                 }             }         }