c# - Razor Form Model - One of two properties mandatory -

i know following not possible, there similar way achieve 1 of 2 properties has filled out? in other words, user has enter either username or email.

public class logonmodel {     [required(orfield=email)]     [display(name = "user name")]     public string username { get; set; }      [required(orfield=username)]     [display(name = "email")]     public string email{ get; set; }      [required]     [datatype(datatype.password)]     [display(name = "password")]     public string password { get; set; }      [display(name = "remember me?")]     public bool rememberme { get; set; } } 

you write custom model validation attribute, optionally client-side adapter make javascript validate things, or handle in controller code:

public actionresult logon(logonmodel model) {     if(string.isnullorwhitespace(model.username) &&         string.isnullorwhitespace(model.email))      {         modelstate.addmodelerror("username", "either username or email must provided.");     }     if(modelstate.isvalid) {...}     else {...} } 

in particular case, more elegant solution may accept either email or username in username field, , intelligently detect 1 user provided.