asp.net mvc - in mvc [required]attribute errormessages for string variable alone im getting customerrormessges but not for bool ,datetime,int -

my code like

public class user {      [required(errormessage = "please enter username")]     public string username { get; set; }

for string property im getting error message properly. but...

    [required(errormessage = "please enter dateof birth")]     public datetime dob { get; set; }

for im getting default model state validator message im getting like:

"required property 'datetime' not found in json. path '', line 5, position 2".

i want here "please enter dateof birth" .message im unable ..for bool or datetime or int im unble can on .thanks in advance

i going take guess trying assign null dob. datetime not nullable, can allow nulls changing follows:

[required(errormessage = "please enter dateof birth")] public datetime? dob { get; set; }

this works int? , bool? too

Macro