Question

I read somewhere that view model properties must be only of strings.
e.g.

class PersonViewModel
{
   public string Number {get;set;}
   public string FullName {get;set;}
   public string Birthday {get;set;}
}

How can I do validation of this model as easily as using ValidationAttributes
and ModelState.IsValid method in ‘normal’ model?

UPD:
I use AutoMapper to map ViewModel to this Domain Model:

class Person
{
   public int ID {get;set;}
   public string FullName {get;set;}
   public DateTime Birthday {get;set;}
}

Answer 1

No, thats not true. With model binding, MVC will take care of it.

Here is a tutorial.

http://www.asp.net/mvc/tutorials/validation-with-the-data-annotation-validators-cs