Server Side Validations in MVC4 Models

public partial class NormalRegistration

{

public int Id { get; set; }

[RegularExpression(@"^[a-zA-Z''-'\s]*$", ErrorMessage = "Please Enter valid Name")]

[Required]

[StringLength(50)]

public string Name { get; set; }

[Required(ErrorMessage = "Email_id must not be empty")]

[RegularExpression(".+\\@.+\\..+", ErrorMessage = "Please Enter valid mail id")]

public string Email { get; set; }
}

I am writing validations in models in mvc4 ,i am using regular expressions also.some times are working and sometimes are not working.can you please tell me how to getrid of this problem?