restrict class to create object

i have a Code structure like below :

namespace Same
{
 public class A
 {
	public string Name{get;set;}
	public B email{get;set;}
 }

 public class B
 {
	public string Email{get;set;}
 }
}

I need to allow only class A to create object but want to restrict Class B to create Object.

If have any solution then plz suggest me..

Thanks.

Ajay
ajaypatelfromsanthal.blogspot.in