private IEnumerable<Customer> GetCustomers() { return new List<Customer> { new Customer { Id = 1, Name = "John Smith" }, new Customer { Id = 2, Name = "Mary Williams" } }; } 

vs

 IList<Customer> customers=new List<Customer> { new Customer { Id=1,Name="john Smith"}, new Customer { Id = 2,Name = "Mary Williams"} }; 

whats the difference btw these two.