IEnumerable<T> to Dictionary<string, IEnumerable<T>> using LINQ

Having IEnumerable<Order> orders, how to get a Dictionary<string, IEnumerable<Order>> using Linq, where the key is Order.CustomerName mapped to a IEnumerable of customer's orders.

orders.ToDictionary(order => order.CustomerName) is not going to work right away, since there could be multiple orders that could have the same CustomerName.

Solution: orders.ToLookup(order => order.CustomerName);