使用ILookup<TKey, TElement> 接口查找集合

public class Program
    {
        public static void Main()
        {
            // 创建一个放入ilookup数据结构的School清单。
            List<School> schools = new List<School> { new School { University = "西南交通大学",Address="成都"},
                                                 new School { University = "北京交通大学" ,Address="北京"},
                                                 new School { University = "西南政法大学" ,Address="重庆"},
                                                 new School { University = "北京航空航天大学" ,Address="北京"},
                                                 new School { University = "清华大学",Address="北京"} };

            // 创建一个查询来组织packages集合。使用大学的第一个字符作为关键值。
            //ILookup 对象中选择大学(University)附加大学地址(Address)作为每一个元素的值。
            ILookup<char, string> schoolLookup = schools.ToLookup(
                p => Convert.ToChar(p.University.Substring(0, 1)),
                p => p.University + " " +p.Address
                );

            // 在ilookup遍历和输出内容的每个值。
            foreach (var packageGroup in schoolLookup)
            {
                // 打印的关键值。
                Console.WriteLine(packageGroup.Key);
                // 遍历集合中的每个值。
                foreach (string str in packageGroup)
                    Console.WriteLine("    {0}", str);
            }
        }
    }
    class School
    {
        public string University { get; set; }
        public string Address { get; set; }
    }