Linq 之 GroupBy 方法实战（代码）练习

直接贴代码了：

namespace ConAppTempTest
{
    public class Customer
    {
        public int Id { get; set; }

        public string Name { get; set; }

        public DateTime Birthday { get; set; }

        public int WorkAge { get; set; }
    }

    public class CustomerDAL
    {
        public static IList<Customer> GetAllCustomers()
        {
            return new List<Customer>()
            {
                new Customer() { Id = 1, Name = "张三", Birthday = new DateTime(1981,3,3), WorkAge = 2 },
                new Customer() { Id = 2, Name = "李四", Birthday = new DateTime(1982,4,3), WorkAge = 3 },
                new Customer() { Id = 3, Name = "王五", Birthday = new DateTime(1983,5,3), WorkAge = 4 },
                new Customer() { Id = 4, Name = "赵六", Birthday = new DateTime(1984,6,3), WorkAge = 2 },
                new Customer() { Id = 5, Name = "杨七", Birthday = new DateTime(1985,7,3), WorkAge = 3 },
            };
        }
    }
}

 

        public static void Main(string[] args)
        {
            // GroupBy 下一个重载
            IEnumerable<IGrouping<int, string>> query2 = names.GroupBy(n => n.Length);
            Console.WriteLine("======================================================");
            foreach (IGrouping<int, string> groupItem in query2)
            {
                Console.Write("分组项 {0} 对应的元素有：", groupItem.Key);
                foreach (string elementItem in groupItem)
                {
                    Console.Write(elementItem + ",");
                }
                Console.WriteLine();
            }

            // GroupBy 下一个重载

            Console.WriteLine("======================================================");
            IList<Customer> customers = CustomerDAL.GetAllCustomers();
            var query3 = customers.GroupBy<Customer, int, string>(c => c.WorkAge, c => c.Name);
            foreach (var groupItem in query3)
            {
                Console.Write("分组项“工龄”为 {0} 对应的员工姓名有：", groupItem.Key);
                foreach (string elementItem in groupItem)
                {
                    Console.Write(elementItem + ",");
                }
                Console.WriteLine();
            }

            // GroupBy 下一个重载
            
            Console.WriteLine("======================================================");
            IEnumerable<DateTime> query4 = customers.GroupBy<Customer, int, DateTime>(c => c.WorkAge, 
                (int groupKey, IEnumerable<Customer> items) => 
                    new DateTime(DateTime.Now.Year, groupKey, items.Count() + 3)
           );
            Print(query4);
            
            
            // GroupBy 下一个重载
            
            Console.WriteLine("======================================================");
            IEnumerable<DateTime> query5 = customers.GroupBy<Customer, int, string, DateTime>(c => c.WorkAge,
                c => c.Name,
                (int groupKey, IEnumerable<string> itemNames) =>
                    itemNames.Count() > 1 ? 
                    new DateTime(DateTime.Now.Year, groupKey, itemNames.Count())
                    : new DateTime(DateTime.Now.Year, groupKey, itemNames.Count() + 5)
           );
            Print(query5);
        }

 

 

运行结果：

谢谢浏览！