using System;

namespace StringSol
{
    internal class Program
    {
        static void Main(string[] args)
        {
            var name = "Yu Hsiang";
            string str1 = "你好" + name;
            string str2 = String.Concat("你好", name);
            string str3 = String.Format("你好{0}", name);
            // $是c# 6.0 的語言特性，功能類似string.format()
            string str4 = $"你好{name}";

            Console.WriteLine(str1);
            Console.WriteLine(str2);
            Console.WriteLine(str3);
            Console.WriteLine(str4);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;

namespace linq_groupby
{
    internal class Program
    {
        public class Student
        {
            /// <summary>
            /// 編號
            /// </summary>
            public int Id { get; set; }

            /// <summary>
            /// 姓名
            /// </summary>
            public string Name { get; set; }

            /// <summary>
            /// 教室
            /// </summary>
            public char Classroom { get; set; }
        }

        static void Main(string[] args)
        {
            var students = new List<Student>
            {
                new Student {Id = 1, Name = "大雄",Classroom = 'A'},
                new Student {Id = 2, Name = "多拉A夢",Classroom = 'B'},
                new Student {Id = 3, Name = "胖虎",Classroom = 'A'},
            };
            var classRoomGroup = students
                .GroupBy(x => x.Classroom)
                .Select(x => new
                {
                    ClassRoom = x.Key,
                    StudentCount = x.Count(),
                }).ToList();

            foreach (var item in classRoomGroup)
            {
                Console.WriteLine($"Classroom:{item.ClassRoom} - StudentCount:{item.StudentCount}");
            }
        }
    }
}

public static System.Collections.Generic.IEnumerable<TResult> 
Join<TOuter,TInner,TKey,TResult> (
    this System.Collections.Generic.IEnumerable<TOuter> outer,
    System.Collections.Generic.IEnumerable<TInner> inner, 
    Func<TOuter,TKey> outerKeySelector, 
    Func<TInner,TKey> innerKeySelector,
    Func<TOuter,TInner,TResult> resultSelector, 
    System.Collections.Generic.IEqualityComparer<TKey>? comparer);

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace JoinSample
{

    public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

    public class UserDetail
    {
        public int UserId { get; set; }
        public string PhoneNumber { get; set; }
    }


    public class UserData
    {
        public int Id { get; set; }

        public string UserName { get; set; }
        public string PhoneNumber { get; set; }
    }

    internal class Program
    {
        static void Main(string[] args)
        {
            var users = new List<User>
            {
                new User
                {
                    Id =1,Name="大雄",
                },
                new User
                {
                    Id =2,Name="多拉A夢",
                },
                new User
                {
                    Id =3,Name="胖虎",
                },
                new User
                {
                    Id =4,Name="小夫",
                }
            };

            var userDetails = new List<UserDetail> {
                new UserDetail{ UserId=1,PhoneNumber="0911111111"},
                new UserDetail{ UserId=2,PhoneNumber="0922222222"}
            };

            var userData = users.Join(
                userDetails,
                x => x.Id,
                y => y.UserId,
                (x, y) => new UserData
                {
                    Id = x.Id,
                    PhoneNumber = y.PhoneNumber,
                    UserName = x.Name
                });

            foreach (var item in userData)
            {
                Console.WriteLine(item.Id);
                Console.WriteLine(item.UserName);
                Console.WriteLine(item.PhoneNumber);
            }
        }
    }
}

var endlessTask = Task.Run(async () =>
    {
        while (true)
        {
          // Todo
        }
    });

using System;
using System.Threading.Tasks;

namespace EndlessTaskAsync
{
    class Program
    {
        /// <summary>
        /// 主程式
        /// </summary>
        /// <returns></returns>
        public static async Task Main()
        {
            var endlessTask1 = EndlessTask(1);
            var endlessTask2 = EndlessTask(2);

            await PreventToStop();
        }

        /// <summary>
        /// 製作無止盡的 while task
        /// </summary>
        /// <param name="number">編號</param>
        /// <returns></returns>
        private static Task EndlessTask(int number)
        {
            Console.WriteLine("Start EndlessTask" + number);
            var endlessTask = Task.Run(async () =>
            {
                while (true)
                {
                    Console.WriteLine("EndlessTask" + number);
                    await Task.Delay(100);
                }
            });
            return Task.CompletedTask;
        }

        /// <summary>
        /// 避免視窗關閉，使用ReadKey();
        /// </summary>
        /// <returns></returns>
        private static Task PreventToStop()
        {
            Console.ReadKey();
            return Task.CompletedTask;
        }
    }
}