Lambda&Linq

var list = new List<Model>
            {
                new Model { Id = 1, UserName = "张三", Password = "123456", Email = "zhang3@yoy.com"},
                new Model { Id = 2, UserName = "李四", Password = "234561", Email = "li4@yoy.com"},
                new Model { Id = 3, UserName = "王五", Password = "345612", Email = "wang5@yoy.com"},
                new Model { Id = 4, UserName = "赵六", Password = "456123", Email = "zhao6@yoy.com"},
            };

            //Add()：添加单个,新加的数据将会在列表的最末端
            //直译：添加
            list.Add(new Model { Id = 5, UserName = "孙七", Password = "561234", Email = "sun7@yoy.com"});
            //AddRange()：添加多个,新加的数据将会在列表的最末端
            //直译：范围添加
            list.AddRange(new List<Model>
            {
                new Model { Id = 6, UserName = "刘一", Password = "612345", Email = "liu1@yoy.com"},
                new Model { Id = 7, UserName = "陈二", Password = "654321", Email = "chen2@yoy.com"},
            });
            //Insert()：添加单个,新加的数据将会在指定的索引位置，用法与Add()类似
            //InsertRange()：添加多个,新加的数据将会在指定的索引位置，AddRange()类似
            //能指定位置插入数据，但是开销要大于Add/AddRange，目标集合越大，开销就越大
            list.Insert(3, new Model { Id = 8, UserName = "周八", Password = "111111", Email = "zhou8@yoy.com" });
            list.InsertRange(3, new List<Model>
            {
                new Model { Id = 9, UserName = "吴九", Password = "222222", Email = "wu9@yoy.com"},
                new Model { Id = 10, UserName = "郑十", Password = "333333", Email = "zheng10@yoy.com"},
            });

            //将集合转化为指定的类型
            var enumerable = list.AsEnumerable();//IEnumerable<T>类型
            var queryable = list.AsQueryable();//IQueryable<T>类型
                                               //IEnumerable类型内存迭代，
                                               //IQueryable类型表达式解析，语法树动态解析，延后查询
                                               //AsQueryable()常用于存在不确定的查询条件之前

            //Distinct()：去重复，与sql中distinct相同，返回值为IEnumerable<T>类型
            list = list.Distinct().ToList();

            //ForEach()：循环方法，括号中并非添加bool条件，而是进行操作
            list.ForEach(f => f.Id += 1);
            list.ForEach(f =>
            {
                if (f.Id == 7) f.Password = "1234567";
                else f.Id -= 1;
            });                    

            //Find()：Find一类方法为Framework2.0时期的产物，现基本不用
            var find = list.Find(f => f.Id == 1);
            var findAll = list.FindAll(f => f.Id == 1);

            //FirstOrDefault()：第一个或者是默认值，返回值肯能为null
            //Framework3.5时期的产物，运用范围更广，支持IEnemerable<T>，但速度比Find较慢
            //First()：与FirstOrDefault()用法相似，但不会返回null，而抛出异常
            var first = list.First();
            var firstOrDefault = list.FirstOrDefault();
            //最后一个，原理同First()/FirstOrDefault()
            var last = list.Last();
            var lastOrDefault = list.LastOrDefault();
            //唯一的一个，原理同First()/FirstOrDefault()，但如果出现重复数据，则抛异常
            var single = list.Single(s => s.Id == 2);
            var singleOrDefault = list.SingleOrDefault(s => s.Id == 7);

            var newList = new List<NewModel>
            {
                new NewModel { UserId = 2, Address = "Address", CellPhone = "1383838438", Country = "中国"},
                new NewModel { UserId = 3, Address = "Address", CellPhone = "1383838438", Country = "西班牙"},
                new NewModel { UserId = 4, Address = "Address1", CellPhone = "1383838438", Country = "中国"},
                new NewModel { UserId = 5, Address = "Address2", CellPhone = "1383838438", Country = "美国"},
            };
            //Join()：关联，相当于sql中的inner join
            //写法：第一集合.Join(第二集合,第一的关联值,第二的关联值,(第一集合名,第二集合名)=>查询结果)
            //查询结果可自定义类型，返回值为IEnemerable<查询结果>
            var joinInfo = list.Join(newList, l => l.Id, nl => nl.UserId, (l, nl) => new { l, nl }).ToList();
            var joinLinq = (from l in list
                            join nl in newList on l.Id equals nl.UserId
                            select new { l, nl }).ToList();

            //GroupBy()：按照指定参数进行分组,返回值类型为IEnemerable<IGrouping<string,T>>
            var groupInfo = newList.GroupBy(g => g.Country).ToList();
            var groupLinq = (from nl in newList
                             group nl by nl.Country into nlGroup
                             select nlGroup);
                            
            //GroupJoin()：左关联，相当于sql中的left join后进行了一定的分组，等于主表.Join(子表.GroupBy())
            //按照一定规律分组后进行关联，形成一对多的匿名类型,IEnemerable<{T1, IEnemerable<T2>}>
            //写法与Join相同：第一集合.GroupJoin(第二集合,第一的关联值,第二的关联值,(第一集合名,第二集合名)=>查询结果)
            //查询结果可自定义类型，返回值为IEnemerable<查询结果>
            //第一集合为主集合，第二集合为子集合，子集合条数可能为0
            var groupJoin = list.GroupJoin(newList, l => l.Id, g => g.UserId, (l, g) => new { l, g }).ToList();
            var groupJoinLinq = (from l in list
                             join nl in newList on l.Id equals nl.UserId into g
                             select new { l, g }).ToList();

            //DefaultIfEmpty()：查询默认或空实体，返回值为IEnumerable<T>类型，常用于做关联
            var defaultList = list.DefaultIfEmpty().ToList();

            //左关联变形：Join()/GroupJoin()加DefaultIfEmpty()方法实现
            //先将两集合进行GroupJoin()，之后将查询结果中的子集合DefaultIfEmpty()
            //注：此处的做关联与sql中的左关联有所不同，此处的左关联为一对一或一对null
            var leftJoin = list.GroupJoin(newList, l => l.Id, g => g.UserId, (l, g) => new { l, g = g.DefaultIfEmpty() }).ToList();
            var leftLinq1 = (from l in list
                             join nl in newList on l.Id equals nl.UserId into g
                             select new { l, g = g.DefaultIfEmpty() });
            var leftLinq2 = (from l in list
                            join nl in newList on l.Id equals nl.UserId into nlJoin
                            from g in nlJoin.DefaultIfEmpty()
                            select new { l, g });

            //All()：集合中的数据是否全部符合条件
            //直译：全部
            var trueAll = list.All(a => a.Id > 0);
            var falseAll = list.All(a => a.Id > 1);

            //Any()：集合中是否含有符合条件的数据
            //直译：存在
            var trueAny = list.Any(a => a.Id == 7);
            var falseAny = list.Any(a => a.Id == 11);

            //Min()/Max()：最小值/最大值
            //筛选出指定值/指定算法为最小/最大的数据，返回单条
            //可与左关联/排序等活用
            var minList = list.Min(m => m.Id);
            var maxList = list.Max(m => m.Email.Length);

            //OrderBy()/OrderByDescending()：正序/逆序
            //按照指定字段/指定算法进行正序/逆序的排序
            //可与左关联、分页等活用
            var orderBy = list.OrderBy(o => o.Id).ToList();
            var orderByLinq = (from l in list
                               orderby l.Id
                               select l).ToList();
            var orderByDesc = list.OrderByDescending(o => o.Email.Length);
            var orderByDescLinq = (from l in list
                                   orderby l.Email.Length descending
                                   select l).ToList();
            //Reverse()：反转排序，List无法适用
            var reverse = list.Where(w => true).Reverse().ToList();

            //Select()：将一个实体中的数据转为另一个实体
            //返回值类型为：IEnumerable<T>
            var select1 = list.Select(s => s.Id).ToList();//指定字段/值
            var select2 = list.Select(s => new { s.UserName, UserEmail = s.Email }).ToList();//匿名类型
            var select3 = list.Select(s => new UserInfo { UserId = s.Id, UserName = s.UserName, UserEmail = s.Email }).ToList();
            var select1Linq = (from l in list
                               select l.Id).ToList();
            var select2Linq = (from l in list
                               select new { l.UserName, UserEmail = l.Email }).ToList();
            var select3Linq = (from l in list
                               select new UserInfo { UserId = l.Id, UserName = l.UserName, UserEmail = l.Email }).ToList();
            //SelectMany()：查询出指定实体中的指定子集
            var selectMany = groupJoin.SelectMany(s => s.g).ToList();
            var country1 = groupJoin.SelectMany(s => s.g).Select(s => s.Country).ToList();
            var country2 = groupJoin.Select(s => s.g.Select(ss => ss.Country)).ToList();

            //Skip()：跳过指定个数，常用于分页等
            var skip = select1.Skip(1);
            //Take()：获取指定个数，常用于分页等
            var take = select1.Take(1);
            //SkipWhile()：跳过值，直到符合条件为止，按序跳过，当符合条件开始获取剩余的
            //直译：跳过直到
            var skipWhile1 = select1.SkipWhile(w => w < 9).ToList();
            var skipWhile2 = select1.SkipWhile(w => w == 1).ToList();
            //TakeWhile()：获取值，直到符合条件为止，按序获取，从第一条获取，当不符合条件则跳出
            //直译：获取直到
            var takeWhile1 = select1.TakeWhile(w => w < 10).ToList();
            var takeWhile2 = select1.TakeWhile(w => w == 1).ToList();

            //Sum()：求和，指定值的和，与sql中的功能相同
            var sum = list.Sum(s => s.Id);
            //Union()：追加数据，与sql中的功能相同
            var doubleList = select1.Union(skip).ToList();
            //Where()：查询条件，与sql中的功能相同
            var where = select1.Where(w => w > 5).ToList(); ;
            
            //删除指定数据
            //Remove()：删除指定数据，参数为数据类型
            //RemoveAt()：删除指定索引位置的数据
            //RemoveRange()：批量删除指定索引位置的数据(索引位置,  删除个数)
            //RemoveAll()：删除全部符合条件的数据
            list.Remove(firstOrDefault);
            list.RemoveAt(2);
            list.RemoveRange(3, 2);
            list.RemoveAll(r => r.Id > 4);


            var test = from l in list
                       join nl in newList on l.Id equals nl.UserId
                       let x = l.Password
                       select new { x, nl };

            Console.ReadKey();