c# Linq 及其扩展方法的使用

 public class LinqShow
    {
        /// 
        /// Linq to object(数组、集合）--内存里面的数据
        /// Linq to sql(查询数据库用的）--在数据库数据
        /// Linq XML查询XML文件
        /// 
        List studentsList = new List()
        {
            new Students
            {
                Id=1,
                Name="喜刷刷",
                ClassId=2,
                Age=22
            },
            new Students
            {
                Id=2,
                Name="喜刷刷2",
                ClassId=2,
                Age=22
            },
            new Students
            {
                Id=3,
                Name="喜刷刷3",
                ClassId=2,
                Age=22
            },
            new Students
            {
                Id=4,
                Name="喜刷刷4",
                ClassId=2,
                Age=22
            },
            new Students
            {
                Id=5,
                Name="喜刷刷3",
                ClassId=2,
                Age=22
            }
        };
 
 
        List stuClasses = new List
        {
            new StuClass
            {
                ID=1,
                Name="111"
            },
            new StuClass
            {
                ID=2,
                Name="222"
            },
            new StuClass
            {
                ID=3,
                Name="333"
            },
            new StuClass
            {
                ID=4,
                Name="444"
            }
        };
 
 
        public void Show()
        {
            List list = new List();
            #region
            foreach (var item in studentsList)
            {
                if (item.ClassId == 2)
                {
                    list.Add(item);
                }
            }
            //自定义Linq
            list = AntWhere(studentsList, s => s.Age < 23);
            //官方Linq
            var list4 = studentsList.Where(s => s.Age < 23);
            //自定义扩展Linq
            var list7 = studentsList.AntWhere(s => s.Age < 23);
            //表达式方法(匿名类)将查询的结果一新的匿名类返回 
            var list5 = from s in studentsList
                        where s.Age == 22
                        select new
                        {
                            Name = s.Name
                        };
            var list6 = studentsList.Join(stuClasses, s => s.ClassId, c => c.ID, (s, c) => new
            {
                ID = c.ID,
                Name = c.Name
            });
            #endregion
 
            //EF框架简单使用
 
            OAEntities db = new OAEntities();
            var userInfoList = db.UserInfo.Where(s => s.ID > 1);
            
            foreach (var item in userInfoList)
            {
                Console.WriteLine(item.Remark);  
            }
        }
 
        /// 
        /// Func Students委托形参，bool委托返回值类型
        /// 
        /// 
        /// 
        /// 
        public ListAntWhere(List resource,Funcbool>where)
        {
            List list = new List();
            foreach (var item in resource)
            {
                if (where.Invoke(item))
                {
                    list.Add(item);
                }
            }
            return list;
        }
 
            
    }
 
    /// 
    /// 自定义扩展Linq方法
    /// 
    public static class LinqExtend
    {
        public static IEnumerable<T> AntWhere<T>(this IEnumerable resource, Funcbool> where)
        {
            List list = new List(); 
            foreach (var item in resource)
            {
                if (where.Invoke(item))
                {
                    list.Add(item);
                }
            }
            return list;
        }
    }