public class LinqShow{/// <summary>/// 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/// </summary>List<Students> studentsList = new List<Students>(){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<StuClass> stuClasses = new List<StuClass>{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<Students> list = new List<Students>();#regionforeach (var item in studentsList){if (item.ClassId == 2){list.Add(item);}}//自定义Linqlist = AntWhere(studentsList, s => s.Age < 23);//官方Linqvar list4 = studentsList.Where(s => s.Age < 23);//自定义扩展Linqvar 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 studentsListwhere s.Age == 22select 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);  }}/// <summary>/// Func<Students,bool> Students委托形参，bool委托返回值类型/// </summary>/// <param name="resource"></param>/// <param name="where"></param>/// <returns></returns>public List<Students>AntWhere(List<Students> resource,Func<Students,bool>where){List<Students> list = new List<Students>();foreach (var item in resource){if (where.Invoke(item)){list.Add(item);}}return list;}}/// <summary>/// 自定义扩展Linq方法/// </summary>public static class LinqExtend{public static IEnumerable<T> AntWhere<T>(this IEnumerable<T> resource, Func<T, bool> where){List<T> list = new List<T>(); foreach (var item in resource){if (where.Invoke(item)){list.Add(item);}}return list;}}