1 int[] nums = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 2 IEnumerable<int> newNums = from n in nums where n > 0 select n; 3 newNums = newNums.Where(new Func<int,int, bool>(delegate(int i,int index) { return i < index; })); 4 newNums = newNums.Where(new Func<int, int, bool>((int i, int index)=> i < index)); 5 newNums = newNums.Where(delegate(int i, int index) { return i < index; }); 6 newNums = newNums.Where((i, index) => i < index); 7 foreach (var i in newNums) 8 { 9 Console.WriteLine(i);10 }二.集合操作，也可适于到EF的数据库操作
1.创建两个实体类
1 public class Store 2 { 3 public string Id; 4 public string Name; 5 } 6 public class Person 7 { 8 public string name { get; set; } 9 public int age { get; set; }10 public string StoreId { get; set; }11 }2.插入数据
1 var Stores = new List<Store>() 2 { 3 new Store() { Id=1,Name=1班}, 4 new Store() { Id=2,Name=2班} 5 }; 6 7 var Persons = new List<Person>() 8 { 9 new Person() { name=p1,age=1, StoreId=1},10 new Person() { name=p2,age=2, StoreId=1},11 new Person() { name=p3,age=3, StoreId=1},12 new Person() { name=p4,age=4, StoreId=2},13 new Person() { name=p5,age=5, StoreId=1},14 new Person() { name=p6,age=6, StoreId=2},15 new Person() { name=p7,age=7, StoreId=1},16 new Person() { name=p8,age=8, StoreId=1}17 };3. 查询年龄小于3岁的人1班和2班分别有几个人
1 var plst = Persons.Where(o => o.age > 3).GroupBy(o => o.StoreId).Select(g => new { StoreId = g.Key, Count = g.Count() }).Join(Stores, s => s.StoreId, p => p.Id, (s, p) => new { s.StoreId, storeName = p.Name, s.Count });2 foreach (var p in plst)3 {4 Console.WriteLine(p.storeName + 有 + p.Count + 个人);5 }4.输出
2班有2个人 1班有3个人
