LINQ投影操作符Select与限制操作符where介绍

public class Employees
{
        public Guid Id { get; set; }
        public string Name { get; set; }
        public int Sex { get; set; }
        public string CompanyName { get; set; }
}

class Program
{
        static void Main(string[] args)
        {
            //使用集合初始化器给集合赋值
            List<Employees> emp = new List<Employees> 
            { 
               new Employees(){Id=Guid.NewGuid(),Name="张三",Sex=0,CompanyName="xx技术有限公司"},
               new Employees(){Id=Guid.NewGuid(),Name="李四",Sex=0,CompanyName="xx培训"},
               new Employees(){Id=Guid.NewGuid(),Name="王五",Sex=0,CompanyName="xx集团"}
            };

            //查询语法：不能省略最后的select
            var query = (from p in emp where p.Name.StartsWith("王") select p).FirstOrDefault();

            //查询方法:设计到Lambda表达式，全部返回 可以省略最后的select 延迟加载
            var query1 = emp.Where(p => p.Name.StartsWith("王")).Select(e => new { e.Name,e.CompanyName});

            //查询方法:返回匿名类
            var query2 = emp.Where(p => p.Name.StartsWith("王")).Select(p => p);
            foreach (var item in query1)
            {
                Console.WriteLine(item.Name);
            }
            Console.ReadKey();
        }
}

//where限制操作符：使用延迟加载
var q = teachers.SelectMany(p => p.Students).Where(s => s.Score < 60).Select(a => new { name = a.Name });
foreach (var item in q)
{
     Console.WriteLine("姓名:"+item.name);
}