LINQ详细的介绍

//先定义一个类

 public   class StudentModel 
    {
      public   int index { get; set; }

        public string Name { get; set; }

        public string Sex { get; set; }
      
    }

//存一点测试数据

 List<StudentModel> modes = new List<StudentModel>(); 

            modes.Add(new StudentModel() { index=1, Name="a", Sex="女"});
            modes.Add(new StudentModel() { index = 2, Name = "b", Sex = "女" });
            modes.Add(new StudentModel() { index = 3, Name = "c", Sex = "男" });
            modes.Add(new StudentModel() { index = 4, Name = "d", Sex = "女" });
            modes.Add(new StudentModel() { index = 5, Name = "e", Sex = "男" });
            modes.Add(new StudentModel() { index = 5, Name = "f", Sex = "0.5" });
            modes.Add(new StudentModel() { index = 5, Name = "g", Sex = "0.5" });　　

//单条件查询
           var smlist = modes.Where(a => a.Sex == "男").ToList();
            foreach(StudentModel sm in smlist)
            {
                Console.WriteLine(sm.Name+":"+sm.Sex);
            }

//多条件查询或者
            var smlist1 = modes.Where(a => a.Sex == "男" || a.Sex.Contains("0.5")).ToList();
            foreach (StudentModel sm in smlist1)
            {
                Console.WriteLine(sm.Name + ":" + sm.Sex);
            }

 //多条件查询并且
            var smlist2 = modes.Where(a => a.Name == "f" && a.Sex.Contains("0.5")).ToList();
            foreach (StudentModel sm in smlist2)
            {
                Console.WriteLine(sm.Name + ":" + sm.Sex);
            }

//返回列表正序排列OrderBy，倒序排列OrderByDescending
            var smlist3 = modes.Where(a => a.Sex == "男").OrderBy(a=>a.Name).ToList();
            foreach (StudentModel sm in smlist3)
            {
                Console.WriteLine(sm.Name + ":" + sm.Sex);
            }

//distinct去重
            var smlist3 = modes.Where(a => a.Sex == "男").OrderBy(a=>a.Name).ToList().Distinct();
            foreach (StudentModel sm in smlist3)
            {
                Console.WriteLine(sm.Name + ":" + sm.Sex);
            }

//返回满足条件的第一个结果first,最后一个last 
            var  smlist3 = modes.Where(a => a.Sex == "男").First();
                Console.WriteLine(smlist3.Name + ":" + smlist3.Sex);