学习计划实践

 static void Main(string[] args)
        {
            #region MyRegion
            //添加数据
            //using (var db = new TestEFEntities())
            //{
            //    db.Students.Add(new Student
            //    {
            //        Name = "lv22",
            //        Sex = "2"
            //    });
            //    db.SaveChanges();
            //}

            ////查询
            //using (var s_select = new TestEFEntities())
            //{
            //    s_select.Database.Log = s => Console.WriteLine(s);
            //    var st = s_select.Students.First(s => s.Id == 6);
            //    //var m_student=  s_select.Students.Select(u=>new { id = u.Id ,name=u.Name,sex=u.Sex}).FirstOrDefault();
            //}

            //删除
            //using (var db = new TestEFEntities())
            //{
            //    //实例化一个对象，并指定ID的值
            //    var n = new Student() { Id = 4 };
            //    //将n对象附到上下文当中
            //    db.Students.Attach(n);
            //    //删除n对象
            //    db.Students.Remove(n);
            //    db.SaveChanges();
            //    Console.WriteLine("删除成功");

            //    //1.1 先根据id查询 出 要删除的 对象（存入EF容器）
            //    Student usr = db.Students.Where(u => u.Id == 1).FirstOrDefault();
            //    //1.2 将实体对象删除（就是将 容器中的 代理对象的 State改成 Deleted）
            //    db.Students.Remove(usr);
            //    //1.3 将EF容器里所有的对象 根据 State 属性值，生成不同sql语句，更新到数据库
            //    db.SaveChanges();
            //}

            //修改
            //using (var db = new TestEFEntities())
            //{
            //    Student u = new Student() {Id=5, Name = "kim", Sex = "1" };
            //    db.Entry(u).State = EntityState.Modified;
            //    db.SaveChanges();
            //    Console.WriteLine("修改成功");
            //}


            //修改
            //using (var db = new TestEFEntities())
            //{
            //    db.Database.Log = s => Debug.WriteLine(s);
            //    var query = db.Students.FirstOrDefault(s => s.Id == 5);
            //    if (query != null)
            //    {
            //        query.Name = "kim";
            //        query.Sex = "1";
            //        db.SaveChanges();
            //    }

            //    db.SaveChanges();
            //    Console.WriteLine("修改成功");
            //}

            //////分组
            //using (var db = new TestEFEntities())
            //{
            //    //.Select(m => m.Max(o => o.Id)
            //    db.Database.Log = s => Debug.WriteLine(s);
            //    //db.Database.Log = s => File.("a.txt",s);
            //    //List <Student> list = new List<Student>();
            //    var temp1 = db.Students.GroupBy(x => x.Name).Select(s=>s.Key).ToList();
            //    // db.SaveChanges();
            //    Console.WriteLine(temp1);
            //    Console.ReadKey();
            //}

            //模糊查询
            //using (var db=new TestEFEntities())
            //{
            //    db.Database.Log = s => Debug.WriteLine(s);
            //    var query = db.Students.Where(s => s.Name.Contains("k")).ToList();
            //}

            //排序
            //using (var db = new TestEFEntities())
            //{
            //    db.Database.Log = s => Debug.WriteLine(s);
            //    //var query = db.Students.OrderBy(s => s.Name).OrderByDescending(s=>s.Id).ToList();
            //    var query = db.Students.OrderBy(s => s.Id).ToList();
            //}

            //
            //using (var db = new TestEFEntities())
            //{
            //    db.Database.Log = s => Debug.WriteLine(s);
            //    var list2 =db.teachers.SelectMany(t => t.Student).Where(s => s < 60);
            //}


            //ForEach遍历
            //using (var db = new TestEFEntities())
            //{
            //    db.Database.Log = s => Debug.WriteLine(s);
            //    var _student = db.Students.ToList();
            //    // db.Students.ToList().ForEach(f => Console.WriteLine(f.Name));
            //    //_student.ForEach(s => {
            //    //    s.Name = "aaaa";
            //    //    s.Score = 89;
            //    //});
            //}

            //Console.ReadKey();


            //using (var db = new TestEFEntities())
            //{
            //    db.Database.Log = s => Debug.WriteLine(s);

            //    //返回多条符合结果的数据
            //    var st = db.Students.ToList().FindAll(s => s.Score >= 78);//find性能>where
            //    var st1 = db.Students.Where(s => s.Score >= 78).ToList();

            //    //返回-条符合结果的数据
            //    var ff = db.Students.ToList().Find(s=>s.Score>78);
            //    var ff2 = db.Students.FirstOrDefault(s => s.Score > 78);

            //    //检查后面条件是否成立，成立则返回true，否则返回false
            //    var ee = db.Students.ToList().Exists(s=>s.Score==62); 


            //   Console.WriteLine(ee);
            //}
            //Console.ReadKey();


            //删除多条符合条件的一批数据
            //using (var db = new TestEFEntities())
            //{
            //    db.Database.Log = s => Debug.WriteLine(s);
            //    //var n = new Student() { Id =( 1,2 )};
            //    //db.Students.Attach(n);

            //    var usr = db.Students.ToList().FindAll(s => s.Score >= 78);
            //    db.Students.RemoveRange(usr);
            //    db.SaveChanges();

            //    Console.WriteLine();
            //}
            //Console.ReadKey();


            //
            //using (var db = new TestEFEntities())
            //{
            //    db.Database.Log = s => Debug.WriteLine(s);
            //    //var stu = db.Students.ToList().FindAll(s => s.Name == "k");
            //    var stu = db.Students.ToList().RemoveAll(s => s.Id == 5);
            //    db.SaveChanges();
            //    Console.WriteLine(stu);
            //} 
            #endregion



            List<Student> students = new List<Student>();
            students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 90 });
            students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 78 });
            students.Add(new Student() { Name = "crank arm  80", Sex = "1", Score = 80 });
            students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 70 });
            students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 79 });
            students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 89 });
            students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 34 });
            students.Add(new Student() { Name = "crank arm12312", Sex = "1", Score = 78 });
            students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 56 });
            students.Add(new Student() { Name = "crank arm23432432", Sex = "1", Score = 78 });
            students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 40 });


            #region MyRegion
            //返回第一个符合条件的数组成员所在的位置
            // var index = students.FindIndex(s => s.Score == 78); 

            //返回符合条件的数组成员最后一个元素
            //var index = students.FindLast(s=>s.Score==78);

            //返回符合所定义的条件中成员最后一个匹配的项从零开始的索引
            //var index = students.FindLastIndex(s=>s.Score==90);

            //查找字符串首次出现的位置，返回索引值
            //string test = "az  fy";
            //Console.WriteLine(test.IndexOf("z"));

            //Insert在list里面插入一个实体，数据的位置由自己指定
            //students.Insert(10,new Student { Id=1,Name= "crank arm",Sex="1",Score=100 });
            //foreach (var item in students)
            //{
            //    Console.WriteLine(item.Id.ToString()+"    "+item.Name + "    " + item.Sex + "    " + item.Score);
            //}

            //对要查找的字符串从后往前查找，找到第一个匹配的位置
            //string test = "abcdefjjkk";
            //Console.WriteLine(test.LastIndexOf("j")); 

            //ToArray的使用是将一个集合转成一个数组返回集合里包含的所有元素
            //Student[] stu = students.ToArray();
            //Console.WriteLine(stu[9].Name);


            //数组转集合
            // int[] alist = new int[] { 23, 24, 29 };
            //List<int> sd = alist.ToList();
            // foreach (var item in sd)
            // {
            //     Console.WriteLine(item);
            // }
            #endregion

            #region MyRegion

            //foreach (var item in students)
            //{
            //    Console.WriteLine(item.Name + " ");
            //}

            //Console.WriteLine("----------------------------");

            //修改
            //students.ForEach(f =>
            //    {

            //        if (f.Score == 80)
            //        {
            //            f.Name = "则是一个";
            //            f.Sex = "2";
            //            f.Score = 99;
            //        }
            //    });

            //foreach (var item in students)
            //{
            //    Console.WriteLine(item.Name+" ");
            //}
            //Console.WriteLine(students);
            //Console.ReadKey();

            //RemoveAll删除
            //students.RemoveAll(f=>f.Score==40);

            //Remove删除
            //var delete = students.Find(s => s.Score == 56);
            //students.Remove(delete);

            //模糊查询
            // var stu= students.Where(s=>s.Name.Contains("80"));

            //OrderBy升序，OrderByDescending降序
            //var stu = students.OrderBy(s => s.Score).OrderByDescending(s=>s.Name).ToList();

            // First
            //var stu = students.First(s => s.Score == 80);
            //Console.WriteLine(stu.Score);

            // FirstOrDefault
            //var stu = students.Select(s => s.Score == 90).FirstOrDefault();
            //Console.WriteLine(stu); 
            #endregion

            //分组
            //var stu=students.GroupBy(s=>s.Score).ToList();
            //foreach (var item in stu)
            //{
            //    Console.WriteLine(item.Key);
            //}

            var ss = students.FindIndex(f => f.Score == 80);
            var sss = students.FindLast(f => f.Score == 80);
            var sd = students.FindLastIndex(f => f.Score == 80);

            Console.WriteLine(sd);
            foreach (var item in students)
            {
                Console.WriteLine(item);
            }
            Console.WriteLine("--------------------------------");

            Student[] st = students.ToArray();
            Console.WriteLine(st[0].Score);



            //RemoveRange时删除指定某一段索引的值
            //RemoveAt是删除指定索引的值
            // students.RemoveRange(1,3);
            //var st = students.ToList().FindAll(s => s.Score > 70);
            //students.RemoveAt(1);
            //RemoveAll是删除指定数据值
            //var st = students.RemoveAll(s => s.Score == 90);
            //foreach (var item in students)
            //{
            //    Console.WriteLine(item.Score);
            //}



            List<Student> m_students = new List<Student>();
            m_students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 1 });
            m_students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 1 });
            m_students.Add(new Student() { Name = "crank arm  80", Sex = "1", Score = 1 });
            m_students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 1 });
            m_students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 1 });
            m_students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 89 });
            m_students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 34 });
            m_students.Add(new Student() { Name = "crank arm12312", Sex = "1", Score = 78 });
            m_students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 56 });
            m_students.Add(new Student() { Name = "crank arm23432432", Sex = "1", Score = 78 });
            m_students.Add(new Student() { Name = "crank arm", Sex = "1", Score = 40 });


            //AddRange是添加到数组的末尾
            //students.AddRange(m_students);

            //Where是按指定条件查询，返回结果集，必须要加条件
            //select是按指定的条件查询，返回Bool类型
            //var s = students.Where(f => f.Name.Contains("80")).ToList();
            //var ss = students.Select(f => f.Name.Contains("32")).ToList();

            //Insert是指把添加插入到指定的序列
            // students.Insert(7, new Student { Name = "111111111111111111111", Sex = "3", Score = 100 });



            //foreach (var item in students)
            //{
            //    Console.WriteLine(item.Name + "     " + item.Sex + "            " + item.Score);
            //}

            Console.ReadKey();
        }