public static event Func<Student, bool> myevent;

        public delegate void del(int i, int j);

        static void Main(string[] args)

        {

            var students = new List<Student> {

              new Student(){ Id=, Age=, Name="张三1", Sex=true   , GradeId=},

              new Student(){ Id=, Age=, Name="李四1", Sex= false , GradeId=},

              new Student(){ Id=, Age=, Name="王二", Sex= false , GradeId=},

              new Student(){ Id=, Age=, Name="赵六", Sex=true   , GradeId=},

            };

            // BookShopPlus2Entities db = new BookShopPlus2Entities();

            //AsNoTracking查询的对象不要放在对象池中

            //特别说明：对于使用AsNoTracking（）的数据不能用于修改。

            //List<Book> db = bsc.Books.AsNoTracking().ToList();

            //del mydel = new del(add);

            //mydel.Invoke(1, 9);

            //// //匿名方法

            //mydel += delegate(int h, int m)

            //{

            //};

            ////Lamda表达式

            //mydel += (a, b) =>

            //{

            //    Console.WriteLine(a + b);

            //};

            //生成 1==1

            Expression expwhere = Expression.Equal(Expression.Constant(), Expression.Constant());

            //生成 s=>

            ParameterExpression exps = Expression.Parameter(typeof(Student), "s");

            //生成s.Age>12

            Expression exp1 = Expression.GreaterThan(Expression.Property(exps, "Age"), Expression.Constant());

            //生成s.Age<22

            Expression exp2 = Expression.LessThan(Expression.Property(exps, "Age"), Expression.Constant());

            //生成 s.Age>12 and  s.Age<22  或连接 Expression.Or  and 连接   Expression.And

            Expression exp3 = Expression.And(exp1, exp2);

            //Expression<Func<Student, bool>> lamband = Expression.Lambda < Func<Student, bool>.Combine();

            //生成s=>Age>12 AND    s.Age<22

            Expression<Func<Student, bool>> lamband =

            Expression.Lambda<Func<Student, bool>>(exp3, exps);

            var s = students.Where(lamband.Compile()).ToList();

        }

    }

    public class Student

    {

        public int Id { get; set; } //学号

        public string Name { get; set; } //学员姓名

        public int Age { get; set; } //学生年龄

        public bool Sex { get; set; } //学生性别

        public int GradeId { get; set; }

    }