Question

如何在Entity Framework中使用lambda表达式进行查询？

select 
    s.StudentID, s.StudentName, s.StudentSurName, s.Point 
from 
    Student s
join 
    StudentContest sc on s.StudentID = sc.StudentId
join 
    Contest c on c.ContextID = sc.ContestId 
where 
    c.ContextDate < GETDATE()

Answer 1

我基于类制作了一个模型以显示结果

   class Program
    {
        static void Main(string[] args)
        {
            DateTime date = DateTime.Now;
            DataBase db = new DataBase();

            var results = (from s in db.Student
                           join sc in db.StudentContest on s.StudentID equals sc.StudentId
                           join c in db.Contest.Where(x => x.ContextDate < date) on sc.ContextID equals c.ContestId
                           select new { StudentID = s.StudentID, StudentName = s.StudentName, StudentSurName = s.StudentSurName, Point = s.Point }
                           ).ToList();
        }
    }
    public class DataBase
    {
        public List<StudentContest> StudentContest { get; set; }
        public List<Student> Student { get; set; }
        public List<Contest> Contest { get; set; }
    }
    public class StudentContest
    {
        public string StudentId { get; set;}
        public string ContextID { get; set;}
    }
    public class Student
    {
        public string StudentID { get; set;}
        public string StudentName { get; set;}
        public string StudentSurName { get; set;}
        public string Point { get; set;}
    }
    public class Contest
    {
        public string ContestId { get; set;}
        public DateTime ContextDate { get; set; }
    }

如何将此SQL查询转换为Entity Framework lambda表达式？

1 个答案: