C＃-Linq to SQL-通过嵌套类的元素对列表进行排序

Question

I am using Linq to SQL in a WebApi to return a list of objects from a database to a frontend.

Let's say the model looks something like this:

public class Course
{
    public int ID { get; set; }
    public string NAME { get; set; }       
}
public class Schedules
{
    public int id { get; set; }
    public int courseid
    public datetime start { get; set; }
} 

In addition my Linq-to-SQL inside of one Controller looks something like this:

...
...
var list =    (from xx in xx.Courses
              select new Course
              {
                  ID = xx.ID,
                  NAME = xx.NAME,
                  Schedules = (from yy in yy.Schedules
                              where xx.ID == yy.courseid
                              select new Schedules
                              {
                                 id = yy.id,
                                 courseid = yy.courseid,
                                 start = yy.start
                              }).toList()
              }).toList()
              ...
              ...

Now I need to order "list" by the minValue of Schedules.start in an ascending order. That means, that the output should give me the element with the earliest start first. In addition Courses with no planned schedule should be given out at the end.

In the end the output should look like this:

[{"ID":5, "NAME":"NAME1", "Schedules":[{"id":10, "courseid":5, "start":" 2017-12-15 00:00:00.000 "}, {"id":8, "courseid":5, "start":" 2017-12-20 00:00:00.000 "}]}],[{"ID":1, "NAME":"NAME1", "Schedules":[{"id":9, "courseid":1, "start":" 2017-12-16 00:00:00.000 "}, {"id":2, "courseid":1, "start":" 2017-12-17 00:00:00.000 "}]}]

Thanks in advance.

Answer 1

I was in such a situation where I need to sort the parent depend on the child property's value.

var list =    (from xx in xx.Courses
              select new Course
              {
                  ID = xx.ID,
                  NAME = xx.NAME,
                  Schedules = (from yy in yy.Schedules
                              where xx.ID == yy.courseid
                              select new Schedules
                              {
                                 id = yy.id,
                                 courseid = yy.courseid,
                                 start = yy.start
                              }).toList()
              }).OrderBy(mc => mc.Schedules.Min(dc => dc.start)).toList()