"IQueryable" does not contain a definition for "OrderByDescending"

Question

Getting this error for the orderby parameter in where. I did this because earlier, if I didn’t define “people,” I would get an error when returning for people saying that the name “people” does not exist in this current context. How to fix it?

 public JsonResult PersonsList(string birthyear)
 {
     TutorialDBContext db = new TutorialDBContext();
     var NumericYear = Convert.ToInt32(birthyear);
     IQueryable people;

     if (birthyear == "All")
     {
          people = from m in db.persons
                   select m;

          people = people.OrderByDescending(s => s.birthdate);
     }
     else
     {
          people = from m in db.persons
                   where m.birthdate.Year >= NumericYear
                   where m.birthdate.Year <= (NumericYear + 9)
                   select m;
     }

     return Json(people, JsonRequestBehavior.AllowGet);
 }

Answer 1

Because there is no such method. There is one that accepts IQueryable<T>. Use

IQueryable<Person> people;

or any type of item will be suitable.

Answer 2

OrderByDescending()is an extension method , not a general one . IQueryable<T>IQueryable

, people IQueryable<Person>.

Answer 3

people IQueryable<Person> - , people. , :

var people = from m in db.persons
             select m;
if (birthyear == "All")
{
    people = people.OrderByDescending(s => s.birthdate);
}
else
{
     people = people.Where(p => p.birthdate.Year >= NumericYear
                             && p.birthdate.Year <= NumericYear + 9)
}

Answer 4

• using System.Linq; .
• IQueryable people; IQueryable<Person> people;
• All birthyear , , var NumericYear = Convert.ToInt32(birthyear);

• public JsonResult PersonsList(string birthyear)
  {
      using (var db = new TutorialDBContext())
      {
          IQueryable<Person> people;
  
          if (birthyear == "All")
          {
              people = db.persons.OrderByDescending(s => s.birthdate);
          }
          else
          {
              var NumericYear = Convert.ToInt32(birthyear);
              people = from m in db.persons
                  where m.birthdate.Year >= NumericYear
                  where m.birthdate.Year <= (NumericYear + 9)
                  select m;
          }
  
          return Json(people, JsonRequestBehavior.AllowGet);
      }
  }