How do I use OrderBy in my data on multiple fields?

Question

Here is my code:

void Main() {
    List<Restaurant> RestaurantData = new List<Restaurant>();
}

class Restaurant {
    public int Id;
    public List<Complaint> ComplaintsList = new List<Complaints>();
}

class Complaint {
    public string Name;
    public string Address;
    public int Age;
    public DateTime ComplaintDate;
}

RestaurantData.OrderBy( x => x.ID, y => y.Complaint.Name).ToList();

I get an error on the y => y.Complaint.Name part. Can someone please help me understand why?

I want to order the data by Restaurant ID, and then by the Name of the Complaint.

Answer 1

After your edit, it appears that you want to Order the List first based on Restaurant.Id and then you want to order the inner list of Complaint based on Name . Following should do it.

List<Restaurant> newListOfRestaurant
        = RestaurantData
             .OrderBy(x => x.Id)
             .Select(r => new Restaurant
                  {
                      Id = r.Id,
                      ComplaintsList = r.ComplaintsList
                                        .OrderBy(c => c.Name)
                                        .ToList()
                  })
              .ToList();

---

(Old Answer)

You need to use Enumerable.ThenBy if you want order on multiple fields.

Performs a subsequent ordering of the elements in a sequence in ascending order according to a key.

RestaurantData  = RestaurantData.OrderBy( x => x.ID)
                                .ThenBy(y => y.Complaint.Name)
                                .ToList();

You need to assign the result back to the RestaurantData , otherwise it will not modify the existing list.

Answer 2

OrderBy does not modify collection ! Use ThenBy for multi field sorting

RestaurantData = RestaurantData.OrderBy( x => x.ID)
                       .ThenBy(y => y.Complaint.Name).ToList();

OrderBy is returing IOrderedEnumerable, read more about OrderBy

Answer 3

The OrderBy only accepts a single property expression. To do multiple ones you must ThenBy() with other property expressions. Do,

 var restaurantsByIdThenByComplaintName = 
     RestaurantData
           .OrderBy(restaurant => restaurant.ID)
           .ThenBy(restaurant => restaurant.Complaint.Name)
           .ToList();

Since this returns a different list, I would advice using a different variable to avoid mutating state.