Help with LINQ distinct()

Question

I have a class called "Orders" that has the property of "City" among others. I am trying to write a LINQ statement that will get all the distinct cities from a list of orders and return them as a list of strings.

Here is what I have now.

public List<string> GetOrderCities(List<Order> orders)
{
   IEnumerable<string> cities= from o in orders
                                select o.City.Distinct().ToString();

   return cities.ToList();

}

However, when I run this by passing it a list of orders, I don't seem to be getting anything back. The list is empty that it is returning. The orders I am passing it do all have City values. Am I just flat out doing this wrong? Thanks!

Answer 1

You're miscalling the Distinct() method.

Change it to

return orders.Select(o => o.City).Distinct().ToList();

Or, using query comprehension syntax:

return (from o in orders
        select o.City
       ).Distinct().ToList();

(Note parentheses)

Your code calls Distinct on the City property itself, which is a string.
Since the String class implements IEnumerable<char>, this method returns an IEnumerable<char> containing all of the unique characters in the string.
You then call ToString() on this enumerable (which is a compiler-generated iterator type from System.Core.dll), which always returns System.Linq.Enumerable+d__81`1[System.Char].

Instead, you need to call .Distinct() on the IEnumerable<string> returned by the Select method.