Ordering a System.Collections.IList

Question

Is it possible to order a System.Collection.IList without casting it to a known type?

I'm receiving a list as object and casting it to a IList using

var listType = typeof(List<>);
var cListType = listType.MakeGenericType(source.GetType());
var p = (IList)Activator.CreateInstance(cListType);
var s = (IList)source;

and I want to order it based on Id which may or may not be available.

What I want to procude is something like:

if (s.First().GetType().GetProperties().where(m=>m.Name.Contians("Id")).FirstOrDefault != null)
{
     s=s.OrderBy(m=>m.Id);
}

However, s does not have the extension method "Order" and neither have the extension method "First"

How do you want to order things if you don't even know what you order??? — bash.d, Apr 17 '13 at 10:00
no its not possible withoud generics or without writing your own extension methos afaik. but what you could do, is casting it to object that would work with your reflection solution. — stylefish, Apr 17 '13 at 10:01
Possible duplicate http://stackoverflow.com/questions/15486/sorting-an-ilist-in-c-sharp — Yahya, Apr 17 '13 at 10:02
What exactly do you want to order these unknown objects by if you don't know what they are? — thecoop, Apr 17 '13 at 10:02

score 1 · Accepted Answer · answered Apr 17 '13 at 10:06

Try next code. It will not sort if there is no id property on your source type

void Main()
{
    var source = typeof(Student);

    var listType = typeof(List<>);
    var cListType = listType.MakeGenericType(source);
    var list = (IList)Activator.CreateInstance(cListType);

    var idProperty = source.GetProperty("id");

    //add data for demo
    list.Add(new Student{id = 666});
    list.Add(new Student{id = 1});
    list.Add(new Student{id = 1000});

    //sort if id is found
    if(idProperty != null)
    {
        list = list.Cast<object>()
                   .OrderBy(item => idProperty.GetValue(item))
                   .ToList();
    }

    //printing to show that list is sorted
    list.Cast<Student>()
        .ToList()
        .ForEach(s => Console.WriteLine(s.id));
}

class Student
{
    public int id { get; set; }
}

prints:

1
666
1000

Ordering a System.Collections.IList

1 Answers1