How to use custom sorting, based on the "Sort()" method of List<OwnObject>

In a previous post, I wanted to custom order a list of strings (List<string>). This is working fine now.

Now I would like a step further and sort a list of objects, having the mentioned strings as their name.

I thought this might be easy:

public class OwnObject : IComparable
    public int CompareTo(object obj)
    {
        if (!(obj is OwnObject)) return 0;

        string s1 = this.Name;
        string s2 = (obj as OwnObject).Name;
        ...
    }
    ...
}

… and in another file, do something like:

...ToList().Sort(OwnObject.CompareTo);

However, it’s not that simple: I get the following compiler message:

Argument 1: cannot convert from 'method group' to 'System.Collections.Generic.IComparer<OwnObject>'.

I thought I was doing something similar like the CompareDinosByLength from the Microsoft learning website.

What am I doing wrong here?

>Solution :

If your OwnObject already implements IComparable (or IComparable<OwnObject>, then simply call the parameterless List<T>.Sort() method.

If you pass a method to Sort like in your example, then it must be compatible with the Comparison<T> delegate, which expects two strongly typed parameters. You can use it when T is not comparable or the default comparison is not preferable:

// Custom sorting by name if OwnObject does NOT have a proper IComparable implementation
ownObjectsList.Sort((x, y) => x.Name.CompareTo(y.Name));

Remark from the question author:

ToList().Sort() makes no sense: it should be:

resulting_list = ....ToList();
resulting_list.Sort();