Generic Sorting on List<T>

c#, extension-methods, generics

Solution

You just need to define a second generic type, so you can pass in a `List<T>` and a separate comparison (which I called U):

public static class ObjectExtension 
{ 
    public static List<T> Sort<T,U>(this List<T> o, Func<T, U> keySort, ESortDirection direction) where U : IComparable 
    { 
        if (direction == ESortDirection.asc) 
        { 
            o.Sort((a, b) => keySort(a).CompareTo(keySort(b))); 
        } 
        else 
        { 
            o.Sort((a, b) => keySort(b).CompareTo(keySort(a))); 
        } 
        return o; 
    } 
}

That being said, I question the usefulness of this. Why not just use the standard LINQ OrderBy?

OrderBy is slightly different, since this would do sorting in place, and OrderBy returns a new sorted `IEnumerable<T>`, but sticking to standards is typically more maintainable.

Problem

I have the following code: ``` public class OMyObject { public int Id { get; set; } public string Value { get; set; } public DateTime? MyDate { get; set; } } ``` I also have this code: ``` public static class ObjectExtension { public static List<OMyObject> Sort<T>(this List<OMyObject> o, Func<OMyObject, T> keySort, ESortDirection direction) where T : IComparable { if (direction == ESortDirection.asc) { o.Sort((a, b) => keySort(a).CompareTo(keySort(b))); } else { o.Sort((a, b) => keySort(b).CompareTo(keySort(a))); } return o; } } ``` Now I have a test console app which does the following: ``` var myObjectList = new List<OMyObject> { new OMyObject {Id = 4, MyDate = DateTime.Now.AddDays(4), Value = "Test 4"}, new OMyObject {Id = 2, MyDate = DateTime.Now.AddDays(2), Value = "Test 2"}, new OMyObject {Id = 1, MyDate = DateTime.Now.AddDays(1), Value = "Test 1"}, new OMyObject {Id = 3, MyDate = DateTime.Now.AddDays(3), Value = "Test 3"}, }; Console.WriteLine("Sort By Nullable Date ASC"); myObjectList.Sort(id => (DateTime)id.MyDate, ESortDirection.asc); foreach (var item in myObjectList) { Console.WriteLine(item.Id + " - " + item.MyDate + " - " + item.Value); } Console.WriteLine("Sort By ID DESC"); myObjectList.Sort(id => id.Id, ESortDirection.desc); foreach (var item in myObjectList) { Console.WriteLine(item.Id + " - " + item.MyDate + " - " + item.Value); } Console.ReadLine(); ``` So you can see that I am passing in a property to sort on. The question is this: How can I make my Sort() extension method generic to be able to pass in any List object to sort? So if I created a OMySecondObject, I want to use the same method for sorting. I tried replacing `List<OMyObject>` with `List<T>` or `List<object>` but that does not work. Any thoughts? Let me know if you need further clarification with what I am attempting to do. Thanks UPDATE: SOLUTION Okay based on my discussion and answers provided (thank you very much to everyone who responded) I have figured out an easier way to do this. I have this method which simulates a database call: ``` public static IEnumerable<OMyObject> GetObject() { var myObjectList = new List<OMyObject> { new OMyObject {Id = 4, MyDate = DateTime.Now.AddDays(4), Value = "Test 4"}, new OMyObject {Id = 2, MyDate = DateTime.Now.AddDays(2), Value = "Test 2"}, new OMyObject {Id = 1, MyDate = DateTime.Now.AddDays(1), Value = "Test 1"}, new OMyObject {Id = 3, MyDate = DateTime.Now.AddDays(3), Value = "Test 3"}, }; return myObjectList; } ``` I then just sort this list as follows: ``` IEnumerable<OMyObject> myObjectList = GetObject(); myObjectList = myObjectList.OrderBy(id => id.MyDate); ``` Again, thank you everyone for helping me figure this out and showing me the better way of handling this. THANKS!!

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