how to sort strings with C#

Question

I have a class like

public class KeyNamePair
{
 public string Key {get;set;}

 public string Name{get;set;}
}

My code

List<KeyNamePair> list =new List<KeyNamePair>();

    list.Add("1", "Day 1");
    list.Add("2", "Day 11");
    list.Add("4", "Day 5");
    list.Add("6", "Day 13");

How can i sort the list to display

>  "Day1", "Day5", "Day 11", "Day 13"

in order?

i tried

var SortedList = source.OrderBy(x => x.Name).ToList();
            return SortedList;

this does not do any sort

Answer 1

Try something like:

var SortedList = source.OrderBy(x=>int.Parse(x.Name.Split(' ')[1])).ToList();
return SortedList;

It won't work if data is in other format, but it should work with format you provided. You cannot sort by string itself because string "13" < "5"

Answer 2

Does it sort like this by any chance?

Day 1 Day 11 Day 13 Day 5

This would be what I would expect. There is an overload on OrderBy to allow you to specify how to sort. The sort that is happening is an alphanumeric sort so it is doing it correct. If you did...

Day 01 Day 11 Day 13 Day 05

You would see it sorts correctly.

Answer 3

We can totally cheat here by PInvoking the Windows API function StrCmpLogicalW() which does a natural sort-order comparison between two strings.

Then we can just use the built-in List.Sort(). No need to involve Linq at all:

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;

namespace Demo
{
    class Program
    {
        [DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
        private static extern int StrCmpLogicalW(string lhs, string rhs);

        private void run()
        {
            var list = new List<KeyValuePair<string, string>>
            {
                new KeyValuePair<string, string>("1", "Day 1"), 
                new KeyValuePair<string, string>("2", "Day 11"), 
                new KeyValuePair<string, string>("4", "Day 5"),
                new KeyValuePair<string, string>("6", "Day 13")
            };

            list.Sort((lhs, rhs) => StrCmpLogicalW(lhs.Value, rhs.Value));

            foreach (var keyValuePair in list)
                Console.WriteLine(keyValuePair);
        }

        static void Main(string[] args)
        {
            new Program().run();
        }
    }
}

I'm assuming that you do indeed want to sort on "Value" and not on "Key" and that the problem you have is that the string numbers aren't sorting in numerical order.

---

EDIT: Applying Jim Tollan's idea, you could create an extension method to hide the PInvoke away like so:

public static class ListExt
{
    [DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
    private static extern int StrCmpLogicalW(string lhs, string rhs);

    // Version for lists of any type.
    public static void SortNatural<T>(this List<T> self, Func<T, string> stringSelector)
    {
        self.Sort((lhs, rhs) => StrCmpLogicalW(stringSelector(lhs), stringSelector(rhs)));
    }

    // Simpler version for List<string>
    public static void SortNatural(this List<string> self)
    {
        self.Sort(StrCmpLogicalW);
    }
}

Then the line that does the sorting of the list would look like this:

list.SortNatural(element => element.Value);

Answer 4

This should work:

list = list.OrderBy(kn => {
    var digits = kn.Name.Split().Last();
    int num = int.MaxValue;
    if (digits.All(Char.IsDigit))
    { 
        num = int.Parse(new string(digits.ToArray()));
    }
    return num;
}).ToList();

Side-Note: you could also use the already available KeyValuePair<string, string>.

Answer 5

I think that this is not a good approach but this work

list.OrderBy(x =>
     {
         return Int32.Parse(x.Name.Split(' ')[1]);
     });

Answer 6

you've got a few issues here:

1. you are trying to sort on the Name property which counts 'Day 1' and 'Day 11' as being more closely matched than 'Day 1' and 'Day 2'
2. You may be better sorting on the Key (also, I'd make the key numeric, rather than string if it will only ever contain numeric values).

Here's my revision:

public class KeyNamePair
{
    public int Key { get; set; }

    public string Name { get; set; }
}

List<KeyNamePair> list = new List<KeyNamePair>
    {
        new KeyNamePair() {Key = 1, Name = "Day 1"},
        new KeyNamePair() {Key = 4, Name = "Day 11"},
        new KeyNamePair() {Key = 2, Name = "Day 5"},
        new KeyNamePair() {Key = 6, Name = "Day 13"}
    };

var sortedList = list.Select(x => x).OrderBy(x => x.Key).ToList();

[edit] - I'm reflecting on the fact that I feel it would be better to refactor the logic of the class and the population of it, rather than try to co-erce some arbitary order that may fail on culture specific implementations, as strings are notoriously fragile in this respect.

Answer 7

I'm sure you will be happy with this:)

public class KeyNamePair : IComparable
{
  public string Key { get; set; }

  public string Name { get; set; }

  public KeyNamePair(string key, string name)
  {
    this.Key = key;
    this.Name = name;
  }

  public int CompareTo(object obj)
  {
    var tmp = (KeyNamePair)obj;
    var newKey = int.Parse(tmp.Name.Split(' ')[1]);

    var oldKey = int.Parse(Name.Split(' ')[1]);

    if (oldKey > newKey)
      return (1);
    if (oldKey < newKey)
      return (-1);
    else
      return (0);
  }
}

  List<KeyNamePair> list = new List<KeyNamePair>();

  list.Add(new KeyNamePair("1", "Day 1"));
  list.Add(new KeyNamePair("2", "Day 11"));
  list.Add(new KeyNamePair("4", "Day 5"));
  list.Add(new KeyNamePair("6", "Day 13"));
  list.Sort();

  foreach (var keyNamePair in list)
  {
    System.Console.Write(keyNamePair);
  }