Sort by number order in a foreach loop

Question

I'm making a program which gets me a list, but the list is not in order. I need to list to be in order like...

1.txt
2.txt
3.txt

However, it's coming out like

2.txt
1.txt
3.txt

All in random order. I am using

foreach (var file in d.GetFiles("*.txt"))
{                 
    tosend = tosend + file.Name + "\n";
}

I don't want a single string. After it gets the file name it's going to readtext of other files its set and add it. So like [1.txt] Text

From the [documentation](https://msdn.microsoft.com/en-us/library/8he88b63(v=vs.110).aspx): *"The order of the returned file names is not guaranteed; use the `Sort` method if a specific sort order is required"* — UnholySheep, Apr 20 '17 at 19:42
And what if the files are `10.txt`, `9.txt` and `1.txt`. What order would you like them in now? — Eric Lippert, Apr 20 '17 at 19:44
http://stackoverflow.com/questions/248603/natural-sort-order-in-c-sharp — Dmitry Bychenko, Apr 20 '17 at 19:49

score 4 · Answer 1 · edited Apr 10 '22 at 08:41

4

Use LINQ:

foreach (var file in d.GetFiles("*.txt").OrderBy(x => x.Name).ToList())
{
    ...
}

If the files will always be a number.txt you can use

foreach (var file in d.GetFiles("*.txt").OrderBy(x => int.Parse(x.Name.Substring(0,x.Name.IndexOf(".txt"))).ToList())
{
    ...
}

You will want to add some error checking.

edited Apr 10 '22 at 08:41

mkrieger1

19,194
5
54
65

answered Apr 20 '17 at 19:42

jkozlowski

178
10

3

What is the compelling benefit of the `ToList` ? – Eric Lippert Apr 20 '17 at 19:43
Doesnt quite work right https://gyazo.com/ef640852da17f25259a1440a960a976b – xxLoganxx Apr 20 '17 at 19:48
see the above edit for it not working the way you wanted – jkozlowski Apr 20 '17 at 19:54
You got your fix in a little faster than I could get it for you, I personally think mine is more readable, up to you. `d.GetFiles("*.txt").OrderBy(f => Int32.Parse(f.Name.Split('.').First())).ToList();` – Blake Thingstad Apr 20 '17 at 19:57
1

The ToList isn't necessary because the foreach loop will force the query to execute (which is why the ToList was probably there). If you remove the ToList you'll see it performs the same. – Blake Thingstad Apr 20 '17 at 20:09

score 1 · Answer 2 · answered Apr 20 '17 at 19:44

1

Or you can sort the array:

string[] files = d.GetFiles("*.txt")
Array.Sort(files, StringComparer.InvariantCulture);
foreach (var file in files)
{                 
   tosend = tosend + file.Name + "\n";
}

answered Apr 20 '17 at 19:44

NiVeR

9,644
4
30
35

Doesn't work file string[] files is not valid with system.io – xxLoganxx Apr 20 '17 at 19:48
Hmm..I don't have a way to try it right now, but according to the documentation (https://msdn.microsoft.com/en-us/library/07wt70x2(v=vs.110).aspx#Examples) it should work. – NiVeR Apr 20 '17 at 19:54

Igor · Answer 3 · 2017-04-20T19:45:17.663

0

Use Linq

// top of code file
using System.Linq;

In method:

var files = d.GetFiles("*.txt").OrderBy(file => file.Name).ToList();

or as a string as per your example

string tosend = string.Join("\n", d.GetFiles("*.txt")
         .Select(file => file.Name)
         .OrderBy(x => x));

This joins the returned ordered list of file names using \n as a separator.

edited Apr 20 '17 at 19:45

answered Apr 20 '17 at 19:41

Igor

60,821
10
100
175

1

I don't want to ToList though. Because there isnt going to be one thing after the tosend. It has to be other things so its all on one line. – xxLoganxx Apr 20 '17 at 19:43
It looks like OP wants a list in a text string not a `List` object. – MotKohn Apr 20 '17 at 19:45
@LoganRisen - I added a second example of how you can use linq. Here you get a single string of the file names joined (in order) by `"\n"`. – Igor Apr 20 '17 at 19:47
@LoganRisen - see Eric's comment though, sorting alphabetically does not work very well when you deal with numbers. – Igor Apr 20 '17 at 19:48

score 0 · Answer 4 · edited May 23 '17 at 11:54

0

If you are looking for Natural sort i.e.

  1.txt
  9.txt
 10.txt

you can use Interop as a quick (and may be a dirty) solution (see Natural Sort Order in C# for details)

using System.Runtime.InteropServices;

...

[DllImport("shlwapi.dll", CharSet = CharSet.Unicode)]
private static extern int StrCmpLogicalW(string left, string right);

...

// Obtain files
var files = d.GetFiles();

// Sort files in natural order
Array.Sort(files, (left, right) => StrCmpLogicalW(left.Name, right.Name));

// combine files' names into the string
string tosend = string.Join("\n", files);

edited May 23 '17 at 11:54

Community

1
1

answered Apr 20 '17 at 20:42

Dmitry Bychenko

180,369
20
160
215

@BJ Myers: `StrCmpLogicalW` is the function *File Explorer* uses to sort files, but you are quite right: *Interop* is often a dirty solution even if it's quick one. – Dmitry Bychenko Apr 20 '17 at 20:59

Sort by number order in a foreach loop

4 Answers4