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

Answer 1

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.

Answer 2

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";
}

Answer 3

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.

Answer 4

If you are looking for Natural sort ie

  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);