Linq ordering by number on file name

Question

I'm trying to order a set of files base on its file name. Input is a directory with files like:

f0.vesperdp
f1.vesperdp
f2.vesperdp
....
f9.vesperdp
f10.vesperdp
f11.vesperdp
f12.vesperdp

I've built this LINQ query to sort them:

if (Directory.Exists(path))
{
    var directoryInfo = new DirectoryInfo(path);
    var files = from file in directoryInfo.EnumerateFiles()

    .Where(f => f.Extension == PAGE_FILE_EXTENSION)
                orderby file.Name.Substring(1, file.Name.Length - 1) ascending
                select file.FullName;

    return files.ToArray<string>();
}

But they are returning like

f0.vesperdp
f1.vesperdp
f10.vesperdp
....
f19.vesperdp
f2.vesperdp
f20.vesperdp
f21.vesperdp

I need them to be sorted using natural order (from 0 to n as f0,f1,f2...,f9,f10,f11) how can fix my orderby filter to match this? Or if there's other way, how can I achieve that? Thanks in advance.

http://www.codinghorror.com/blog/2007/12/sorting-for-humans-natural-sort-order.html — Kendall Frey, Jul 23 '12 at 17:10
See this [custom sort](http://stackoverflow.com/a/11052176/932418) — L.B, Jul 23 '12 at 17:10

naspinski · Answer 1 · 2012-07-23T17:14:31.427

It is ordering the string correctly, you are going to have to pull just the number out, convert to Integer, then order. This is untested, but you get the idea:

public int GetInt(string filename)
{
    int idx = file.Name.IndexOf(".");
    if(idx < 0) throw new InvalidOperationException();
    return Convert.ToInt32(filename.SubString(1, file.Name.Length - (idx - 1)));
}

Then your orderby part:

.Where(f => f.Extension == PAGE_FILE_EXTENSION)
    orderby GetInt(file.Name) ascending
    select file.FullName;

score 1 · Accepted Answer · answered Jul 23 '12 at 17:11

Naspinski's correct in theory, but here's the solution in code.

if (Directory.Exists(path))
{
    var directoryInfo = new DirectoryInfo(path);
    var files = from file in directoryInfo.EnumerateFiles()

    .Where(f => f.Extension == PAGE_FILE_EXTENSION)
                orderby int.Parse(file.Name.Substring(1, file.Name.IndexOf('.')-1)) ascending
                select file.FullName;

    return files.ToArray<string>();
}

The order-by clause basically changes to pull everything between the leading 'f' and the first dot, which from your examples will be a number string, which is then parsed into an integer number and displayed.

NominSim · Answer 3 · 2012-07-23T17:20:02.663

0

Just pull the int value out of the name and orderby using that value:

.Where(f => f.Extension == PAGE_FILE_EXTENSION)
        orderby int.Parse(file.Name.Substring(1, file.Name.Length -
                          file.Extension.Length-1)) ascending
        select file.FullName;

edited Jul 23 '12 at 17:20

answered Jul 23 '12 at 17:08

NominSim

8,447
3
28
38

This will throw an exception. You need to stop your parsing at the period. – jsmith Jul 23 '12 at 17:14
Won't work; file.Name includes the extension, so the substring being pulled from `f0.vesperdp` would be `0.vesperdp` which is non-numeric. – KeithS Jul 23 '12 at 17:15

Linq ordering by number on file name

3 Answers3