Load files from a folder using natural order

Question

in a folder, I have these files. the order on windows explorer is:

input (1).jpg
input (2).jpg
input (101).jpg

This is the way I got the files from the folder:

var files = Directory.GetFiles(inputImage, "*.*", SearchOption.TopDirectoryOnly);

But the order will be:

input (1).jpg
input (101).jpg
input (2).jpg

Even I tried: Array.Sort(files);

But the order is the same, How can I load the files with this order:

input (1).jpg
input (2).jpg
input (101).jpg

Natural sorting http://www.codinghorror.com/blog/2007/12/sorting-for-humans-natural-sort-order.html — Mr47, Jun 18 '12 at 14:55

Jon Skeet · Answer 1 · 2012-06-18T15:06:45.657

You'll need to implement your own comparison to compare two strings in a way which "realizes" that they contain embedded non-zero-padded numbers. Explorer contains this logic already, and (as per the comment) this is exposed in StrCmpLogicalW which you could call with P/Invoke in a custom Comparer<string> implementation which you could pass to a sorting method.

If you know everything else about the name (i.e. the pattern) then it's easy to strip out the fixed parts for the comparison - but StrCmpLogicalW will give you a nice general implementation.

Of course if you're in control of whatever's creating the files, a simpler approach is to zero-pad the filenames to some reasonable number of digits, e.g. 5 or 6.

Not sure if its what explorer uses but Win32's StrCmpLogicalW would give the desired order — Alex K., Jun 18 '12 at 15:05

score 2 · Answer 2 · answered Jun 18 '12 at 15:00

2

Keep in mind that Array.Sort(files) is, by default, sorting file names as text, not as numbers. Try parsing the numbers and then sorting by those.

answered Jun 18 '12 at 15:00

Steve Konves

2,648
3
25
44

score 2 · Accepted Answer · answered Jun 18 '12 at 15:05

Well I'll try something like this:

        var files = from file in directoryInfo.EnumerateFiles()
        .Where(f => f.Extension == ".jpg")
                    orderby ExtractNumber(file.Name) ascending
                    select file.FullName;
        return files.ToList<string>();

Here we extract the file number -between the ( and )-.

private static object ExtractNumber(string p)
{
    int lenght = p.IndexOf(')') - p.IndexOf('(');
    return int.Parse(p.Substring(p.IndexOf('('), lenght - 1)); 
}

I'm pretty sure there must be an efficient way to do this, but just my two cents.

score 2 · Answer 4 · answered Jun 18 '12 at 15:41

If you load the files in a simple way:

string[] files = Directory.GetFiles ("folder");

and assuming that there is always a number in parentheses you can use a function:

Array.Sort (files, compareFilesWithBrackets);

with a comparison function:

public static int compareFilesWithBrackets (string arg1, string arg2)
{
        string filename1 = System.IO.Path.GetFileName (arg1); //extract filename from the path of the first file
        string filename2 = System.IO.Path.GetFileName (arg2); // extract second file filename
        Match m = Regex.Match (filename1, "\\(([0-9]+)\\)"); // check if there is (number) for file 1
        int file1 = 0; // if no number leave 0
        if (m.Success) { // else if success parse the number from brackets
            file1 = int.Parse (m.Groups [1].Value); 
        }
        m = Regex.Match (filename2, "\\(([0-9]+)\\)");
        int file2 = 0;
        if (m.Success) {
            file2 = int.Parse (m.Groups [1].Value); 
        }
        return file1 - file2;
}

score 1 · Answer 5 · answered Jun 18 '12 at 14:59

If it were me, I'd create a dictionary object and store the first value as the original filename, and the 2nd as a custom filename that you will need to massage.

So, for instance, the dictionary object would look something like this:

input (1).jpg    |  input (001).jpg
input (2).jpg    |  input (002).jpg
input (101).jpg  |  input (101).jpg

Then you can sort on the 2nd field, but pull the filename from the first field in the dictionary object.

score 1 · Answer 6 · answered Jun 18 '12 at 15:03

1

You can use the OrderBy extension, more details here http://msdn.microsoft.com/en-us/library/bb534966.aspx

It's a simple lambda expression the t=> t part. You can do some manipulation before it gets sorted if need be.

var files = Directory.GetFiles(inputImage, "*.*", SearchOption.TopDirectoryOnly).OrderBy(t => t);

If you wanted to sort only on the number, you could some some clever string substitution like

.OrderBy(t => t.Replace("input", "").Replace("(", "").Replace(")","").Trim());

answered Jun 18 '12 at 15:03

Breland

183
1
11

I tried this within Replace(".jpg", "") but it does not work :p – olidev Jun 18 '12 at 15:22
Ah, should have cast it to an int, eg .OrderBy(t => int.Parse(t.Replace("input", "").Replace("(", "").Replace(")","").Trim())); – Breland Jun 19 '12 at 13:13
Really, you could have just used a regular expression to grab the number, and ordered it on that. – Breland Jun 19 '12 at 13:15

score 1 · Answer 7 · edited May 23 '17 at 12:29

This CustomSort can help

List<string> list = new List<string>()
{
   "input (1).jpg","input (101).jpg", "input (11).jpg", "input (2).jpg"
};

var sortedList = list.CustomSort().ToList();

Output will be:

input (1).jpg
input (2).jpg
input (11).jpg
input (101).jpg

I'll copy the code here

public static class MyExtensions
{
    public static IEnumerable<string> CustomSort(this IEnumerable<string> list)
    {
        int maxLen = list.Select(s => s.Length).Max();

        return list.Select(s => new
        {
            OrgStr = s,
            SortStr = Regex.Replace(s, @"(\d+)|(\D+)", m => m.Value.PadLeft(maxLen, char.IsDigit(m.Value[0]) ? ' ' : '\xffff'))
        })
        .OrderBy(x => x.SortStr)
        .Select(x => x.OrgStr);
    }
}

Load files from a folder using natural order

7 Answers7