sort files of folder in ascending order in C#

Question

I want to sort the files of folder in the ascending order so that I can combine that files properly but the output I am getting is, 1,10,11 like wise and I want the output as, 1,2,3.. like wise. I am using this,

                DirectoryInfo di = new DirectoryInfo(source_path);
                FileInfo[] arrFi = di.GetFiles("*.*");
                //arrFi.OrderBy(fi=>fi.LastWriteTime);
                Array.Sort(arrFi.OrderBy(fi => fi.LastWriteTime));

Answer 1

It's unclear what is the desired result looks like. If you want to sort files by their last write time a simple Linq query will do:

  var arrFi = new DirectoryInfo(source_path)
    .EnumerateFiles("*.*")
    .OrderBy(file => file.LastWriteTime)
    .ToArray();

If you want to order files by their names in natural order (ie "1" < "5" < "9" < "10" < "12" < "100" ) the query itself will be as easy as the previous one:

  var arrFi = new DirectoryInfo(source_path)
    .EnumerateFiles("*.*")
    .OrderBy(file => file.Name, new StringNaturalComparer(null))
    .ToArray();

But you have to implement the comparer :

  public sealed class StringNaturalComparer : IComparer<String> {
    private readonly IComparer<string> m_Comparer;

    private static List<string> ToChunks(string value) {
      List<string> result = new();

      StringBuilder sb = null;

      bool isDigit = false;

      foreach (var c in value) {
        if (sb is null) {
          sb = new StringBuilder(value.Length);
          isDigit = char.IsDigit(c);
          sb.Append(c);
        }
        else if (isDigit != char.IsDigit(c)) {
          result.Add(sb.ToString());
          sb.Clear();
          isDigit = char.IsDigit(c);
        }

        sb.Append(c);
      }

      if (sb != null)
        result.Add(sb.ToString());

      return result;
    }

    public StringNaturalComparer(IComparer<string> comparer) {
      m_Comparer = comparer == null ? StringComparer.Ordinal : comparer;
    }

    public int Compare(string left, string right) {
      if (ReferenceEquals(left, right))
        return 0;
      else if (left == null)
        return -1;
      else if (right == null)
        return 1;

      var lefts = ToChunks(left);
      var rights = ToChunks(right);

      int result;

      for (int i = 0; i < Math.Min(lefts.Count, rights.Count); ++i) {
        string leftChunk = lefts[i];
        string rightChunk = rights[i];

        if (char.IsDigit(leftChunk[0]) && char.IsDigit(rightChunk[0])) {
          result = leftChunk.Length.CompareTo(rightChunk.Length);

          if (result != 0)
            return result;
        }

        result = m_Comparer.Compare(leftChunk, rightChunk);

        if (result != 0)
          return result;
      }

      return lefts.Count.CompareTo(rights.Count);
    }
  }