how to extract common file path from list of file paths in c#

Question

What is the best way extract the common file path from the list of file path strings in c#?

Eg: I have a list 5 file paths in List variable, like below

c:\

Answer 1

Because everything is best solved with LINQ*:
^{*not everything is best solved with LINQ.}

using System.Collections.Generic;
using System.IO;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        List<string> Files = new List<string>()
        {
            @"c:\abc\pqr\tmp\sample\b.txt",
            @"c:\abc\pqr\tmp\new2\c1.txt",
            @"c:\abc\pqr\tmp\b2.txt",
            @"c:\abc\pqr\tmp\b3.txt",
            @"c:\a.txt"
        };

        var MatchingChars =
            from len in Enumerable.Range(0, Files.Min(s => s.Length)).Reverse()
            let possibleMatch = Files.First().Substring(0, len)
            where Files.All(f => f.StartsWith(possibleMatch))
            select possibleMatch;

        var LongestDir = Path.GetDirectoryName(MatchingChars.First());
    }
}

---

Explanation:

The first line gets a list of lengths of possible matches to evaluate. We want the longest possibility first (so i reverse the enumeration which would be 0, 1, 2, 3; turning it into 3, 2, 1, 0).

I then get the string to match, which is simply a substring of the first entry of the given length.

I then filter the results, to ensure we only include possible matches that all files start with.

Finally, i return the first result, which will be the longest substring and call path.getdirectoryname to ensure if something has a few identical letters in the filenames it isn't included.

Answer 2

Keep a tally of each segment and keep going while all the paths start with the tally.

void Main()
{
    string[] paths = new[] { @"c:\abc\pqr\tmp\sample\b.txt",
                            @"c:\abc\pqr\tmp\new2\c1.txt",
                            @"c:\abc\pqr\tmp\b2.txt",
                            @"c:\abc\pqr\tmp\b3.txt",
                            @"c:\abc\pqr\tmp\tmp2\b2.txt"};

    var test = new List<string>();
    var common = paths[0].Split('\\').TakeWhile ( segment => 
    {
        test.Add ( segment );
        return paths.All ( path => path.StartsWith ( String.Join ("\\", test )  + "\\") ) ;
    } );

    Console.WriteLine ( String.Join ("\\", common ) );
}

Answer 3

The selected solution does not work properly if one of the paths is exactly the directory name that should be returned. I think there should be:

from len in Enumerable.Range(0, matchingNames.Min(s => s.Length) + 1).Reverse()