How to check whether 2 DirectoryInfo objects are pointing to the same directory?

Question

I have 2 DirectoryInfo objects and want to check if they are pointing to the same directory. Besides comparing their Fullname, are there any other better ways

Answer 1

Case-insensitive comparison is the best you can get. Extract it to a helper class just in case mankind comes up with a better method.

public static class DirectoryInfoExtensions
{
    public static bool IsEqualTo(this DirectoryInfo left, DirectoryInfo right)
    {
        return left.FullName.ToUpperInvariant() == right.FullName.ToUpperInvariant();
    }
}

and use:

if (di1.IsEqualTo(di2))
{
    // Code here
}

Answer 2

Some extension methods that I wrote for a recent project includes one that will do it:

    public static bool IsSame(this DirectoryInfo that, DirectoryInfo other)
    {
        // zip extension wouldn't work here because it truncates the longer 
        // enumerable, resulting in false positive

        var e1 = that.EnumeratePathDirectories().GetEnumerator();
        var e2 = other.EnumeratePathDirectories().GetEnumerator();

        while (true)
        {
            var m1 = e1.MoveNext();
            var m2 = e2.MoveNext();
            if (m1 != m2) return false; // not same length
            if (!m1) return true; // finished enumerating with no differences found

            if (!e1.Current.Name.Trim().Equals(e2.Current.Name.Trim(), StringComparison.InvariantCultureIgnoreCase))
                return false; // current folder in paths differ
        }
    }

    public static IEnumerable<DirectoryInfo> EnumeratePathDirectories(this DirectoryInfo di)
    {
        var stack = new Stack<DirectoryInfo>();

        DirectoryInfo current = di;

        while (current != null)
        {
            stack.Push(current);
            current = current.Parent;
        }

        return stack;
    }

    // irrelevant for this question, but still useful:

    public static bool IsSame(this FileInfo that, FileInfo other)
    {
        return that.Name.Trim().Equals(other.Name.Trim(), StringComparison.InvariantCultureIgnoreCase) &&
               that.Directory.IsSame(other.Directory);
    }

    public static IEnumerable<DirectoryInfo> EnumeratePathDirectories(this FileInfo fi)
    {
        return fi.Directory.EnumeratePathDirectories();
    }

    public static bool StartsWith(this FileInfo fi, DirectoryInfo directory)
    {
        return fi.Directory.StartsWith(directory);
    }

    public static bool StartsWith(this DirectoryInfo di, DirectoryInfo directory)
    {
        return di.EnumeratePathDirectories().Any(d => d.IsSame(directory));
    }

Answer 3

Inspired from here:

static public bool SameDirectory(string path1, string path2)
{
    return (
        0 == String.Compare(
            System.IO.Path.GetFullPath(path1).TrimEnd('\\'),
            System.IO.Path.GetFullPath(path2).TrimEnd('\\'),
            StringComparison.InvariantCultureIgnoreCase))
        ;
}    

Works for file too...

(BTW theoretically questions are duplicate, but this is the original and the other one is the most answered one...)

HTH

Answer 4

Under Linux you could compare the INode numbers of the two files wheather they are identical. But under Windows there is no such concept, at least not that I know off. You would need to use p/invoke to resolve the links if any.

Comparing strings is the best you can do. Note that using String.Compare(str1, str2, StringComparison.InvariantCultureIgnoreCase) is a bit faster than you approach.

Answer 5

You can use Uri objects instead. However, your Uri objects must point to a "file" inside these directories. That file doesn't actually have to exist.

    private void CompareStrings()
    {
        string path1 = @"c:\test\rootpath";
        string path2 = @"C:\TEST\..\TEST\ROOTPATH";
        string path3 = @"C:\TeSt\RoOtPaTh\";

        string file1 = Path.Combine(path1, "log.txt");
        string file2 = Path.Combine(path2, "log.txt");
        string file3 = Path.Combine(path3, "log.txt");

        Uri u1 = new Uri(file1);
        Uri u2 = new Uri(file2);
        Uri u3 = new Uri(file3);

        Trace.WriteLine(string.Format("u1 == u2 ? {0}", u1 == u2));
        Trace.WriteLine(string.Format("u2 == u3 ? {0}", u2 == u3));

    }

This will print out:

u1 == u2 ? True
u2 == u3 ? True