How can I compare (directory) paths in C#?

Question

If I have two DirectoryInfo objects, how can I compare them for semantic equality? For example, the following paths should all be considered equal to C:\temp:

• C:\temp
• C:\temp\
• C:\temp\.
• C:\temp\x\..\..\temp\.

The following may or may not be equal to C:\temp:

• \temp if the current working directory is on drive C:\
• temp if the current working directory is C:\
• C:\temp.
• C:\temp...\

If it's important to consider the current working directory, I can figure that out myself, so that's not that important. Trailing dots are stripped in windows, so those paths really should be equal - but they aren't stripped in unix, so under mono I'd expect other results.

Case sensitivity is optional. The paths may or may not exist, and the user may or may not have permissions to the path - I'd prefer a fast robust method that doesn't require any I/O (so no permission checking), but if there's something built-in I'd be happy with anything "good enough" too...

Answer 1

bool equals = myDirectoryInfo1.FullName == myDirectoryInfo2.FullName;

?

Answer 2

 System.IO.Path.GetFullPath(pathA).Equals(System.IO.Path.GetFullPath(PathB));

Answer 3

It seems that P/Invoking GetFinalPathNameByHandle() would be the most reliable solution.

UPD: Oops, I didn't take into account your desire not to use any I/O

Answer 4

The "Name" properties are equal. Take:

DirectoryInfo dir1 = new DirectoryInfo("C:\\Scratch");
DirectoryInfo dir2 = new DirectoryInfo("C:\\Scratch\\");
DirectoryInfo dir3 = new DirectoryInfo("C:\\Scratch\\4760");
DirectoryInfo dir4 = new DirectoryInfo("C:\\Scratch\\4760\\..\\");

dir1.Name == dir2.Name and dir2.Name == dir4.Name ("Scratch" in this case. dir3 == "4760".) It's only the FullName properties that are different.

You might be able to do a recursive method to examine the Name properties of each parent given your two DirectoryInfo classes to ensure the complete path is the same.

EDIT: does this work for your situation? Create a Console Application and paste this over the entire Program.cs file. Provide two DirectoryInfo objects to the AreEquals() function and it will return True if they're the same directory. You might be able to tweak this AreEquals() method to be an extension method on DirectoryInfo if you like, so you could just do myDirectoryInfo.IsEquals(myOtherDirectoryInfo);

using System;
using System.Diagnostics;
using System.IO;
using System.Collections.Generic;

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(AreEqual(
                new DirectoryInfo("C:\\Scratch"),
                new DirectoryInfo("C:\\Scratch\\")));

            Console.WriteLine(AreEqual(
                new DirectoryInfo("C:\\Windows\\Microsoft.NET\\Framework"),
                new DirectoryInfo("C:\\Windows\\Microsoft.NET\\Framework\\v3.5\\1033\\..\\..")));

            Console.WriteLine(AreEqual(
                new DirectoryInfo("C:\\Scratch\\"),
                new DirectoryInfo("C:\\Scratch\\4760\\..\\..")));

            Console.WriteLine("Press ENTER to continue");
            Console.ReadLine();
        }

        private static bool AreEqual(DirectoryInfo dir1, DirectoryInfo dir2)
        {
            DirectoryInfo parent1 = dir1;
            DirectoryInfo parent2 = dir2;

            /* Build a list of parents */
            List<string> folder1Parents = new List<string>();
            List<string> folder2Parents = new List<string>();

            while (parent1 != null)
            {
                folder1Parents.Add(parent1.Name);
                parent1 = parent1.Parent;
            }

            while (parent2 != null)
            {
                folder2Parents.Add(parent2.Name);
                parent2 = parent2.Parent;
            }

            /* Now compare the lists */

            if (folder1Parents.Count != folder2Parents.Count)
            {
                // Cannot be the same - different number of parents
                return false;
            }

            bool equal = true;

            for (int i = 0; i < folder1Parents.Count && i < folder2Parents.Count; i++)
            {
                equal &= folder1Parents[i] == folder2Parents[i];
            }

            return equal;
        }
    }
}

Answer 5

There are some short comes to the implementation of paths in .NET. There are many complaints about it. Patrick Smacchia, the creator of NDepend, published an open source library that enables handling of common and complex path operations. If you do a lot of compare operations on paths in your application, this library might be useful to you.

Answer 6

GetFullPath seems to do the work, except for case difference (Path.GetFullPath("test")!=Path.GetFullPath("TEST")) and trailing slash. So, the following code should work fine:

String.Compare(
    Path.GetFullPath(path1).TrimEnd('\\'),
    Path.GetFullPath(path2).TrimEnd('\\'), 
    StringComparison.InvariantCultureIgnoreCase)

Or, if you want to start with DirectoryInfo:

String.Compare(
    dirinfo1.FullName.TrimEnd('\\'),
    dirinfo2.FullName.TrimEnd('\\'), 
    StringComparison.InvariantCultureIgnoreCase)