How to check if directory 1 is a subdirectory of dir2 and vice versa

Question

What is an easy way to check if directory 1 is a subdirectory of directory 2 and vice versa?

I checked the Path and DirectoryInfo helperclasses but found no system-r

Answer 1

The second directories(d2) full name will contain the full name of the first directory(d1) if it is a sub-folder of d1.

This assumes that you are using valid directories

if (d2.FullName.Contains(d1.FullName))
{
     //dowork
}

If you need to check for mapped drives you could try

    static void Main(string[] args)
    {
        if (GetUNCPath(d2.FullName).ToLower().Contains(GetUNCPath(d1.FullName).ToLower()))
        {
        }
    }

    [DllImport("mpr.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    private static extern int WNetGetConnection(
        [MarshalAs(UnmanagedType.LPTStr)] string localName,
        [MarshalAs(UnmanagedType.LPTStr)] StringBuilder remoteName, ref int length);

    private static string GetUNCPath(string originalPath)
    {

        StringBuilder sb = new StringBuilder(512);
        int size = sb.Capacity;
        // look for the {LETTER}: combination ...
        if (originalPath.Length > 2 && originalPath[1] == ':')
        {
            // don't use char.IsLetter here - as that can be misleading
            // the only valid drive letters are a-z && A-Z.
            char c = originalPath[0];
            if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'))
            {
                int error = WNetGetConnection(originalPath.Substring(0, 2), sb, ref size);
                if (error == 0)
                {
                    DirectoryInfo dir = new DirectoryInfo(originalPath);
                    string path = Path.GetFullPath(originalPath).Substring(Path.GetPathRoot(originalPath).Length);
                    return Path.Combine(sb.ToString().TrimEnd(), path);
                }
            }
        }
        return originalPath;
    }

Code for mapped drive taken from http://social.msdn.microsoft.com/Forums/en/csharpgeneral/thread/6f79f2b3-d092-431f-bc28-d15d93cf5d09