Mapped Drive to UNC

[Hoobs]

Using .NET 4

I'm trying to convert from Mapped Drive paths (e.g. "Z:\tmp\test.txt => \\server\tmp\test.txt") and I'm having mixed results.

I used a function from http://www.wiredprairie.us/blog/index.php/archives/22 that uses WNetGetConnection(http://msdn.microsoft.com/en-us/libr...=vs.85%29.aspx), which makes this arguably also a c++ question, and it worked the first time, but in subsequent uses it is returning error code 2250, which is ERROR_NO_NETWORK. I am very much still connected to the drive, and it worked minutes earlier, but no more.

Anyone have a better way or know what might be the issue?

Thanks!

Code for reference:

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

public static string DriveMapPathToUNC(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;
        }