How do I determine a mapped drive's actual path?

Question

I expanded on ibram's answer and created this class (which has been updated per comment feedback). I've probably over documented it, but it should be self-explanatory.

/// <summary>
/// A static class to help with resolving a mapped drive path to a UNC network path.
/// If a local drive path or a UNC network path are passed in, they will just be returned.
/// </summary>
/// <example>
/// using System;
/// using System.IO;
/// using System.Management;    // Reference System.Management.dll
/// 
/// // Example/Test paths, these will need to be adjusted to match your environment. 
/// string[] paths = new string[] {
///     @"Z:\ShareName\Sub-Folder",
///     @"\\ACME-FILE\ShareName\Sub-Folder",
///     @"\\ACME.COM\ShareName\Sub-Folder", // DFS
///     @"C:\Temp",
///     @"\\localhost\c$\temp",
///     @"\\workstation\Temp",
///     @"Z:", // Mapped drive pointing to \\workstation\Temp
///     @"C:\",
///     @"Temp",
///     @".\Temp",
///     @"..\Temp",
///     "",
///     "    ",
///     null
/// };
/// 
/// foreach (var curPath in paths) {
///     try {
///         Console.WriteLine(string.Format("{0} = {1}",
///             curPath,
///             MappedDriveResolver.ResolveToUNC(curPath))
///         );
///     }
///     catch (Exception ex) {
///         Console.WriteLine(string.Format("{0} = {1}",
///             curPath,
///             ex.Message)
///         );
///     }
/// }
/// </example>
public static class MappedDriveResolver
{
    /// <summary>
    /// Resolves the given path to a full UNC path if the path is a mapped drive.
    /// Otherwise, just returns the given path.
    /// </summary>
    /// <param name="path">The path to resolve.</param>
    /// <returns></returns>
    public static string ResolveToUNC(string path) {
        if (String.IsNullOrWhiteSpace(path)) {
            throw new ArgumentNullException("The path argument was null or whitespace.");
        }

        if (!Path.IsPathRooted(path)) {
            throw new ArgumentException(
                string.Format("The path '{0}' was not a rooted path and ResolveToUNC does not support relative paths.",
                    path)
            );
        }

        // Is the path already in the UNC format?
        if (path.StartsWith(@"\\")) {
            return path;
        }

        string rootPath = ResolveToRootUNC(path);

        if (path.StartsWith(rootPath)) {
            return path; // Local drive, no resolving occurred
        }
        else {
            return path.Replace(GetDriveLetter(path), rootPath);
        }
    }

    /// <summary>
    /// Resolves the given path to a root UNC path if the path is a mapped drive.
    /// Otherwise, just returns the given path.
    /// </summary>
    /// <param name="path">The path to resolve.</param>
    /// <returns></returns>
    public static string ResolveToRootUNC(string path) {
        if (String.IsNullOrWhiteSpace(path)) {
            throw new ArgumentNullException("The path argument was null or whitespace.");
        }

        if (!Path.IsPathRooted(path)) {
            throw new ArgumentException(
                string.Format("The path '{0}' was not a rooted path and ResolveToRootUNC does not support relative paths.",
                path)
            );
        }

        if (path.StartsWith(@"\\")) {
            return Directory.GetDirectoryRoot(path);
        }

        // Get just the drive letter for WMI call
        string driveletter = GetDriveLetter(path);

        // Query WMI if the drive letter is a network drive, and if so the UNC path for it
        using (ManagementObject mo = new ManagementObject()) {
            mo.Path = new ManagementPath(string.Format("Win32_LogicalDisk='{0}'", driveletter));

            DriveType driveType = (DriveType)((uint)mo["DriveType"]);
            string networkRoot = Convert.ToString(mo["ProviderName"]);

            if (driveType == DriveType.Network) {
                return networkRoot;
            }
            else {
                return driveletter + Path.DirectorySeparatorChar;
            }
        }           
    }

    /// <summary>
    /// Checks if the given path is a network drive.
    /// </summary>
    /// <param name="path">The path to check.</param>
    /// <returns></returns>
    public static bool isNetworkDrive(string path) {
        if (String.IsNullOrWhiteSpace(path)) {
            throw new ArgumentNullException("The path argument was null or whitespace.");
        }

        if (!Path.IsPathRooted(path)) {
            throw new ArgumentException(
                string.Format("The path '{0}' was not a rooted path and ResolveToRootUNC does not support relative paths.",
                path)
            );
        }

        if (path.StartsWith(@"\\")) {
            return true;
        }

        // Get just the drive letter for WMI call
        string driveletter = GetDriveLetter(path);

        // Query WMI if the drive letter is a network drive
        using (ManagementObject mo = new ManagementObject()) {
            mo.Path = new ManagementPath(string.Format("Win32_LogicalDisk='{0}'", driveletter));
            DriveType driveType = (DriveType)((uint)mo["DriveType"]);
            return driveType == DriveType.Network;
        }
    }

    /// <summary>
    /// Given a path will extract just the drive letter with volume separator.
    /// </summary>
    /// <param name="path"></param>
    /// <returns>C:</returns>
    public static string GetDriveLetter(string path) {
        if (String.IsNullOrWhiteSpace(path)) {
            throw new ArgumentNullException("The path argument was null or whitespace.");
        }

        if (!Path.IsPathRooted(path)) {
            throw new ArgumentException(
                string.Format("The path '{0}' was not a rooted path and GetDriveLetter does not support relative paths.",
                path)
            );
        }

        if (path.StartsWith(@"\\")) {
            throw new ArgumentException("A UNC path was passed to GetDriveLetter");
        }

        return Directory.GetDirectoryRoot(path).Replace(Path.DirectorySeparatorChar.ToString(), "");
    }
}

I can't remember where I found this, but it works without p/invoke. It's what rerun posted before.

you need to reference System.Management.dll:

using System.IO;
using System.Management;

code:

public void FindUNCPaths()
{
   DriveInfo[] dis = DriveInfo.GetDrives();
   foreach( DriveInfo di in dis )
   {
      if(di.DriveType == DriveType.Network)
      {
         DirectoryInfo dir = di.RootDirectory;
         // "x:"
         MessageBox.Show( GetUNCPath( dir.FullName.Substring( 0, 2 ) ) );
      }
   }
}

public string GetUNCPath(string path)
{
   if(path.StartsWith(@"\\")) 
   {
      return path;
   }

   ManagementObject mo = new ManagementObject();
   mo.Path = new ManagementPath( String.Format( "Win32_LogicalDisk='{0}'", path ) );

   // DriveType 4 = Network Drive
   if(Convert.ToUInt32(mo["DriveType"]) == 4 )
   {
      return Convert.ToString(mo["ProviderName"]);
   }
   else 
   {
      return path;
   }
}

Update: Explicitly running as administrator will not show mapped drives. Here is an explanation of this behaviour: https://stackoverflow.com/a/11268410/448100 (in short: administrator has a different user context, so no access to mapped drives of normal user)

Here are some code samples:

• Using P/Invoke

All of the magic derives from a Windows function:

    [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);

Example invocation:

var sb = new StringBuilder(512);
var size = sb.Capacity;
var error = Mpr.WNetGetConnection("Z:", sb, ref size);
if (error != 0)
    throw new Win32Exception(error, "WNetGetConnection failed");
 var networkpath = sb.ToString();

I've written a method for this. It returns a UNC path if it is a mapped drive, otherwise it returns the path unchanged.

public static string UNCPath(string path)
{
    using (RegistryKey key = Registry.CurrentUser.OpenSubKey("Network\\" + path[0]))
    {
        if (key != null)
        {
            path = key.GetValue("RemotePath").ToString() + path.Remove(0, 2).ToString();
        }
    }
    return path;
}

EDIT

You now can use the Method even with already UNC paths. The above version of the method throws an exception if given a UNC path.

public static string UNCPath(string path)
{
    if (!path.StartsWith(@"\\"))
    {
        using (RegistryKey key = Registry.CurrentUser.OpenSubKey("Network\\" + path[0]))
        {
            if (key != null)
            {
                return key.GetValue("RemotePath").ToString() + path.Remove(0, 2).ToString();
            }
        }
    }
    return path;
}

I think you can use the "Network" key From the "Current User" Hive, In the Registry. The Mapped Drives Are Listed There With Their Shared Path On Server.

If there is no mapped drive in the system, so there is no "Network" Key In The "Current User" Hive.

Now, I'm using this way, no external dll nor anything else.

I could not replicate ibram's or Vermis' answer due to the problem I mentioned in a comment under Vermis' answer, about a type initializer exception.

Instead, I discovered I could query for all the drives currently on the computer and then loop through them, like so:

using System.IO; //For DirectoryNotFound exception.
using System.Management;


/// <summary>
/// Given a local mapped drive letter, determine if it is a network drive. If so, return the server share.
/// </summary>
/// <param name="mappedDrive"></param>
/// <returns>The server path that the drive maps to ~ "////XXXXXX//ZZZZ"</returns>
private string CheckUNCPath(string mappedDrive)
{
    //Query to return all the local computer's drives.
    //See http://msdn.microsoft.com/en-us/library/ms186146.aspx, or search "WMI Queries"
    SelectQuery selectWMIQuery = new SelectQuery("Win32_LogicalDisk");
    ManagementObjectSearcher driveSearcher = new ManagementObjectSearcher(selectWMIQuery);

    //Soem variables to be used inside and out of the foreach.
    ManagementPath path = null;
    ManagementObject networkDrive = null;
    bool found = false;
    string serverName = null;

    //Check each disk, determine if it is a network drive, and then return the real server path.
    foreach (ManagementObject disk in driveSearcher.Get())
    {
        path = disk.Path;

        if (path.ToString().Contains(mappedDrive))
        {
            networkDrive = new ManagementObject(path);

            if (Convert.ToUInt32(networkDrive["DriveType"]) == 4)
            {
                serverName = Convert.ToString(networkDrive["ProviderName"]);
                found = true;
                break;
            }
            else
            {
                throw new DirectoryNotFoundException("The drive " + mappedDrive + " was found, but is not a network drive. Were your network drives mapped correctly?");
            }
        }
    }

    if (!found)
    {
        throw new DirectoryNotFoundException("The drive " + mappedDrive + " was not found. Were your network drives mapped correctly?");
    }
    else
    {
        return serverName;
    }
}

This works for x64 Windows 7, for .NET 4. It should be usable in case you're getting that exception that was mentioned above.

I did this using the stuff given from MSDN and bits from ibram's or Vermis' answers, though it was a bit difficult to find specific examples on the MSDN. Resources used:

MSDN : Win32_LogicalDisk Class

MSDN : System.Management namespace

MSDN : WMI Queries example:

using System;
using System.Management;
class Query_SelectQuery
{
    public static int Main(string[] args) 
    {
        SelectQuery selectQuery = new 
            SelectQuery("Win32_LogicalDisk");
        ManagementObjectSearcher searcher =
            new ManagementObjectSearcher(selectQuery);

        foreach (ManagementObject disk in searcher.Get()) 
        {
            Console.WriteLine(disk.ToString());
        }

        Console.ReadLine();
        return 0;
    }
}

QueryDosDevice translates a drive letter into the path that it expands to.

Note that this will translate ALL drive letters, not just those that are mapped to network connections. You need to already know which are network paths, or to parse the output to see which are network.

Here's the VB signature

Declare Function QueryDosDevice Lib "kernel32" Alias "QueryDosDeviceA" (
       ByVal lpDeviceName    As String, 
       ByVal lpTargetPath As String, 
       ByVal ucchMax As Integer) As Integer 

And the C# one

[DllImport("kernel32.dll")]
static extern uint QueryDosDevice(string lpDeviceName, IntPtr lpTargetPath, uint ucchMax);