[RESOLVED] Get UNC from network mapped drive letter

[Fedaykin]

Does anyone have a handy way to get the full UNC (\\servername\) from a network mapped drive (X:\)?

Every method that I've tried on here and other sites seems to be deprecated.

[.paul.]

Have a look at this...

https://codejournalweb.wordpress.com...network-drive/

[Fedaykin]

Paul,

No joy. I modified the code in my class to:

Public Declare Function WNetGetConnection Lib "mpr.dll" Alias _
             "WNetGetConnectionA" (ByVal lpszLocalName As String,
             ByVal lpszRemoteName As String, ByRef cbRemoteName As Integer) As Integer
 
    Public Shared Function GetUNCPath(ConnStr As String)
 
        Dim ret As Integer
        Dim out As String = New String(" ", 260)
        Dim len As Integer = 260
 
        ret = WNetGetConnection(ConnStr, out, len)
        If out.Count > 0 Then
            Return out.Trim
            Console.WriteLine("UNC Path:   " & out.Trim)
        Else
            Return String.Empty
            Console.WriteLine("Drive not found")
        End If
        ' Console.WriteLine(out)
        Console.ReadLine()
    End Function

I'm calling the Function:

Dim TxtPath As String = Me.TextBox1.Text 'This is L:\Project\Xray
            Dim DirPath As String = GetUNCPath(TxtPath)

The function is returning String.Empty

[.paul.]

Try it with TxtPath being just L:/

[2kaud]

TxtPath needs to be just L: - as you specify the local device name, not a path.

[Fedaykin]

Still not getting anything but String.Empty. I modified the function to resolve the URL down to L:\ like this:

Public Declare Function WNetGetConnection Lib "mpr.dll" Alias _
             "WNetGetConnectionA" (ByVal lpszLocalName As String,
             ByVal lpszRemoteName As String, ByRef cbRemoteName As Integer) As Integer
 
    Public Shared Function GetUNCPath(ConnStr As String)
 
        'ConnStr comes in as L:\Project\Xray
        Dim letterOnly As String = ConnStr.Substring(0, 3) 'Resolves to L:\
        Dim ret As Integer
        Dim out As String = New String(" ", 260) 'Not sure what the purpose of this is?
        Dim len As Integer = 260
 
        ret = WNetGetConnection(letterOnly, out, len)
        If out.Count > 0 Then
            Dim UNCPrefix As String = out.Trim         'This is resulting in an empty string??
            Dim UNCPath As String = ConnStr.Substring(3)
            Dim fullPath As String = UNCPrefix & UNCPath
            Return fullPath
            Console.WriteLine("UNC Path:   " & out.Trim)
        Else
            Return String.Empty
            Console.WriteLine("Drive not found")
        End If
        ' Console.WriteLine(out)
        Console.ReadLine()
    End Function

Dim TxtPath As String = Me.TextBox1.Text 'This is L:\Project\Xray
            Dim DirPath As String = GetUNCPath(TxtPath)

[Fedaykin]

Deleted post, it was repeated for some reason.

[2kaud]

See my post #5! - Just needs to be L:

[.paul.]

Dim letterOnly As String = ConnStr.Substring(0, 2) 'Resolves to L:

[Fedaykin]

TxtPath needs to be just L: - as you specify the local device name, not a path.

Changing from L:\ to L: still produces a blank string returned:

Public Declare Function WNetGetConnection Lib "mpr.dll" Alias _
             "WNetGetConnectionA" (ByVal lpszLocalName As String,
             ByVal lpszRemoteName As String, ByRef cbRemoteName As Integer) As Integer
 
    Public Shared Function GetUNCPath(ConnStr As String)
       
        'ConnStr comes in as L:\Project\Xray
 
        Dim letterOnly As String = ConnStr.Substring(0, 2) 'Resolves to L: (Neither L: or L:\ works)
        Dim ret As Integer
        Dim out As String = New String(" ", 260)
        Dim len As Integer = 260
 
        ret = WNetGetConnection(letterOnly, out, len)
        If out.Count > 0 Then
            Dim UNCPrefix As String = out.Trim                  'This is resulting in an empty string?
            Dim UNCPath As String = ConnStr.Substring(3)
            Dim fullPath As String = UNCPrefix & UNCPath
            Return fullPath
            Console.WriteLine("UNC Path:   " & out.Trim)
        Else
            Return String.Empty
            Console.WriteLine("Drive not found")
        End If
        ' Console.WriteLine(out)
        Console.ReadLine()
    End Function

[2kaud]

I'm not a VB programmer, so can't give you vb code. But this c++ code produces the expected output on my computer

#include <winnetwk.h>
#pragma comment(lib, "mpr")

int main()
{
	char szDeviceName[260];
	DWORD cchBuff = sizeof(szDeviceName);

	switch (WNetGetConnection("z:", szDeviceName, &cchBuff))
	{
		//
		// Print the connection name or process errors.
		//
		case NO_ERROR:
			printf("Connection name: %s\n", szDeviceName);
			break;

			//
			// The device is not a redirected device.
			//
		case ERROR_NOT_CONNECTED:
			printf("Device z: not connected.\n");
			break;

			//
			// The device is not currently connected, but it is a persistent connection.
			//
		case ERROR_CONNECTION_UNAVAIL:
			printf("Connection unavailable.\n");
			break;

			//
			// Handle the error.
			//
		default:
			printf("WNetGetConnection failed.\n");
	}
}

In your VB code, you're not checking the return value for error - so don't know what error is occurring. If you obtain and show the return value of WNetGetConnection() then it might indicate the reason for the problem.

PS The network drive is not already connected then WNetGetConnection() may fail. In this case you need to first connect to the network drive.

[techgnome]

Have you tried setting some break points, and stepping through the code to see what is what? If it's returning an empty string, then it seems like it is failing the if out.count check... so that' where I'd start...
I don't think .Count does what you think it does... in fact, I'm not even sure why you're using it at all. If you're looking to see if the UNC resolved or not, look at ret ... that should return a value that indicates if it was resolved successfully or not.

-tg

[.paul.]

There's also a possibility the the API might need you to target x86

[Fedaykin]

Have you tried setting some break points, and stepping through the code to see what is what? If it's returning an empty string, then it seems like it is failing the if out.count check... so that' where I'd start...
I don't think .Count does what you think it does... in fact, I'm not even sure why you're using it at all. If you're looking to see if the UNC resolved or not, look at ret ... that should return a value that indicates if it was resolved successfully or not.

-tg

I agree, none of this does what I think it should do! I was just using the example code that was referenced by .paul in his original reply. I've tried many of these examples all over the internet, none of them work as intended. II am not married to this method, I'm just searching for ANY method to return the UNC of a mapped drive letter on the users machine. I've set break points on everything.

Ret returns code 2250 'The network connecton could not be found' according to: https://docs.microsoft.com/en-us/win...nt-error-codes

[techgnome]

OK, now here's the next thing. Windows made a change at some point, I think it was with Win7, in how and when it does the mapping. It used to be that when you logged into Windows, i would re-connect all mapped drives instantly... or attempt to... but that would cause problems if the resource was off line, or required the user to connect via VPN or something else first. This slowed down the login process for a lot of users. Even when the resource is available, it slows down because it's having to send the login info, and reconnect the drive. They were also finding out that often, just because a drive was mapped, doesn't mean a user was actually going to use it. At my last job, I had some dozen mapped drives, I almost never used them. So what MS did was to delay when the connection happens. It got delayed until the drive was actually requested... then the login info was sent and the connection was made. And that maybe what's happening in this case. The drive isn't actually available because it hasn't been connected to and established yet. Just a guess though...

-tg

[2kaud]

Return code 2250 is ERROR_NOT_CONNECTED. ie the network connection does not exist.

//
// MessageId: ERROR_NOT_CONNECTED
//
// MessageText:
//
// This network connection does not exist.
//
#define ERROR_NOT_CONNECTED              2250L

Before using WNetGetConnection(), you first need to connect to the device.

Also from MSDN https://docs.microsoft.com/en-us/win...getconnectiona

If the network connection was made using the Microsoft LAN Manager network, and the calling application is running in a different logon session than the application that made the connection, a call to the WNetGetConnection function for the associated local device will fail. The function fails with ERROR_NOT_CONNECTED or ERROR_CONNECTION_UNAVAIL. This is because a connection made using Microsoft LAN Manager is visible only to applications running in the same logon session as the application that made the connection. (To prevent the call to WNetGetConnection from failing it is not sufficient for the application to be running in the user account that created the connection.)

[Fedaykin]

I think you're both on to something with the connection not existing. I found this https://social.msdn.microsoft.com/Fo...orum=vbgeneral But of course there is no example of the method I need which I think would be WNetGetUniversalName. Unfortunately I do not understand this InAttribute stuff.

[Fedaykin]

Well, okay. How so how do I 'wake up' the connection? Doing this on the L: drive returns FALSE:

Dim letterOnly As String = ConnStr.Substring(0, 2)
        Dim driveExists As Boolean = Directory.Exists(letterOnly & ":") 'Tried both L: and L:\, both show FALSE even though my local machine is mapped to the L drive!

[2kaud]

An alternative is to execute the cmd "net use L:" (or whatever drive letter is required), send its output to a file and then read and parse the file. This doesn't require the connection to be established as long as it is defined. Sorry, but I can't give you the VB code (as I only use c/c++), but the c++ code is:

int main()
{
	system("net use z: > netusez.txt 2> null:");

	if (auto f = fopen("netusez.txt", "r"); f != NULL) {
		char ln[256];

		fgets(ln, 255, f);
		fgets(ln, 255, f);
		if (strncmp(ln, "Remote name", 11) == 0)
			if (auto r = strchr(ln, '\\'); r != NULL)
				cout << r << endl;
			else
				cout << "Not a valid remote name\n";
		else
			cout << "Not a valid drive\n";
	} else
		cout << "Problem opening file\n";
}

This should be fairly easy to translate into VB by someone who knows VB.

[techgnome]

Well, okay. How so how do I 'wake up' the connection? Doing this on the L: drive returns FALSE:

Dim letterOnly As String = ConnStr.Substring(0, 2)
        Dim driveExists As Boolean = Directory.Exists(letterOnly & ":") 'Tried both L: and L:\, both show FALSE even though my local machine is mapped to the L drive!

Haven't tried it, but from what I remember you have to use it... not just check to see if it exists, but use it... like get the directory listing or something. And it doesn't always wake up on the first attempt either, that it might take 2-3 attempts.

-tg

[ChrisE]

try a loop, see if it returns

Imports System.Text


Public Class Form2

    Public Declare Function WNetGetConnection Lib "mpr.dll" Alias _
             "WNetGetConnectionA" (ByVal lpszLocalName As String, _
             ByVal lpszRemoteName As StringBuilder, ByRef cbRemoteName As Integer) As Integer

   


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        For Each drv In IO.DriveInfo.GetDrives()
            If drv.DriveType = IO.DriveType.Network Then
                Dim UncPath As New System.Text.StringBuilder(255)
                WNetGetConnection(drv.Name.Replace("\", ""), UncPath, UncPath.Capacity)
                MessageBox.Show(drv.Name & " maps to " & UncPath.ToString)
            End If
        Next
    End Sub
End Class

see this thread http://www.vbforums.com/showthread.p...-network-drive Post#5

[Fedaykin]

Any looping or multiple attempts to wake the connection returned false. It's pretty silly to me that .NET does not have a good method to resolve a mapped drive letter to a proper UNC.

I thank everyone for their input! I was inspired by 2kaud's C++ method, but I opt'd for a simpler call to command prompt NET USE.

I modified a function that I found on the web for my purpose that works pretty well. It dumps the entire cmd prompt text into a string (no need to write out and read from .txt file!), then I just parse out the Remote Name using Regex:

Public Shared Function GetUNCPath(ConnStr As String)
        Dim UNCPath As String = Nothing
        Dim letterDrive As String = ConnStr.Substring(0, 2) 'Returns  'L:'
        If letterDrive <> "\" Then
            Dim nakedPath As String = ConnStr.Substring(2) 'Returns  '\Folder\folder\file.txt'
            Dim si As ProcessStartInfo = New ProcessStartInfo("cmd.exe")
            si.RedirectStandardInput = True
            si.RedirectStandardOutput = True
            si.UseShellExecute = False
            Dim p As Process = Process.Start(si)
            p.StandardInput.WriteLine("NET USE " & letterDrive)
            p.StandardInput.WriteLine("exit")
            Dim output As String = p.StandardOutput.ReadToEnd()
            Dim UNCPrefix As String = Regex.Match(output, "(?<=Remote name\s{7}).*?(?=\n)").ToString 'Regex grabs string between 'Remote name(+7 spaces)' and a new line in the string.
            Dim RemLineBrk As String = UNCPrefix.Replace(vbCr, "") 'Removes the line break at the end of the string
            UNCPath = RemLineBrk & nakedPath
        ElseIf letterDrive = "\" Then
            UNCPath = ConnStr
        End If
        Return UNCPath
    End Function

Edit: Added code to handle if the directory path was unmapped (already a full UNC)

Then call it:

Dim MappedPath As String = Me.TextBox1.Text
Dim UNCPath As String = GetUNCPath(MappedPath )

[2kaud]

I realise this thread is resolved, but after some investigation and for info, there is an easier method of obtaining the UNC from a network mapped drive letter.

The mapped drive letters are stored as keys (without the : ) under:

HKEY_CURRENT_USER/Network

Each mapped drive letter is then a separate key under this (without the : ). The value of RemotePath gives the UNC of the network mapped drive letter.

This method is obviously easier (and quicker!) than executing NET USE and parsing the output someway.

[Fedaykin]

I realise this thread is resolved, but after some investigation and for info, there is an easier method of obtaining the UNC from a network mapped drive letter.

The mapped drive letters are stored as keys (without the : ) under:

HKEY_CURRENT_USER/Network

Each mapped drive letter is then a separate key under this (without the : ). The value of RemotePath gives the UNC of the network mapped drive letter.

This method is obviously easier (and quicker!) than executing NET USE and parsing the output someway.

Wow, nice! What's your VB.net code for reading the registry key?

[2kaud]

Wow, nice! What's your VB.net code for reading the registry key?

Sorry, but I don't use VB, only c/c++. Perhaps some VB guru could provide this?

[ChrisE]

Wow, nice! What's your VB.net code for reading the registry key?

turn on google ....https://www.dotnetheaven.com/article...stry-in-vb.net