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;
        }

[dglienna]

NET USE /? will give you the parameters that you'd normally use.

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation. All rights reserved.

C:\Users\David>net use
New connections will be remembered.

There are no entries in the list.

C:\Users\David>

[Hoobs]

Thanks for the reply, David.

NET USE tells me :
Status Local Remote Network

--------------------------------------------------------------------------
OK N: \\server1\ Microsoft Windows Network

Which tells me the connection should be okay.

As a little more information, this program is a service that will be open user-specified text files, and they might specify Mapped, UNC or local and I need to be able to handle all three. Since C# doesn't like Mapped paths, I'm resorting to this.

When I call WNetGetConnection on "N:" it returns 2250, even though net use still shows okay.




EDIT:

I tried making a basic C console program and it worked great, so I'm guessing it lies somewhere in the character encoding.

[Hoobs]

New Resolution:
Since it was running in a service, the user running the program was Local System, not the logged in user, so the mapped drives were different. Running the service as myself made the C++ function below work 100% of the time. The C# version in OP was still hit-and-miss.



Old Resolution:
I resolved it, though not how I had hoped. Instead of trying to invoke through C Sharp, I just made a CLR DLL that had the C++ managed code, and imported that. For those who come after me, here's the C function that worked well:

static System::String^ MappedPathToUNC(System::String^ path)
		{
			DWORD MAX_DEVICE_LENGTH = 1000;
			TCHAR* szDeviceName = new TCHAR[MAX_DEVICE_LENGTH];
			memset(szDeviceName, '\0', MAX_DEVICE_LENGTH); 
			DWORD dwResult, cchBuff = sizeof(MAX_DEVICE_LENGTH); 


			char* charpath = (char*)(void*)System::Runtime::InteropServices::Marshal::StringToHGlobalAnsi(path->Substring(0,2));
			wchar_t* tpath = new wchar_t[MAX_DEVICE_LENGTH];

			memset(tpath, '\0', MAX_DEVICE_LENGTH);

			DWORD dwNum = MultiByteToWideChar (CP_ACP, 0, charpath, -1, NULL, 0);
			MultiByteToWideChar (CP_ACP, 0, charpath, -1, tpath, dwNum );


			dwResult = WNetGetConnection(
				tpath,
				szDeviceName, &MAX_DEVICE_LENGTH); 

			System::String ^ str = gcnew System::String(szDeviceName);

			str += path->Substring(2, path->Length-2);

			return str;
		}

Note: This function assumes the first two characters are a letter and a colon, like Z: or N:.