Mapped network drives cannot be listed in C#

Question

I am trying to list all local drives in my application, and DriveInfo.GetDrives give back the local drive letters, and I need the mapped drives too.

Cur

Answer 1

OK, I found out how to get the disconnected drives on Vista. Not easy, but it is doable:

First, you'll need the pInvoke definition of the following WinAPI functions:

• WNetOpenEnum
• WNetEnumResource
• WNetCloseEnum

and those need a struct and some enums as well.

Then you need to call those multiple times, and at the end, you get the list. Here is the code, beware, it is long:

    [DllImport("MPR.dll", CharSet = CharSet.Auto)]
    static extern int WNetEnumResource(IntPtr hEnum, ref int lpcCount, IntPtr lpBuffer, ref int lpBufferSize);

    [DllImport("MPR.dll", CharSet = CharSet.Auto)]
    static extern int WNetOpenEnum(RESOURCE_SCOPE dwScope, RESOURCE_TYPE dwType, RESOURCE_USAGE dwUsage,
        [MarshalAs(UnmanagedType.AsAny)][In] object lpNetResource, out IntPtr lphEnum);

    [DllImport("MPR.dll", CharSet = CharSet.Auto)]
    static extern int WNetCloseEnum(IntPtr hEnum);

    public enum RESOURCE_SCOPE : uint
    {
        RESOURCE_CONNECTED = 0x00000001,
        RESOURCE_GLOBALNET = 0x00000002,
        RESOURCE_REMEMBERED = 0x00000003,
        RESOURCE_RECENT = 0x00000004,
        RESOURCE_CONTEXT = 0x00000005
    }
    public enum RESOURCE_TYPE : uint
    {
        RESOURCETYPE_ANY = 0x00000000,
        RESOURCETYPE_DISK = 0x00000001,
        RESOURCETYPE_PRINT = 0x00000002,
        RESOURCETYPE_RESERVED = 0x00000008,
    }
    public enum RESOURCE_USAGE : uint
    {
        RESOURCEUSAGE_CONNECTABLE = 0x00000001,
        RESOURCEUSAGE_CONTAINER = 0x00000002,
        RESOURCEUSAGE_NOLOCALDEVICE = 0x00000004,
        RESOURCEUSAGE_SIBLING = 0x00000008,
        RESOURCEUSAGE_ATTACHED = 0x00000010,
        RESOURCEUSAGE_ALL = (RESOURCEUSAGE_CONNECTABLE | RESOURCEUSAGE_CONTAINER | RESOURCEUSAGE_ATTACHED),
    }
    public enum RESOURCE_DISPLAYTYPE : uint
    {
        RESOURCEDISPLAYTYPE_GENERIC = 0x00000000,
        RESOURCEDISPLAYTYPE_DOMAIN = 0x00000001,
        RESOURCEDISPLAYTYPE_SERVER = 0x00000002,
        RESOURCEDISPLAYTYPE_SHARE = 0x00000003,
        RESOURCEDISPLAYTYPE_FILE = 0x00000004,
        RESOURCEDISPLAYTYPE_GROUP = 0x00000005,
        RESOURCEDISPLAYTYPE_NETWORK = 0x00000006,
        RESOURCEDISPLAYTYPE_ROOT = 0x00000007,
        RESOURCEDISPLAYTYPE_SHAREADMIN = 0x00000008,
        RESOURCEDISPLAYTYPE_DIRECTORY = 0x00000009,
        RESOURCEDISPLAYTYPE_TREE = 0x0000000A,
        RESOURCEDISPLAYTYPE_NDSCONTAINER = 0x0000000B
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct NetResource
    {
        public RESOURCE_SCOPE dwScope;
        public RESOURCE_TYPE dwType;
        public RESOURCE_DISPLAYTYPE dwDisplayType;
        public RESOURCE_USAGE dwUsage;
        [MarshalAs(System.Runtime.InteropServices.UnmanagedType.LPTStr)]
        public string lpLocalName;
        [MarshalAs(System.Runtime.InteropServices.UnmanagedType.LPTStr)]
        public string lpRemoteName;
        [MarshalAs(System.Runtime.InteropServices.UnmanagedType.LPTStr)]
        public string lpComment;
        [MarshalAs(System.Runtime.InteropServices.UnmanagedType.LPTStr)]
        public string lpProvider;
    }

    static System.Collections.Generic.Dictionary WNetResource(object resource)
    {
        System.Collections.Generic.Dictionary result = new System.Collections.Generic.Dictionary();

        int iRet;
        IntPtr ptrHandle = new IntPtr();
        try
        {
            iRet = WNetOpenEnum(
                RESOURCE_SCOPE.RESOURCE_REMEMBERED, RESOURCE_TYPE.RESOURCETYPE_DISK, RESOURCE_USAGE.RESOURCEUSAGE_ALL,
                resource, out ptrHandle);
            if (iRet != 0)
                return null;

            int entries = -1;
            int buffer = 16384;
            IntPtr ptrBuffer = Marshal.AllocHGlobal(buffer);
            NetResource nr;

            iRet = WNetEnumResource(ptrHandle, ref entries, ptrBuffer, ref buffer);
            while ((iRet == 0) || (entries > 0))
            {
                Int32 ptr = ptrBuffer.ToInt32();
                for (int i = 0; i < entries; i++)
                {
                    nr = (NetResource)Marshal.PtrToStructure(new IntPtr(ptr), typeof(NetResource));
                    if (RESOURCE_USAGE.RESOURCEUSAGE_CONTAINER == (nr.dwUsage
                        & RESOURCE_USAGE.RESOURCEUSAGE_CONTAINER))
                    {
                        //call recursively to get all entries in a container
                        WNetResource(nr);
                    }
                    ptr += Marshal.SizeOf(nr);
                    result.Add(nr.lpLocalName, nr);
                }

                entries = -1;
                buffer = 16384;
                iRet = WNetEnumResource(ptrHandle, ref entries, ptrBuffer, ref buffer);
            }

            Marshal.FreeHGlobal(ptrBuffer);
            iRet = WNetCloseEnum(ptrHandle);
        }
        catch (Exception)
        {
        }

        return result;
    }
    public static System.Collections.Generic.Dictionary WNetResource()
    {
        return WNetResource(null);
    }

You've got to call the WNetResource(), and you will get back the list of drives. (and cake :-))