Can't find PInvoke DLL 'Mpr.dll'

Question

Hi All World Experts I am developing a .net 2.0 windows form application for a mobile device like scanner (Intermec CK3). The application is running fine on my windows XP. But when I moved the application to the scanner (Windows CE 6.1) and ran it. I got an error like Can't find PInvoke DLL Mpr.dll. I seached for the dll on the scanner and could find it. The dll is on the windows XP. Could you tell me what I have done wrong in my codes? Any help would be appreciated. [ private static extern ErrorCodes WNetAddConnection3( IntPtr hWndOwner NETRESOURCE lpNetResource string lpPassword string lpUserName int dwFlags); public enum ResourceScope { RESOURCE_CONNECTED = 1RESOURCE_GLOBALNETRESOURCE_REMEMBEREDRESOURCE_RECENTRESOURCE_CONTEXT}; public enum ResourceType {RESOURCETYPE_ANYRESOURCETYPE_DISKRESOURCETYPE_PRINTRESOURCETYPE_RESERVED}; public enum ResourceUsage { RESOURCEUSAGE_CONNECTABLE = 0x00000001RESOURCEUSAGE_CONTAINER = 0x00000002RESOURCEUSAGE_NOLOCALDEVICE = 0x00000004RESOURCEUSAGE_SIBLING = 0x00000008 RESOURCEUSAGE_ATTACHED = 0x00000010RESOURCEUSAGE_ALL = (RESOURCEUSAGE_CONNECTABLE | RESOURCEUSAGE_CONTAINER | RESOURCEUSAGE_ATTACHED) }; public enum ResourceDisplayType { RESOURCEDISPLAYTYPE_GENERICRESOURCEDISPLAYTYPE_DOMAINRESOURCEDISPLAYTYPE_SERVERRESOURCEDISPLAYTYPE_SHARERESOURCEDISPLAYTYPE_FILE RESOURCEDISPLAYTYPE_GROUPRESOURCEDISPLAYTYPE_NETWORKRESOURCEDISPLAYTYPE_ROOTRESOURCEDISPLAYTYPE_SHAREADMINRESOURCEDISPLAYTYPE_DIRECTORY RESOURCEDISPLAYTYPE_TREERESOURCEDISPLAYTYPE_NDSCONTAINER }; public enum ErrorCodes { NO_ERROR = 0 ERROR_NO_MORE_ITEMS = 259 ERROR_BAD_NETPATH = 53 ERROR_SESSION_CREDENTIAL_CONFLICT = 1219 }; ret = uint bufferSize = 16384; IntPtr buffer = Marshal .AllocHGlobal(( int )bufferSize); IntPtr handle = IntPtr .Zero; ErrorCodes result; ErrorCodes .ERROR_9999; NETRESOURCE nr = new NETRESOURCE (); nr.lpRemoteName = @ \myServer_Name ; nr.dwScope = ResourceScope .RESOURCE_GLOBALNET; nr.dwType = ResourceType .RESOURCETYPE_ANY; nr.dwDisplayType = ResourceDisplayType .RESOURCEDISPLAYTYPE_SHARE; nr.dwUsage = ResourceUsage .RESOURCEUSAGE_CONNECTABLE; result = WNetAddConnection3(handle nr my_password my_userID 1); DllImport ( Mpr.dll  EntryPoint = WNetAddConnection3  CallingConvention = CallingConvention .Winapi)]

Vulpes · Answer

One thing I notice straightaway is that you don't have the 'sequential layout' attribute specified on the NETRESOURCE class. So I'd see if it makes any difference if you add that: [StructLayout(LayoutKind.Sequential)] public class NETRESOURCE { public ResourceScope dwScope = 0; public ResourceType dwType = 0; public ResourceDisplayType dwDisplayType = 0; public ResourceUsage dwUsage = 0; public string lpLocalName = null; public string lpRemoteName = null; public string lpComment = null; public string lpProvider = null; } As the Compact Framework can only deal with unicode strings I'd also make that clear in the DllImport attribute for WNetAddConnection3: [DllImport(coredll.dll CharSet = CharSet.Unicode SetLastError = true)] static extern int WNetAddConnection3(IntPtr hWndOwner NETRESOURCE lpNetResource string lpPassword string lpUserName uint dwFlags); However after reading the article I linked to above I suspect there's an even worse problem namely that the strings within the NETRESOURCE class are not blittable! As that article was written for CF v1.0 I'm hoping that something might have been done about this in the meantime so I'd try the above changes first. However if it's no better then we'll have to use one of the approachs mentioned in the follow-up article ( http://msdn.microsoft.com/en-us/library/aa446529.aspx ) to try and deal with the string problem.

Lam Nguyen · Answer

Hi Vulpes I have added the definitions to the previous post and it's a complete codes... I really appreciate your precious times. Lam

Vulpes · Answer

According to the MSDN documentation (see the link in Sam's post above) the function is definitely supported by Windows CE so I'm puzzled that you're getting a NotSupported exception though there are a number of ways in which one can run aground when P/Invoking unmanaged functions using the Compact Framework (see http://msdn.microsoft.com/en-us/library/aa446536.aspx ). Are you absolutely sure that the error occurs on the line where you call WNetAddConnection3 and not somewhere else? If you are then can you post the definition you're using for the NETRESOURCE class - I assume it's a class rather than a struct as you're not passing it by reference.

Lam Nguyen · Answer

Hi Vulpes I changed my codes as below: namespace JDBarcodeReaderWinCE2 { public enum LocalMemoryFlags { LMEM_FIXED = 0x0000 LMEM_MOVEABLE = 0x0002 LMEM_NOCOMPACT = 0x0010 LMEM_NODISCARD = 0x0020 LMEM_ZEROINIT = 0x0040 LMEM_MODIFY = 0x0080 LMEM_DISCARDABLE = 0x0F00 LMEM_VALID_FLAGS = 0x0F72 LMEM_INVALID_HANDLE = 0x8000 LHND = (LMEM_MOVEABLE | LMEM_ZEROINIT) LPTR = (LMEM_FIXED | LMEM_ZEROINIT) NONZEROLHND = (LMEM_MOVEABLE) NONZEROLPTR = (LMEM_FIXED) } public enum ResourceScope { RESOURCE_CONNECTED = 1 RESOURCE_GLOBALNET RESOURCE_REMEMBERED RESOURCE_RECENT RESOURCE_CONTEXT } public enum ResourceType { RESOURCETYPE_ANY RESOURCETYPE_DISK RESOURCETYPE_PRINT RESOURCETYPE_RESERVED } public enum ResourceUsage { 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 ResourceDisplayType { RESOURCEDISPLAYTYPE_GENERIC RESOURCEDISPLAYTYPE_DOMAIN RESOURCEDISPLAYTYPE_SERVER RESOURCEDISPLAYTYPE_SHARE RESOURCEDISPLAYTYPE_FILE RESOURCEDISPLAYTYPE_GROUP RESOURCEDISPLAYTYPE_NETWORK RESOURCEDISPLAYTYPE_ROOT RESOURCEDISPLAYTYPE_SHAREADMIN RESOURCEDISPLAYTYPE_DIRECTORY RESOURCEDISPLAYTYPE_TREE RESOURCEDISPLAYTYPE_NDSCONTAINER } public class NETRESOURCE { public ResourceScope dwScope = 0; public ResourceType dwType = 0; public ResourceDisplayType dwDisplayType = 0; public ResourceUsage dwUsage = 0; public string lpLocalName = null; public string lpRemoteName = null; public string lpComment = null; public string lpProvider = null; } ... ... public class ServerUtility { const uint LMEM_ZEROINIT = 0x0040; [DllImport ( coredll.dll  SetLastError = true )] static extern int WNetAddConnection3( IntPtr hWndOwner NETRESOURCE lpNetResource string lpPassword string lpUserName uint dwFlags); [ DllImport ( coredll.dll )] static extern IntPtr LocalAlloc( uint uFlags UIntPtr uBytes); [DllImport ( coredll.dll  SetLastError = true )] static extern IntPtr LocalFree( IntPtr hMem); . . . int result uint bufferSize = 16384 IntPtr handle = IntPtr .Zero IntPtr buffer = LocalAlloc(LMEM_ZEROINIT new UIntPtr (bufferSize)); try { nr.lpRemoteName = @ \my_server_name nr.dwScope = ResourceScope .RESOURCE_GLOBALNET nr.dwType = ResourceType .RESOURCETYPE_ANY nr.dwDisplayType = ResourceDisplayType .RESOURCEDISPLAYTYPE_SHARE nr.dwUsage = ResourceUsage .RESOURCEUSAGE_CONNECTABLE result = WNetAddConnection3(handle nr my_password  my_user_id  1); LocalFree(buffer); } catch (Exception ex) { MessageBox.Show(catch it.... + msg); } } //ServerUtility } //namespace I ran the codes above and got the same error as before NotSupportException. I am not sure the coredll.lib supports WNetAddConnection3 function? Thank you Lam

Sam Hobbs · Answer

Vulpes knows much more about this than I do and I assume he already knows how to read the documentation. But just to clarify things WNetAddConnection3 says that it is in coredll.lib for CE and WNetAddConnection3 says it is in Mpr.lib for regular Windows.

Vulpes · Answer

To keep things simple just add these P/Invoke signatures to your class: [DllImport(coredll.dll)] static extern IntPtr LocalAlloc(uint uFlags UIntPtr uBytes); [DllImport(coredll.dll SetLastError=true)] static extern IntPtr LocalFree(IntPtr hMem); const uint LMEM_ZEROINIT = 0x0040; and then replace this line: IntPtr buffer = Marshal.AllocHGlobal((int)bufferSize); with this one: IntPtr buffer = LocalAlloc(LMEM_ZEROINIT new UIntPtr(bufferSize)); and replace this one (which I assume you have): Marshal.FreeHGlobal(buffer); with this: LocalFree(buffer);

Lam Nguyen · Answer

Hi Honestly I am lost. I am not sure where to start. I browsed the website http://pinvoke.net/default.aspx/kernel32/LocalAlloc.html and found a bunch of functions and do not know which one I should use. Cound you give me a start point on this new route? Thank you so much.

Vulpes · Answer

The not supported' exception may be coming from the call to Marshal.AllocHGlobal rather than WNetAddConnection3. It's a long time since I did anything with the compact framework but I have a vague recollection that Marshal.AllocHGlobal isn't supported and you have to use native memory management functions instead. Assuming I'm right about this then I'd try P/Invoking LocalAlloc ( http://pinvoke.net/default.aspx/kernel32/LocalAlloc.html ) and then LocalFree ( http://www.pinvoke.net/default.aspx/kernel32/LocalFree.html ) when you're done. Just change kernel32.dll to coredll.dll in the DllImport attributes.

Lam Nguyen · Answer

It looks like the coredll.dll exists some where in the scanner it is not visible like you said it's installed in the ROM. I changed the signature recompiled and ran the applicaltion it gave a different error. NotSupportedException. Thank you so much for your help.

Vulpes · Answer

'coredll.dll' is the main system dll for Windows CE but it'll probably be inside a ROM on the scanner so you won't be able to find it. However if you change your P/Invoke signature to the following then with luck it might work: [DllImport(coredll.dll)] static extern uint WNetAddConnection3(IntPtr hWndOwner ref NETRESOURCE lpNetResource string lpPassword string lpUserName uint dwFlags);

Lam Nguyen · Answer

The CoreDll.dll is not found on neither XP or Scanner. The Windows CE on the scanner is a custom built OP therefore I couldn't do any thing to it. How do you install a dll like coredll.dll in windows CE? I don't see regsvr32.exe nor cmd.exe programs on windows ce. Thank you in advance.

Vulpes · Answer

The function you're trying to call WNetAddConnection3 might actually be present in coredll.dll rather than mpr.dll on Windows CE 6.1. See its MSDN entry ( http://msdn.microsoft.com/en-us/library/ee493048(WinEmbedded.60).aspx ) which says it's in coredll.lib. I'd check that out before trying to copy mpr.dll across as the version in the latter may not work properly.

Lam Nguyen · Answer

Thank you for your response. I have made a typo on my post. The Mpr.dll is not found on the scanner but it is found on windows XP.

Vulpes · Answer

If 'Mpr.dll' is present on the scanner then the problem may be that another dll on which it depends is not present. You can check dependencies with the free tool Dependency Walker: http://www.dependencywalker.com/