I have a third party DLL to integrate with their application. It is a 32 bit C++ DLL that does not expose itself via COM, and I have not been supplied source code or a header file.
It was supplied with working VB.NET example code in a WinForms example. This works, as long as the executable is run from the same directory as the API DLL and the application for which the API is interfacing.
I was using the example function declaration:
Declare Ansi Function GetVersion Lib "ThirdPartyAPI.dll" () As Integer
However, we’ll be using the API calls from a C# library to be used in a web site or web service, so I converted the example VB code to
[DllImport("ThirdPartyAPI.dll", SetLastError = true, CharSet = CharSet.Ansi)]
public static extern int GetVersion();
If I call this from within the C# library I get the error
Unhandled Exception: System.DllNotFoundException: Unable to load DLL
'ThirdPartyAPI.dll': A dynamic link library (DLL) initialization
routine failed. (Exception from HRESULT: 0x8007045A)
I took an alternative route and put the original working VB code from the example into its own VB.NET DLL and called that via C#. I got the same error. Strangely, a call to the VB.NET DLL from a VB.NET console app works.
In summary:
A simple VB.NET console app will work
A simple VB.NET WinForms app will work
A simple VB.NET console app can call GetVersion via a VB.NET DLL
A simple C# console app cannot call GetVersion via a VB.NET DLL
A simple C# console app cannot call GetVersion directly.
This could be to do with incorrectly defining the function calls. At
this stage, I’m not too worried about this.
32 bit compilation does not fix the issue
I have tried this on Server 2008 R2 and Windows 7 Enterprise
I created a WCF host via an NT service to expose the functions, hoping this would work around file locations and dependencies. This was written in VB.NET and placed in the same folder as ThirdPartyApi.dll.
None of the code in the NT service could access GetVersion
None of the code in the WCF service could access GetVersion
Please note, in all of the above cases, the executables are in the same directory as ThirdPartyApi.dll. All of its dependencies also exist in this directory.
Can anyone explain this behaviour, or suggest how this can be made to work within a C# web site?
Thanks
The error code is 0x8007045A. That is a COM error code that maps to the Win32 error code ERROR_DLL_INIT_FAILED. Which is described as:
A dynamic link library (DLL) initialization routine failed.
What this means is that your DLL was found, in spite of the perhaps misleading exception class DllNotFoundException. However, the DLL failed to load. You can gain no more information from the system. There is no mechanism for the DLL to report reasons why it failed to load. I suggest that you contact the vendor of the DLL and ask for support.
Related
I have an electron app which needs to call some methods from an existing DLL. The DLL is a C# DLL and I tried using electron-edge-js but got some errors like : The edge module has not been pre-compiled for Electron version
Can you please let me know how can I call C# DLL methods from electron? Also if you can point me to a sample code for the same.
Thanks in advance.
I will give you a brief description of my software before I ask questions.
So there is a front end C# code which provides the user interface and a back end C++ code that deals with the hardware.
The C# project creates an executable (.exe) file and the C++ project creates a DLL which talk with each other using pinvoke calls (import/export functions). All this worked fine on WEC7.
Now, we are moving to WEC2013 with Toradex. I downloaded the WEC2013 SDK from Toradex’s website and was able to port my code and build it on VS2013.
I copied all the required files on a USB and when I tried running it the C# exe is not able to communicate with the C++ Dll. The error I get is :
missingmethodexception can't find pinvoke dll “xyz.dll”
I have made sure the dll exists at the specified location. The dll also has the required export functions.
First I thought the function parameters in the export functions could be an issue, but I tried calling function which requires no parameter with the same result.
Any help will be really appreciated.
I'm trying to call a C++ DLL from ASP.NET 4.0 web application but keep getting a DLL Import error - unable to load library 'Library name'.
I've read a lot of blogs where developers experience the same probem and what seems to be working for most people is adding the path to where the unmanaged DLLs are to the PATH Environment Variable
I've done the same on the server and double, tripple checked that I spalled the path correctly and that the C++ DLLs are in that folder but when I view the application in the browser I'm still getting the same error.I've placed logging in the code and it's definitely coming from the portion of code which calls the unmanaged DLL.
Here is some information on my environment:
Windows Server 2003
IIS 6.0
.NET Framework 4.0
ASP.NET MVC 4.0
C#
On the dev machine it works if I copy the unmamanaged DLLs to C:\Program Files\IIS Express
Tried copying the C++ DLLs to the bin folder but as far as I understand ASP.NET copies the DLLs from the bin folder in inetpub\wwwroot\sitename\bin to a dynamic location when it executes the code but this process excludes the unmanaged DLLs.Any advice on what else I can try?
EDIT:
In terms of the code it's exactly the same as any other interop code,I have a wrapper class where I use DllImport to define all th required function calls and in my code I create a new instance of the wrapper and call the required function.As I mentioned this works fine on the dev machine as long as the C++ DLLs are i the IISExpress folder but when I deploy to the server it throws the above mentioned error:
[DllImport("My3rdparty.dll", CallingConvention = CallingConvention.Cdecl)]
private static extern int myfunction(int handle, int* response, int timer);
So after weeks of struggling I came up with a work around.The integration that I was implementing was for credit card processing. Along with the C++ DLLs they also have a compiled configuration file called system.dna and my suspicion is that when you add the folder containing the interop DLLs to the PATH Environment Variables it does not pick up the system.dna file.
As a workaround I created a WCF service which is installed as a Windows Service on the server and I've placed the logic for doing payments into this service and the web application simply talks to the service.I hope this helps other developers who are facing the same issue
My intention is, to run a Web service which accesses C++ native functions. Therefore I created a WCF Service Application (which contains contract and implementation) which references a C++/ CLI Wrapper around my Native C++ code. I did the following steps (following 2b from http://blogs.msdn.com/b/jorman/archive/2007/08/31/loading-c-assemblies-in-asp-net.aspx)
The native C++ API is exported.
native C++ dll's are loaded with "delayed loaded"
I set a path for native dll and its 3rd party dll's in the Web.config
defined asp-compatibility in the web.config file
Defined a Global.asax File for accessing the loading path for native dll's
I can run the service as long as I don't create the wrapper-object, which creates the native C++ object in the constructor.The problem is the creation of the native C++ object. If I test it with the WCFTestClient I get the unspecific errors:
Failed to invoke the service. Possible causes: The service is offline or inaccessible.
My question is: Is something wrong in this concept? I can use this wrapper and the native C++ object if I call it from a C#-Project. Do I have to choose another project type than a WCF Service Application?
Thank you for your help!
The concept is right, and it should work fine. I think when the service try to create the native C++ object, an error/exception happens, and which crashes the service. I suggest you write a small C# test program, which calls the C++/CLI DLL to create the native C++, if this small programs works fine, then move the code to your service.
Or you can debug the service, find the actual error, that would help too.
Alright, so maybe this is inadvisable, but I'm writing a Web Service for an existing application. I'm trying to use the C# Library we wrote for the project, and that C# Library uses functions from a dll that is not acreated from a .NET project. I know the DLL isn't a problem, because the actual application (A windows form application) that uses the c# Library has no problem performing operations that use this dll, but my web service always crashes when the dll methods are called. The exception is:
"Unable to load DLL 'foo.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)"} System.Exception {System.DllNotFoundException}
A sample of the import from the c# Library:
[DllImport("foo.dll")]
protected static extern void DllFunction(string param1, int param2, int param3);
I tried adding foo.dll to the Bin directory of my project, but this didn't work. I feel like I must be missing something really obvious. Any suggestions? I've read some funky things about DLLs and web services and tried a couple of fixes such as http://sites.google.com/site/tosapage/programming/asp-net#dll but they didn't work.
I would run the winforms exe with depends.exe. You might be getting that error for a dell that the dll you are calling needs.