I have an ASP.NET WebApplication (.NET 4.0/C#) that works with an external COM dll (written in C++).
On a function call, which worked perfectly with an older ASP project, I get a AccessViolationException in the DLL code.
To debug it, I requested a debug version of the DLL from my colleague who wrote it. I have no access to the dll project or source code directly though.
How can I use this debug dll to find out where the error is occuring? I could not find a way to step into the method I am calling. Is it possible?
EDIT: I have the .pdb file as well, if that's any good. For some reason I cannot see the COM dll in the Debug->Windows->Modules overview. I'm really stuck, any help appreciated.
You need to have Unmanaged Code Debugging enabled.
From MSDN:
The Unmanaged code debugging property, available on the Debug page of the Project Designer, determines whether debugging of native code is supported. Select this option if you are making calls to COM objects, or if you start a custom program written in native code that calls your project and you need to debug the native code.
For ASP, you need to check 'Native Code' in the Debuggers section of the Web tab.
Also you should have Just My Code debugging disabled in the debugging options.
Perhaps you could use Ildasm.exe to rip through the dll to see what you are missing. As for violations it sounds as if it is similar to this issue. Try a static import from this SO. MsCorlib.dll may be having an issue with the third party dll.
Unmanaged DLL causing AccessViolationException
Be aware of the dependencies and that you may have some marshaling issues. I advise using DllImport in a console app to see if it can resolve. Best of lucK!
Related
When I enable unmanaged c++ debug with managed C# project in one solution in VS2010, usually, I get the messagebox popup 'HRESULT=0x8013134d. Errorcode=0x0'. I have no choice but to kill the process devenv.exe.
I searched some web pages all that showed the cause are interop cannot be supported (CORDBG_E_INTEROP_NOT_SUPPORTED). Is there any method could solve the problem?
Thanks a lot
I have a solution primarily based on C# projects, but I will occasionally need to use libraries written in native c++. The way I have solved this is by having a native project that simply acts as a wrapper for a native library, in this case OpenCV (I know I could use EMGUCV directly in C#, but in my experience it has some bugs that I would like to avoid and this is more a proof of concept anyways). I then have a C++ CLR project that references the native wrapper, and finally a C# project referencing the C++ CLR project. Strictly speaking I could just reference OpenCV directly from the CLR project instead of having the native wrapper project, but I would like to organize it this way both to conform to how the rest of the solution is organized and because I might at some point want to have this structure for another reason.
The first problem with this approach is that I can't find a way for Visual Studio to automatically include the dll of the native wrapper in the final target directory. Referencing the native project from the CLR project works flawlessly and referencing the CLR project from the C# project is no problem, but when I build it won't run because the native dlls are not brought to the final target. I solved this by adding some post build actions to copy the native dll and pdb files. This works, and I'm able to run the code with no errors. However, I'm unable to debug the native project. I hit breakpoints in the C# project and CLR projects, but not the native project.
What I have tried:
In the C# project properties I have enabled the native code debugging option.
In the CLR project I have set debugging mode to mixed.
In the native project I have tried both native only and mixed debugging mode
In the C# project I have checked allow unsafe code
In visual studio under tools->options->debugging->general I have tried checking and unchecking use native compatibility mode and suppress jit optimization on module load.
I tried opening the native project in a separate visual studio instance to attach the debugger to the project running from the whole solution, but I was not allowed to do this as the solution debugger was already attached to that project. Someone suggested to do this, but didn't explain how this could be done.
The problem was that the C# project I referred to before was in itself a dll being called by another C# exe project. When I enabled native debugging for this project, everything worked as expected.
I have written a library in C that I want to be able to be used in C#, C++, and Python (other languages would be nice, but not necessary for now). The library was developed in Linux and I have been able to compile it on Windows via MinGW. The problem I am having is when trying to add the .dll as a reference in a Visual Studio 2010 solution. The error I get is:
A reference to 'C:\path\to\libmylibrary.dll' could not be added. Please make sure that the file is accessible, and that it is a valid assembly or COM component.
I have spent some time trying to see if I am compiling the DLL incorrectly, but don't see anything glaring out at me. Some references I've used are this, this, and this.
If more information is needed I can provide some compilable example source code.
There are 2 ways to add a "DLL" to a C# project.
If the DLL is a CLR Assembly, meaning it is managed code that adheres to the CLR, then you can add it as a "reference".
If the DLL is NOT a CLR Assembly, you can load the code manually using the P/Invoke structure. There's a lot of online documentation on P/Invoke. It is messy, but it works. You need to declare each DLL entry function using the [DllImport] attribute, and load the DLL manually. Search SO for p/invoke.
Based on your error message, you are trying to load a plain DLL as an CLR DLL. That means you'll have to figure out how to use P/Invoke.
I have been stump in this problem for a few hours now. I hope someone has had a similar problem to this.
We have developed a prototype .Net(C#) dll using VS2010, and would like to be able to call this dll in a both C# applications and VB6 application.
My question is:
Is it possible to debug a VB6 application that is calling a .Net dll? I get an error message "Automation Error The system cannot find the file specified"
The error message suggests that there is something missing for my VB6 app to find the .Net dll.
I am aware that if the VB6 application has been compiled, and the .exe has been created, the VB6 will successfully call the .Net dll functionality when using the .exe
However it is important that we can debug through our VB6 application. Unfortunately debugging does not allow you to step over the line of code instantiating the .Net DLL's class object. I can't seem to do this.
NOTE: I have looked around forums and MSDN documentation and I mostly find solution for calling a VB6 dll in .NET; which is unfortunately the opposite of what we need to do.
NOTE: I have already registered the compiled .Net(C#) assembly, and referenced it in the VB6 project.
I have however found these two pages, which seemed to be what we need, but its a solution for calling a .NET(c#) dll generated using VS2005. This doesnt seem to work when the .NET(C#) dll was generated using VS2010.
site1
site2
If someone could give any suggestions or direct me somewhere I can get one, that would be great.
Thanks
SOLUTION
Thanks to #HansPassant, I have found the solution.
To debug a VB6 project that contains a C# .NET assembly, you need to register the .NET dll through both "regasm" and "gacutil", then make sure to close and reopen the VB6 application before you start debugging.
This is not a problem, VB6 uses its own debugger that doesn't get in the way of any other debugger, including the managed one for C# code.
You start from your C# class library project, ensure it is selected as the start project. Project + Properties, Debug tab. Select the "Start external program" option and enter the path to the VB6 IDE. Typically c:\program files\microsoft visual studio\vb98\vb6.exe. Set a breakpoint on the method you want to debug.
Press F5 and the VB6 ide will start running. Load or create your vb6 project. Note how you can add the path to the .vbp project in the previous step so it will automatically load your project.
Start debugging your vb6 project as usual. As soon as it starts using your [ComVisible] C# class then your C# assembly gets loaded. And the breakpoint will hit when your vb6 code calls the method. Switch back and forth as needed. Note that you cannot single-step from vb6 to C# code, you have to set breakpoints to get the debugger to stop.
Ah, the wonders of using .NET from VB6 in a debuggable manner.
in the VB6 project compile options (reached using the Options button on the Make Project dialog window), choose the Compile to Native Code, No Optimization, and Create Symbolic Debug Info options. Then compile your VB6 project. These options allow proper VB6 binary-to-source mapping.
Go to the Configuration Properties...Debugging property page of your solution and change the Start Action to launch your VB6 executable.
In VS Solution Explorer, go to File...Add Existing Item and navigate to the folder containing the VB6 source code you want to debug. Double-click on the VB6 source code file you want to debug, and a source window should open in VS that allows you to set breakpoints in the VB6 source code.
Make sure that your .NET library has a public default constructor. This is essential.
Now also set any C# breakpoints that you need. Do not step into the .NET code - this doesn't work.
When you start debugging with VS, your VB6 and C# breakpoints should be hit normally.
One approach is to debug each individually:
Debugging the VB6 code can be done in the IDE after compiling the C# DLL and adding it as a reference to the VB6 project.
Debugging the DLL with the VB6 host is possible in Visual Studio by compiling the VB6 project and using it in the project properties as the executable to run.
In some cases this is simpler/quicker than setting up the environment to debug both simultaneously.
This approach will require having at least the framework of each working beforehand.
I have a C++ solution. The startup project is an exe. In the solution there are a number C# dlls (targeting .NET Framework 2.0) that are registered for COM interop. When I put a breakpoint in the C# code I get the hollow red breakpoint with "No native symbols in symbol file"
I have tried setting Project Property Pages -> Debugging -> Debugger Type to Mixed on the start-up project that calls the COM methods.
I have checked Debug -> Windows -> Modules. It has loaded my dlls, and the symbol status is "No native symbols in symbol file".
This is not the end of the world because if I do Debug -> Start Without Debugging and then Debug -> Attach to Process, changing the Attach To: to Managed (v2.0, v1.1, v1.0) code, Native code. Then I hit breakpoints in both the C++ code and C# code.
So I have my workaround but I reckon if I can do it by attaching to process - I should be able to do it by just debugging.
How can I hit my C# breakpoints by just doing Debug -> Start Debugging?
I was able to debug my C# dll from a C++ project in VS2008 by doing the following:
In the C++ project's properties, goto Configuration Properties -> Debugging. Set "Debugger Type" to Mixed. "Attach" should be set to No.
In your C# project properties, in the Debug tab, set the "Start External Program" to your C++ project's executable.
I know it's a little bit old but I found a practical solution for the problem.
I had the same problem while using a C++ application which uses a C# COM-Object. I tried several settings within Visual Studio on the C++ and C# side. Nothing helps until I tried manually launching the Debugger.
You can use
Debugger.Launch();
to manually start the Debugger on your C# DLL. I know this is not the best but a practical way. In later productive environments you have to remove the Debugger launch function :).
Regards
I am unsure if this will help but we work a lot with C# and C++. I found this to be possible by placing the C++ project and the C# project in the same solution and enabling "native debugging" in the C# project. Then I was able to jump back and forth between them while debugging.