I have created a dll in C++ using a Class Library project in Visual Studio. I need to call a method in the dll from a C# application.
I got to know there are 2 approches. One is to add the dll project reference to C# project or use DllExport to export method. However when I tried in both ways it always gives the following error when the dll method is called in runtime.
An unhandled exception of type 'System.BadImageFormatException' occurred in TestClient.exe
Additional information: An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)
Can i know how to avoid this problem ?
Thanks in advance!
This error means that you're trying to load a 32-bit DLL into a 64-bit process or a 64-bit DLL into a 32-bit process. On Windows, the bitness of the DLL must match the bitness of the process in order for it to load correctly.
Is your native DLL 32- or 64-bit? In your C# project build settings, what platform are you targeting? If you go into the C# project properties, you can go to the Build tab and change the "Platform target" to something specific like x86 or x64 to match the platform that your native DLL was built for.
The other alternative would be to build the native DLL to match the platform of your C# application. If the C# application's platform is AnyCPU, though, it will run as 32-bit on 32-bit Windows and 64-bit on 64-bit Windows. Because of this, you would need both a 32- and 64-bit version of your native DLL.
I would recommend setting your C# application's platform to something specific (x86, x64) and then change your native DLL's platform to match.
Related
I'm writing a program for embedded linux on an ARM processor in .net that uses mono to execute. I have found that I can simply compile to either x86 or x64 architecture on my PC, copy the Debug directory over to linux, and run the program using mono myProgram.exe. The program is working perfectly like this and mono seems to take care of the architecture mismatch. This was true until today when I tried to incorporate an external native DLL.
I have both an x86 and x64 bit architecture of the external DLL and both work on the desktop environment fine. I have a shim class that uses [DllImport] to load the extern functions. However, when I try this on embedded linux with Mono I am getting a BadImageFormat exception. My guess is that Mono somehow transitions the compiled DLLs in the exe at start up but doesn't do the same for the external.
Some other info:
1. I don't have source for the native external library. I have x86, x64, and a .so library.
2. I have tried making a manage C++ shim that accesses the .so but can't get it to compile on the desktop since windows doesn't recognize the .so file.
Some thoughts:
1. Is there a way to embed the native DLL into a managed so that Mono will transition the native DLL too?
2. Can I link the .so file to a managed C++ project?
3. Is there a way to tell Mono to incorporate that Dll during execution?
Ultimately I'm looking for a solution that is wrapped in the exe that allows me to simply run it like I did before and control the native system.
If you have all the .dll and .so files for Windows and Linux, you can probably use dll maps feature of Mono. (https://www.mono-project.com/docs/advanced/pinvoke/dllmap/) which are used to map Windows dll names to Linux so names.
.Net does not recognize this, but Mono does.
I've read many questions and answers indicating that if I want to link my C# project against native libraries, I can't use AnyCPU platform target but must make separate 32- and 64-bit builds, each linked against the native DLL of the appropriate bitness.
This makes me wonder how the .NET Framework assemblies themselves are, or at least appear to be, built for AnyCPU. That is, when adding a reference to my GUI application, why don't I have to pick the 32-bit or 64-bit version of System.Windows.Forms? I thought this might just be some Visual Studio magic that would resolve to the appropriate GAC subdirectory (GAC_32 or GAC_64), but I searched for System.Windows.Forms.dll in the GAC and found it in:
C:\Windows\Microsoft.NET\assembly\GAC_MSIL\System.Windows.Forms\v4.0_4.0.0.0__b77a5c561934e089\System.Windows.Forms.dll
Note the "GAC_MSIL". So how does this DLL manage to wrap a native 32-bit API yet remain linkable in a 64-bit application? And why can't I use a similar strategy to make a single C# DLL that links against a native 32-bit library yet remains runnable in 64-bit mode?
Option 1: In GAC you may register 2 versions of assembly one 32 and one 64 bit with exactly same names. Oracle DB Driver for .NET uses this strategy.
Option 2: With your assembly that will be AnyCPU deploy two versions of native DLL and choose proper DLL at runtime (SQLite works like that). As it turns out .NET Framework is intelligent enough to load proper version of native DLL via P/Invoke (Using a 32bit or 64bit dll in C# DllImport)
I had the same problem and ended up using Fody Costura
DLL Files will be shipped as embedded ressources and the lib takes care of the bitness.
You could find an example for SQLite here
The problem I have encountered was that your application needs to have access to the Windows Temp folder to create the assemblies from the ressource. If you dont need it, you could disable it using a config setting createtemporaryassemblies
I have a DLL exception I am encountering:
response threw exception: Could not load file or assembly or one of its dependencies. An attempt was made to load a program with an incorrect format.
I have all source code for the following DLL/library combinations. I am trying to figure if I have a strange combination or what I need to check to ensure this runs. I have a native C++ code in a static library which is called by a managed C++ CLR supported DLL. Everything seems to work fine until the following point.
I created a test C# EXE console application to call the managed C++ CLR supported DLL. This works as expected. The difference where the exception is thrown when there is a C# Class library calling this same managed C++ CLR supported DLL. Is this supported at all or is this the reason why the exception gets thrown? If this combination is incorrect, is there any workaround to get a C# Class DLL to call the managed C++ CLR supported DLL.
Everything is created with Windows 7 64 bit with Visual Studio 2012. All projects are in Release mode with x64 bit platform selected.
In every case I've seen, this is where a 32-bit C# app is trying to load a 64-bit C++ or C++/CLI DLL or a 64-bit C# app is trying to load a 32-bit C++ or C++/CLI DLL.
The next step I usually take is to use Dependency Walker to load the C++/CLI dll. Dependency walker will show you what DLLs your DLL is trying to load. In some cases I've had a 32-bit DLL with the same name as a 64-bit DLL appear in the Path first, hence it tries to load the wrong DLL.
Note that Dependency Walker will show a 64 on the icon next to 64-bit DLLs and will show a message along the lines of: "Error: Modules with different CPU types were found." in the info box at the bottom
my best bet is that the c++ dll is compiled as win32 your c# dll is set to Any CPU and you are running on a 64 bit system...
I've got a C# 2.0 project which is set to target 'Any Cpu', however it is referencing a C++ project that's building a 32 bit dll.
When I try to run my program on a 64bit machine I get the following error:
System.BadImageFormatException was
unhandled Message: Could not load file
or assembly TreeTMHook,
Version=1.0.2889.19619,
Culture=neutral, PublicKeyToken=null
or one of its dependencies. An attempt
was made to load a program with an
incorrect format.
How can I fix this?
Update
I want to be able to keep the main project as any cpu.
Thanks.
You'll need to build your .NET project as 32bit (x86 target) if you want it to correctly load a 32-bit DLL on a 64bit machine.
RE: Update:
If you want to keep your project as "Any CPU", you'll need a 32bit and a 64bit version of the DLL, and make sure the appropriate version is distributed with your app. If you can't build the other project as 64bit, you must build your .NET project as 32-bit only.
You will have to force your EXE project to run in 32-bit mode so it can use that C++ DLL. Project + Properties, Build tab, Platform Target = x86.
You may want to take a look at this article it explains why it is not possible, in short since you are dealing with pointers when accessing unmanaged code.
To keep you main project as Any Cpu, you need to supply both 32 and 64 bit version of the .dll - which should be possible, seeing as you're building it from source.
You then need to supply the executable with a manifest pointing it toward to right dll verion depending on platform.
Please use .net reflection and consume objects and its methods. Instead of direct 32 bit dll reference.
i have created a simple "public ref class" in the vc++ project, which is configured to generate a dynamik library.
In the c# Project (simple console application) i added the vc++ project as to the References and doing a "using myVC++library".
But when i try to create an object from the vc++ dll i always get: System.BadImageFormatException was unhandled
any clues or helpfull tutorials on this?
TIA
Is your c# project set to build for "Any CPU" - if it is, and you're on a 64-bit OS, then the load will fail.
The VC++ dll will be 32-bit only, and 64-bit app can't run it.
You could change your c# build to target x86 instead.