I have a C# application and a C++ DLL, both x86. The Application is the startup project, the DLL project is inside the same solution and is referenced as a project. The C++ DLL outputs its PDB file with the same name as the DLL inside the Debug folder of the Application.
I have a function called SomeFunction that I'm trying to execute in C#. When the code reaches that line, it stops there. The UI of the C# application continues to be responsive, but the breakpoint never leaves that line (and that's in Form_Load).
If I try to set the DLL as startup project and tell it to execute the C# application, then C# will crash at that line with: System.EntryPointNotFoundException: Unable to find an entry point named 'SomeFunction' in DLL 'SomeDLL.dll'.
This is the declaration of the function that I'm trying to call:
[DllImport("SomeDLL.dll", EntryPoint = "SomeFunction", CallingConvention = CallingConvention.Cdecl)]
public static extern int SomeFunction(IntPtr hwnd);
This is the function's declaration from the C++ header:
#define MYDLL_API __declspec(dllexport)
MYDLL_API extern int SomeFunction(HWND hWnd);
This is how I call it from C#:
var someAnswer = SomeFunction(_hwnd);
UPDATE: since the discussion below could take some time to read, here's the answer in the nutshell: I was missing an extern "C". Also, in order to debug the DLL (which was also a problem), the project needs to support native debugging both from C++ and C#, here's an excellent list that I went through and at the end it was all good!
No Symbols loaded in mixed C# C(win32) project using VS2010
Run code that calls SomeFunction to ensure unmanaged .dll is loaded
Go into Debug -> Windows -> Modules and check the .dll path and symbols status. You can try to load symbols in context menu of your c++ dll in that window.
(very often happens that .net loads different (not expected) version of unmanaged .dll)
Now I'm pretty sure that the problem is that your exported function name is mangled.
Try to define function like this:
extern "C" MYDLL_API int PASCAL SomeFunction(HWND hWnd);
In C#:
[DllImport("SomeDLL.dll")]
public static extern int SomeFunction(IntPtr hwnd);
I suspect the problem that it won't set the breakpoint beforehand is that the DLL is loaded on demand via p-invoke. If VS doesn't think the DLL is a dependency, it may not allow you to set the breakpoint beforehand.
You could add a DebugBreak to your c++ code. Then simply run your app, don't debug it. Then when it executes this statement, you will get a Just in time debugging alert allowing you to jump into the c++ debugger.
C++ as startup
Alternatively, you could make the DLL the startup project, but change the debug settings so that it launches an external process - in this case your app .exe.
This time however, you don't need the DebugBreak(), just a regular breakpoint.
Now when you debug, your DLLs symbols are loaded thus allowing the break points to work.
I used this trick a lot with ActiveX/COM.
Related
I'm building a Keygenerator application with .Net Maui (not blazor).
For this i use c#-Code in the MainPage.xaml.cs that calls a cpp .dll file and imports some methods.
The import looks like this:
[DllImport("W5R._Keygen.dll", CallingConvention = CallingConvention.StdCall)]
internal unsafe static extern void
SHA256_calc(byte* hash, void* input, ulong inputlen);
The .dll is in the same folder as the MainPage.xaml, App.xaml etc.
By changing some properties of the .dll (Build = content) the Debug version on the Windows Machine works fine and it works exactly as it should.
HOWEVER:
and this is the problem:
when I run the application on the android-emulator it loads the app just fine and as soon as i press a button that invokes the usage of the .dll my App Crashes and it just stopped working.
Beforehand I had the error ".system dll not found" which i fail to reproduce in the current moment.
Anyone knows how I use the .dll library? It's cpp code that i cannot access.
You can't use a dll on Linux / Android.
Dll are a windows thing and Linux has other formats for shared libraries.
see this Post
It seems there exists a wine release for Android, but I don't know how its used.
I'm trying to import a C++ Project Dll into a C# project. I found a lot of people talk about using DllImport. I tried using that and here is what I have-
CPP Code:
int __declspec(dllexport) beginCode(double reportId);
C# Code:
[DllImport("C:\\Users\\<my_user_id>\\Desktop\\ctxmix\\Release\\ctxmix.dll",CallingConvention =CallingConvention.Cdecl ,CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
public static extern int beginCode(double reportId);
int result = beginCode(reportId);
But when I run, I'm getting an exception - Exception thrown:
System.DllNotFoundException
Do I have to add any references for the CPP Dll in the project or do anything else apart from the code which I have on the top?
Edit: I'm trying to run my .exe using VS2015 and I get this exception on my local machine. Also, I don't see my CPP Dll in the Project->References section where as I see other references there.
The unmanaged DLL needs to be locateable by your managed process. Typically that means placing the DLL in the same directory as the executable file. But you gave used an absolute path which I presume you transcribed correctly.
You may also encounter this error if the DLL's dependencies cannot be located. That seems the likely explanation here. Most likely the MSVC runtime cannot be located when your DLL is loaded.
Using an absolute path isn't a great idea. That will break down when you distribute to another machine. Use just the DLL file name and place it in the same directory as the executable.
Your DllImport attribute seems fussy. No point specifying CharSet when there is no text. I doubt your function calls SetLastError. And do you really need ExactSpelling?
I am aware of this similar question, but it does not respond to my problem.
I have written two .dlls using Visual Studio 2010. One is in C++, and communicates with an SDK that was written in C++. The other is a C# wrapper for that C++ library, so that it can be used in C# contexts.
My plan was that this would let me use my code in Unity3D, but apparently that is not the case. It seems like Unity3D does not allow me to import .dlls as Assets if they are not a .NET assembly. So I can add my C# wrapper, but not the C++ dll.
This results in a DllNotFoundException whenever I try to access the C++ library. I have tried simply copying the C++ library into the Assets/Plugins folder, but that gives the same results.
Is there a way to do this properly? This is a very vital part of my project setup.
The problem is that the DLL is not being found when the p/invoke runtime code calls LoadLibrary(YourNativeDllName).
You could resolve this by making sure that your DLL is on the DLL search path at the point where the first p/invoke call to it is made. For example by calling SetDllDirectory.
The solution that I personally prefer is for your managed code to p/invoke a call to LoadLibrary passing the full absolute path to the native DLL. That way when the subsequent p/invoke induced call to LoadLibrary(YourNativeDllName) is make, your native DLL is already in the process and so will be used.
internal static class NativeMethods
{
[DllImport("kernel32", SetLastError = true, CharSet = CharSet.Unicode)]
internal static extern IntPtr LoadLibrary(
string lpFileName
);
}
And then somewhere in your code:
private static IntPtr lib;
....
public static void LoadNativeDll(string FileName)
{
if (lib != IntPtr.Zero)
{
return;
}
lib = NativeMethods.LoadLibrary(FileName);
if (lib == IntPtr.Zero)
{
throw new Win32Exception();
}
}
Just make sure that you call LoadNativeDll passing the full path to the native library, before you call any of the p/invokes to that native library.
Note that the DllNotFoundException can be caused by building your Unity DLL in Debug instead of Release!
A simple oversight that can cause a headache.
This also happens when Unity can find your DLL, but is not able to find it's dependencies. Obvious fix is to place dependency DLLs into /Plugins as well, or link your dependencies statically.
Less obvious reason is when your DLL depends on Visual Studio runtime library dynamically, i.e. is built with Properties -> C/C++ -> Code Generation -> /MD option. Change it to /MT to link with runtime statically.
Background
I have an embedded system which runs an application originally written in C++ and compiled in Visual Studio, which results in a single executable and more than 30 DLLs. These libraries cannot be browsed in VS Object Browser or other tools such as P/Invoke Interop Assistant.
Loading some of the DLLs in Dependency Walker shows that all of them are missing some dependencies deep in their dependency tree (cdfview.dll, dwmapi.dll, w32topl.dll, ...) but according to this question, that is likely not an issue.
I have some of the source code files, and all of the compiled DLLs. The application currently runs without issue, indicating there are no real dependency issues.
I am trying to call some library functions and eventually make a wrapper using C#, but am unable to successfully import and call even the simplest of functions. I always receive the following error:
Unable to load DLL 'dllName.dll': A dynamic link library (DLL)
initialization routine failed. (Exception from HRESULT: 0x8007045A)
Sample Code [EDITED]
From the C++ source code header file I have the following declarations:
#define OB_API __declspec(dllexport) __cdecl
typedef unsigned long DWORD; // From windef.h
typedef DWORD OBSTATUS;
OBSTATUS OB_API TestObj(void);
In the C++ source code file the following definition is given (which would seem to always return true):
BOOL WINAPI DllMain(HANDLE /* hModule */,
DWORD ul_reason_for_call,
LPVOID /* lpReserved */
)
{
switch (ul_reason_for_call)
{
case DLL_PROCESS_ATTACH:
case DLL_PROCESS_DETACH:
case DLL_THREAD_ATTACH:
case DLL_THREAD_DETACH:
break;
}
return TRUE;
}
In my C# application class, I add the following declaration:
[DllImport(#"dllName.dll", CallingConvention=CallingConvention.Cdecl)
public static extern ulong TestObj();
The DLL and C# application binary reside in the same directory.
Questions
From researching the error, it seems there is a large number of reasons this particular exception could be thrown and I was wondering how I could further troubleshoot this type of issue.
Is there any way to get more detailed information on why the initialization routine failed?
(Note: target system is running .NET framework 2.0)
The DLL you are loading contains a DllMain() function. That's pretty common, such a function initializes the state of the DLL. Windows makes sure that this function is called whenever the DLL gets loaded, it will happen automatically the first time you pinvoke a function exported by that DLL.
Problem is, that function returned FALSE to indicate that it could not properly initialize the DLL. That of course does not give a wholeheckofalot of information about why it returned FALSE. Windows can't do anything but generate error 1114, ERROR_DLL_INIT_FAILED. If the DLL itself doesn't output any diagnostic then you can't do anything but debug the code. Start with Project + Properties, Debug tab, tick the "Enable unmanaged code debugging" option.
Fingers crossed that you see a message in the Output window. Odds are not very good. If you don't have the source code for the DLL then you'll need the help of the vendor or author of the DLL. Give him a copy of a test project that fails like this.
Maybe the reason is need to install old Net Framework version like 2.0, 3.0, 3.5,....it's worked for me :D
I got a DLL that I want to add to my C# project and I have some problems. First, my DLL is coded in C++ and I got an interface of one function to export it.
extern "C" __declspec(dllexport) char* sniff()
{
return ps.Sniff();
}
I have an instance "ps" that initialise a socket when the DLL is attached. The point is that I need to have this instance initialise when I call my exported function. My problem is when I import it in my C# project, my DLL is detached for no apparent reason and I can no longer call my exported function.
I use this syntax in my C# projet :
[DllImport(#"C:\Documents and Settings\Pat\Bureau\sniffoporn\Release\sniff.dll", EntryPoint = "sniff", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr sniff();
Some important things that I tryed :
Import the DLL in the reference of the project : Can't because it's not a COM component.
Manually import the DLL using LoadLibrary, FreeLibrary and GetProcAddress : Same result
Call my exported function in loop : Same thing but the DLL is attached for a little longer before detaching.
I would want to know why my DLL is detaching and how can I keep it attached for the rest of the process life.
Thanks a lot
Maybe an exception occurs in your DLL itself. Making it detach in Visual Studio to prevent your application from crashing. After all C# is managed code.
Try your same procedures with a different (dummy) dll with very simple functionality. If it still occurs then something with your method is wrong, otherwise with the DLL you are attempting to use.