I am developing an application that communicates with some hardware using the C++ DLL provided by the hardware provider. I also have a header file for this DLL, but no source file. In my C# application, I'm trying to import and call the DLL's functions like this:
public class MyClass
{
[DllImport("CaGe.dll")]
public static extern long someLibraryFunction();
public void callLibFunction()
{
Console.WriteLine("function call: " + someLibraryFunction());
}
}
The library.dll file is located in the same folder as the MyClass.cs file and also the rest of the project files. When I start the debugging session however, I first receive a dialog window from system saying: CAGE InitDll: Erro on load library "CdbClientInit" and after I click OK on that, an unhalted exception on the line where I call the library function occours.
The exception says: System.DllNotFoundException: Exception from HRESULT: 0x8007045A
I found on the internet that this may be caused by a missing DLL that the CaGe.dll needs, so I tried to put the DLL through the Dependency Walker, but the results are a little bit confusing for me. Under the CAGE.DLL there are WS32_32.DLL, VERSION.DLL, KERNEL.DLL and USER32.DLL tabs, I susspect that the libraries I need are somwhere under the USER32.DLL tab, but I don't recognize any of them (if a missing DLL is what is causing this problem).
Any advice would be much appretiated :)
More help to use C++ function in C# please check below URL
http://www.codeproject.com/Questions/107152/Using-a-C-dll-in-a-C-application
Related
I have a C# project which is a library I reference in one of my C# tests I have:
myproj
|-bin
+-External
| |-pHash.dll
|-main.cs
|-MyClass.cs
|-myproj.csproj
pHash.dll is a Visual C++ library (compiled using a vcproj project, so we are talking about Microsoft C++ flavor) called phash which exposes this method:
int ph_dct_imagehash(const char* file, ulong64& hash);
I want to use this method from MyClass.cs. So I do this:
public class MyClass {
[DllImport("pHash.dll")]
static extern int ph_dct_imagehash(
[MarshalAs(UnmanagedType.LPStr)] string file,
[MarshalAs(UnmanagedType.U8)] UInt64 hash);
public MyClass() {...}
public DoStuff() {
UInt64 outputValue = 0;
ph_dct_imagehash("a string", outputValue); // The second parameter should be a pointer in the C++ implementation, not really sure if I am doing it right here
}
}
In my project, I set External/pHash.dll to be Content and also set it to be Always copy in the output folder.
A possible mistake As I pointed out, the way I use ph_dct_imagehash might be wrong, but this question is about a different error I get, so please skip this and move on :)
MyClass is then referenced in one of my tests I execute using MSText.exe.
The error
When I try to run my test which is using that class I get:
System.DllNotFoundException: Unable to load DLL 'pHash.dll': The
specified module could not be found. (Exception from HRESULT:
0x8007007E)
What am I doing wrong?
Second attempt
I saw that, when building, actually my bin folder looks like this:
myproj
+-bin
|-External
|-pHash.dll
So I thought I had to change the path to the DLL:
public class MyClass {
[DllImport("External/pHash.dll")]
static extern int ph_dct_imagehash([MarshalAs(UnmanagedType.LPStr)] string file, [MarshalAs(UnmanagedType.U8)] UInt64 hash);
...
}
But then I get:
System.DllNotFoundException: Unable to load DLL 'External/pHash.dll': The
specified module could not be found. (Exception from HRESULT:
0x8007007E)
Another question
Is there a (maybe debugging?) tool to understand what path is the CLR trying to follow when encountering DllImport? So at least I know where it is trying to look for that dll...
More info
I have been asked to inspect my dll, so by using DependencyWalker on pHash.dll, I get this error:
Error: The Side-by-Side configuration information for
"c:\myuser\testresults\myuser-0131
2016-05-06 08_56_50\out\PHASH.DLL" contains errors. The application
has failed to start because its side-by-side configuration is
incorrect. Please see the application event log or use the
command-line sxstrace.exe tool for more detail (14001). Error: At
least one required implicit or forwarded dependency was not found.
Error: At least one module has an unresolved import due to a missing
export function in an implicitly dependent module. Error: Modules with
different CPU types were found. Warning: At least one delay-load
dependency module was not found. Warning: At least one module has an
unresolved import due to a missing export function in a delay-load
dependent module.
This error is also reported in the stack trace when I run my test. I thought it was a message coming from MSTest about something else, but now I realize it is a problem of this DLL!
Even if your DLL is found (sits in the test directory), it is still reported as missing when some of it's dependencies are not found. Make sure you copy the DLL itself and all DLLs it depends on.
You can set select your dll in Solution Explorer, right click on it and set BuildAction to Content and Copy To Output directory to CopyAlways. That way your dll will be copied to application directory and DllImport should find it.
Alternatively, use DllImport's SetDllDirectory with DLL path before first call of your imported dll
[DllImport("kernel32.dll")]
static extern bool SetDllDirectory(string yourPath);
Update
I have now run through the tutorial 3 times with the same results (Visual Studio/Windows is unable to recognise the DLL as a valid file). This must be an issue with my environment, as mike below ran through the tutorial and it worked fine.
I did notice this in the C++ project's solution explorer on my last run:
Does anyone know if this is okay? There seems to be a lot of Red stop-signs which to me would suggest something bad...
Following this tutorial, I have ended up with the following:
C#
using System.Runtime.InteropServices;
namespace TestImport
{
class Program
{
[DllImport("TestLib.dll")]
public static extern void DisplayHelloFromDLL();
static void Main(string[] args)
{
DisplayHelloFromDLL();
}
}
}
C++
In .cpp file Source Files
#include <stdio.h>
extern "C"
{
__declspec(dllexport) void DisplayHelloFromDLL()
{
printf("Hello from DLL !\n");
}
}
When debugging in Visual Studio:
An unhandled exception of type 'System.DllNotFoundException' occurred in TestImport.exe
Additional information: An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)
When running the built EXE (from he same folder as the Dll):
An attempt was made to load a program with an incorrect format.
Have I done anything wrong in the above code?
I did do all of this in VS 2015, where the tutorial calls for VS 2010, howeve rI couldn't find a more up-to-date tutorial.
When I try to add the project as a reference by Project -> Add Reference ... I am seeing this error:
A reference to 'Path\To\MyLib.dll' could not be added. Please make sure
that the file is accessible, and that it is a valid assembly or COM
component.
Which makes me think that the issue is either with the source code or the DLLs configuration.
I have also tried building both files and putting them in the same folder before running the Executable, but without any improved results (same error as when running the EXE above).
Solution Explorer Screenshot:
Make sure the name of your C++ project and DllImport parameter are the same. Also, if the dll file is not located in the same directory as your C# project, make sure to add the dll into your Debug/Release folder.
Also! Make sure that you are running in the same 32/64 bit mode when compiling.. if you compiled the dll using 32 bit and try to use it in a 64 bit C# program, it won't work.
OK, now build this application, and then copy the previously built DLL into the Debug/Release directory of the current application. The DLL should be in the same directory as your main application.
Did you do the bolded text? Your C# app won't know where to look for the DLL and it looks in the build folder, by default.
An unhandled exception of type 'System.DllNotFoundException'
It happened to me, because of the imported c++ dll, its own dependency dlls were missing.
After copying them into Debug/Release folder everything worked.
I have a program written in C#. I want to use a DLL made in C within this program.
public class Test
{
[DllImport(#"C:/.../surcouche2.dll")]
public static extern int refreshEntities();
}
I call the function as:
Test.refreshEntities();
I am using Visual Studio. To create the DLL surcouche2.dll, I created a new Visual C++ Application Console, then I chose DLL and left the options on their defaults. Then, I told to VS to compile using C.
The function is :
__declspec(dllexport) int refreshEntities() {
int ret = 0;
LibData *n;
n = newLibData(LIB_MODULES_MODULE_ENTITES, LIB_MODULES_ACTION_SELECT,
"http://10.0.2.2:4242/WebService1.asmx");
if (n)
{
ret = n->refreshDb(n);
n->destroy(n);
}
return (ret);
}
The functions called in are in another DLL (that is referenced). But I get this error:
system.DllNotFoundException: Impossible de charger la DLL 'C:/.../surcouche2.dll': Le module spécifié est introuvable. (Exception de HRESULT : 0x8007007E)
à app.Lol.refreshEntities()
à app.MainWindow..ctor() dans c:\...\MainWindow.xaml.cs:ligne 30
But, if I change the function refreshEntities like this, then it works fine:
__declspec(dllexport) int refreshEntities() {
return (42);
}
The second DLL uses another DLL (both in C). I created them with the option "create an empty project" so I haven't the stdafx.h, ... files. I guess it's not a problem because I can use a function from the third DLL in the second one.
This error can happen if a dependency of loaded dll can't be resolved.
First of all I propose you to put both native assemblies in a bin folder and change a reference
from [DllImport(#"C:/.../surcouche2.dll")] to [DllImport("surcouche2.dll")]
In general to debug dependency issues tools like Dependency Walker and Process Monitor can be useful. First helps to understand what the dependencies are, second to check there your application is trying to find the assemplies.
Configure Process Monitor's to show process activity only and apply process name filter with your application name like on the picture below and you will get all files your app trying to access. It will help to find missing dll's.
[DllImport(#"C:/.../surcouche2.dll")]
This is bad idea, you are getting a preview of what is going to go wrong on your user's machine as well. Hard-coding the path to the DLL like that helps the pinvoke marshaller to find the DLL file on disk. But it does absolutely nothing to help the operating system to find DLLs that surchouce2.dll needs. Like the one that contains the newLibData() function.
The error message is often mis-interpreted. It says it "cannot load" surcouche2.dll. Which is accurate, but most programmers will read the message as "cannot find" surcouche2.dll. The most common reason for the exception. Not the problem here.
Never mess with DLL Hell. The days that keeping DLLs in a separate directory and sharing them between different programs was useful are long, long gone. Always copy dependent DLLs into the same directory as the EXE that needs them. Makes it very easy on the operating system to find them. And avoids the considerable misery you'll have to deal with when it finds the wrong file.
Use Project + Add Existing Item and select the DLLs. Set their Copy Local property to True. If you don't like the clutter then use XCOPY in a post-build event.
I get following error message (VS2010) when running in debug mode my C# WPF appliction:
"Unable to load DLL 'VCECLB.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)"
The code where this error occurs is (see hDevEnum):
namespace Imperx.FLExGrabber
{
public class Enumerator:IEnumerator
{
private IntPtr hDevEnum;
VCECLB_EnumData enumData;
/// Default constructor
public Enumerator()
{
enumData.cbSize = (UInt32)Marshal.SizeOf(enumData);
// Open enumerator handle
hDevEnum = NativeFunctions.VCECLB_EnumInit(); <<--- Error message here!!!
}
/// Destructor
~Enumerator()
{
NativeFunctions.VCECLB_EnumClose(hDevEnum);
}
}
}
From the existing project, which uses a windows form application, it runs perfectly. Now I need to transfer this solution into a WPF-application. Therefore I am using the same machine (Win7/64ibt) with the same VS2010. The platform target is X64.
Question: Where I need to add the VCECLB.dll file into my project? I can not add it under references and therefore I put it into the folder "...\bin\x64\Release" - but no success.
When I check the VCECLB.dll with dependency walker I get following:
Does the question marks means that those dll's are missing? If so, why I can run the windows form project with the same VCECLB.dll?
Does anybody know how I can solve this issue?
Thanks in advance
There are two common causes for such an error:
The DLL that you are referring to is not on the DLL search path, or
The DLL that you are referring to is found, but its dependencies cannot be found.
Resolve problem 1 by putting the DLL in the same directory as the executable. Resolve problem 2 by making sure that all dependencies are installed. Typically this involves deploying the MSVC runtime that the DLL depends upon.
You can put your VCECLB.dll any where in your solution (in root for example by Drag & Drop)
Then, once you added the file, click right on your file, choose properties
In Advanced three:
Choose content in Build Action
And Always copy in Copy to output Directory
to get something like the follwing:
In my project I have an unmanaged native C++ dll and a C# application. I am trying to import a function from the unmanaged dll using DllImport but I keep getting a DllNotFoundException.
Here is my code that calls the DLL.
using System.Runtime.InteropServices;
namespace TestApp
{
public delegate void UpdateDelegate(string s);
class Program
{
[DllImport("CGPUnmanagedLibrary.dll")]
internal static extern int parse_raw_gsod_file(
[MarshalAs(UnmanagedType.LPStr)]
string filePath,
int minTemp,
UpdateDelegate callBack);
static void Main(string[] args)
{
UpdateDelegate myCallBack = new UpdateDelegate(Program.Report);
string path = #"C:\Creative Solutions\Projects\Clyde's Garden Planner\Frost Data Database\GSOD Data\GSOD_RAW_DATA\1992\gsod_1992.txt";
int result = parse_raw_gsod_file(path, 32, myCallBack);
Console.Write("Parse completed with exit code: " + result.ToString());
Console.ReadLine();
} // end main function
public static void Report(string msg)
{
Console.Write("Message is ");
Console.WriteLine(msg);
}
} // End class
} // end namespace
I tried copying the DLL to the app output directory but it still can't find it. I also tried adding the DLL project as a reference but I get a popup window saying it can't be added. How do you properly link an unmanged DLL to a managed application?
Update - Here is the full error:
Unable to load DLL 'CGPUnmanagedLibrary': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
Update 2 - I know for sure that the DLL is in the same directory as the .exe trying to load it. This makes me think there is a dependency in the DLL that isn't getting loaded. I'm only using basic C++ libraries in the DLL (string, math, iostream, etc). Any ideas what could not be loading and why?
Update 3 - Tested with Dependency Walker
Loading my unmanaged C++ DLL in dependency walker showed no errors. I also tried to open my executable in dependency walker and it showed errors loading two DLLs: GPSVC.DLL and IESHIMS.DLL - doesn't make any sense because I am only using standard c++ libraries in my code. I think it may have something to do with the fact that I have a managed C++/CLI DLL trying to load the unmanaged DLL as well (I was trying to implement some C++/CLI wrappers). Anyway, I have since started a new VS solution and moved on. See my answer.
In all likelihood the problem isn't the DLL you're trying to load but one of its (chained) dependencies. Run depends.exe or a similar utility on the DLL to see if all the dependencies can be found. The misleading message "The specified module could not be found" has become a classic annoyance (if not FAQ material!): it leads you to think that your DLL is not being found when almost all of the time it's one of its dependencies that's not being found.
To test, the *.dll needs to be in the same directory as the .exe that is trying to load it. Don't trust Visual Studio to do it for you at this point. Physically copy the file to C:******\Debug\x86\bin\ or whichever configuration you are running under. If in doubt, copy it to all of your bin folders. After you figure out the path, then you start finding ways to automate the project build to copy the file correctly. If that doesn't do it, put it in system32--it will certainly find it there. However, if after doing these things, you still can't find it. There is probably a dependency to your unmanaged dll that is also missing.
First I want to thank everyone for their help. Unfortunately I never did solve this issue (see edits in my main question). The answer turned out to be starting a totally new Visual Studio solution and creating two new projects: C# app and C++ dll. I did away with the need for wrappers as I am now just marshaling two main functions.
Thanks again.
The anwer of user arayq2 made much sense and I was quickly able to solve my problem also.
The dll that couldn't be loaded (DllNotFoundException) in my case is depending upon another dll. This dll (that is not part of my project) was actually compiled with newer versions of certain .h and .lib files. Older versions of these .h and .lib files (with the same filename) were part of the project that compiled the dll that couldn't be loaded.
After I updated my dll project with the newer versions of these .h and .lib files and recompiling my dll project, my problem was solved.
Thank you arayq2!