I have C++ DLL as below
#include "stdafx.h"
extern "C" __declspec(dllexport)double Add(double a, double b);
extern double Add(double a, double b)
{
return a + b;
}
n here m trying to link this DLL with my C# app
using System.Text;
using System.Runtime.InteropServices;
namespace test
{
class Program
{
[DllImport("DLL.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern double Add(double a, double b);
static void Main(string[] args)
{
Console.WriteLine(Add(1.0, 3.0)); // error here
Console.ReadLine();
}
}
}
m getting error:
"Unable to load DLL 'DLL.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)"
please help me out ...how can i link c++ dll with c# ?
The calling convention determines how function parameters are placed on the stack prior to a function invocation, and how they are removed (caller vs. callee) when the function returns. You can find out much more about this in about a million StackOverflow questions, or goto here and read up a little.
Regarding placement of the DLL within reach of the C# (aka .NET) application you're writing, I'm afraid I cannot comment on that except to say general DLL's must be in your lib-search path (PATH in Windows) the current directory, or the kernel's home directory (generally c:\windows\system32. Do NOT copy files to system32, btw. just setup your application to "run from" the directory where your DLL is residing and you should be fine. There are exceptions to this, and configuration settings that can radically alter this, but were I you i'd stick with simple for now. Complex can always come later.
You will either need to plant the dll in the same location as the C# exe or pack the dll inside the exe. The first option is simple enough. For the second option, check out Embedding DLL's into .exe in in Visual C# 2010
you got this error because DLL.dll wasn't in your Debug/Release Folder,
as far as i know visual studio doesn't know how to copy those files to your output folder manualy.
add the dll file to your C# solution
and then on files properties set build action to content
and set copy to output directory to copy if newer this will automate the copying
Related
I am new to PInvoke, I wanted to update my system volume using C#, I got one C++ dll and I have to just Import that DLL and use the methods to update the volume.
In C# I have written :
public const String DllName = "ChangeVolumeWindows.dll";
[DllImport(DllName, CharSet = CharSet.Auto)]
public static extern void SetSystemVolume(double newVolume, VolumeUnit vUnit);
I have put my dll into the exe path.
It is working fine for my pc , but when I package the app and send it to another machine I getting error " DLL not found "
I have observed that DLLImport is looking for path of my pc, which is not correct
For example:
I have put my dll in C:/User/ABC/Source/App/bin/debug/ChangeVolumeWindows.dll
in some another machine also it is looking for the same path instead of taking dll from C:/User/AnotherMachineUser/Source/App/bin/debug/ChangeVolumeWindows.dll
Can some one suggest where my code is going wrong.
I have tried to put my dll inside the project and the rebuild. Still I am facing the same issue.
Try this:
My.Application.Info.DirectoryPath("\folders\ChangeVolumeWindows.dll")
I'm writing an application composed by several modules written in different languages (i.e. Java, C#, C++).
I'm experiencing an odd behavior where the environment variables that I set in one module (e.g. C#) are not propagated to other modules.
As far as I understand, the problem is due to the fact that environment variables in Windows are accessed via the _environ struct in the runtime library, rather than via the process descriptor, hence libraries using different runtimes have different environment variables.
For C# in particular, this problem seems to occur only if I compile and run the code in Release, whereas compiling the code in Debug works just fine.
The code below reproduce the issue with two very simple modules written in C# and C++. I compiled the code with VS2015 Professional. C# code was compiled with runtime v4.0 and .NET framework v4.5.2
C# executable
using System;
using System.Runtime.InteropServices;
namespace ConsoleApplication1
{
class Program
{
[DllImport("cpp_lib.dll", CharSet = CharSet.Unicode)]
public static extern void print_path();
static void Main(string[] args)
{
var path = Environment.GetEnvironmentVariable("PATH");
path += ";D:\\Temp";
Environment.SetEnvironmentVariable("PATH", path);
// Print the path from C#
Console.WriteLine("Path from C#: " + Environment.GetEnvironmentVariable("PATH"));
// Print the path from c++
print_path();
}
}
}
C++ library
#include <iostream>
#include <Windows.h>
extern "C" {
__declspec(dllexport) void print_path() {
std::cout << "PATH seen in C++: " << getenv("PATH") << std::endl;
}
}
As stated before, running the code in Debug the same path is printed from C# and C++, but running the code in Release results in the PATH printed from c++ missing the D:\Temp folder
User Environment variables are per-process and changes are not propagated to other processes.
To change system environment variables in your example PATH. You need to modify the value under the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment and then broadcast a WM_SETTINGCHANGE message. Applications wishing to see the change will have to handle the broadcast.
Source: https://learn.microsoft.com/en-us/windows/win32/procthread/environment-variables
It turns out Windows provide more functions to get environment variables.
From the documentation "getenv and _putenv use the copy of the environment pointed to by the global variable _environ to access the environment." whereas GetEnvironmentVariable "Retrieves the contents of the specified variable from the environment block of the calling process."
From these statements GetEnvironmentVariable looks like the safest alternative and replacing getenv with GetEnvironmentVariable indeed resolve the problem.
References:
https://social.msdn.microsoft.com/Forums/en-US/c27a6623-6f57-4c7e-be9b-6dd35d362872/sharing-environment-variables-across-languages?forum=windowsgeneraldevelopmentissues
https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/getenv-wgetenv?view=vs-2019
https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getenvironmentvariable
Above is my folder structure. I have a Cordova app and a Windows Runtime Component - IBscanUltimate. The include folder has the C# code calling into the unmanaged IBscanUltimate.dll. Class1.cs is like this:
using System;
namespace IBscanUltimate
{
public sealed class Class1
{
public static String getSDK()
{
IBscanUltimate.DLL.IBSU_SdkVersion a = new DLL.IBSU_SdkVersion();
IBscanUltimate.DLL._IBSU_GetSDKVersion(ref a);
return "SDKVersion: " + a;
}
}
The IBScanUltimateApi.cs & _IBSU_GetSDKVersion look something like this:
internal partial class DLL
{
[DllImport("IBScanUltimate.DLL")]
private static extern int IBSU_GetSDKVersion(ref IBSU_SdkVersion pVerinfo);
public static int _IBSU_GetSDKVersion(ref IBSU_SdkVersion pVerinfo)
{
int nRc = IBSU_STATUS_OK;
nRc = IBSU_GetSDKVersion(ref pVerinfo);
return nRc;
}
}
I have placed the DLL in many locations to see if it'll get picked up and they all have the above properties. But when I try to run my app, it says unable to locate the IBScanUltimate.DLL
This is how the output is coming:
I am not sure what is it that I am doing wrong and why the DLLImport cannot find my dll. Thank you for your help.
Exact error is:
System.DllNotFoundException: Unable to load DLL 'IBScanUltimate.DLL': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
Update #1:
I have come across https://msdn.microsoft.com/en-us/library/windows/desktop/hh447159(v=vs.85).aspx This article is explaining that LoadPackagedLibrary function can be used to load the dll. I am not seeing any example on how to use this in C#.
Update #2:
Specify the search path for DllImport in .NET Mentions that SetDllDirectory or AddDllDirectory can be used. He has a code snippet for SetDllDirectory, but the argument is string[] paths. How would I specify the relative argument?
Update #3:
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool SetDllDirectory(string lpPathName);
public static bool setPath(String path)
{
//Windows.Storage.
//return SetDllDirectory("ms-appx:///");
return SetDllDirectory(path);
}
I tried calling the SetDllDirectory(path) method with various locations that my app should have access to but I am keep getting "false". Few examples that I have tried:
NativeMethods.setPath(Package.Current.InstalledLocation.Path.ToString());
StorageFolder localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
StorageFolder folder = Windows.Storage.KnownFolders.MusicLibrary;
This is where my app is installed:
C:\Users\AAA\App\hello\platforms\windows\build\windows\Debug\x64\AppX
and I can see that my DLL is there. But still I'm getting the exception that DLL cannot be found. Do I have to put something on the manifest regarding this?
Update #4:
I ran a dumpbin on the DLL and i see the below DLL in the dumpbin:
WINUSB.DLL
mfc90.dll
MSVCR90.dll
KERNEL32.dll
USER32.dll
GDI32.dll
VERSION.dll
MSVCP90.dll
SETUPAPI.dll
I guess I'd like to check on each dll above separately to see if my windows runtime can pick it? One of them could be the culprit that's not being loaded?
Update #5:
Upon seeing the answer from Peter Torr - MSFT, and googling for MFC I came across this article https://msdn.microsoft.com/en-us/library/d06h2x6e.aspx Which states:
The MFC classes and their members cannot be used in applications that execute in the Windows Runtime.
I guess to conclude this wild hunt now. I would close this up that the library I tried to load is dependent on libraries not available for Windows Runtime.
I had this feeling because Windows form application would run but the the code converted to Windows Runtime would give the error that the DLL is not being found. Thanks to Peter for guiding in the right direction.
The DLL you are trying to load was clearly built for desktop apps (it has User, GDI, and MFC imports) and will not work as a UWP binary. I suspect also that the DLL does not have the AppContainer flag set (an option you pass to the linker). You will need to find another way to accomplish what you need (if necessary, please make any feature requests via the Windows Platform UserVoice.
I suspect that it can find your DLL just fine, but it fails to find one or more of its dependencies. Unfortunately, both of these cases result in extremely generic DllNotFoundException that mentions the DLL your try to P/Invoke to.
There is an easy way to figure out what's missing! Windows contains a feature called "loader snaps", which, when enabled, will log all the things that Windows DLL loader does for your process. That means it will also print what DLLs it fails to load. To enable it, run this in admin command prompt:
gflags.exe -i "<executableName>.exe" +sls
Where executable name is just the name of your executable without the folder. To see the output, you will also need to enable either native or mixed mode debugger. You can do that in your project properties debugging tab in Visual Studio.
You can read more about load snaps here:
https://blogs.msdn.microsoft.com/junfeng/2006/11/20/debugging-loadlibrary-failures/
Consider the following solution structure: Windows Store C# application + 2 native libraries PInvokeServer and PInvokeServer1. Native libraries code:
// PInvokeServer1
PINVOKESERVER1_API int TestFunction1(void)
{
return 5;
}
// PInvokeServer
PINVOKESERVER_API int TestFunction(void)
{
return TestFunction1();
}
Both functions are extern C. PInvokeServer depends on PInvokeServer1 (using linker dependencies). PInvokeServer.dll and PInvokeServer1.dll are added to C# project with build action Content, so they are part of the application package. C# declarations:
const string dllName = #"Native\PInvokeServer.dll";
const string dllName1 = #"Native\PInvokeServer1.dll";
[System.Runtime.InteropServices.DllImport(dllName, CallingConvention = CallingConvention.Cdecl)]
public static extern int TestFunction();
[System.Runtime.InteropServices.DllImport(dllName1, CallingConvention = CallingConvention.Cdecl)]
public static extern int TestFunction1();
Case 1, doesn't work (module not found):
TestFunction();
Case 2, works:
TestFunction1();
Case 3, works:
TestFunction1();
TestFunction();
Case 1: When PInvoke tries to load PInvokeServer.dll, it cannot resolve native runtime dependency, PInvokeServer1.dll is not loaded, and I get Module not found exception. Placing PInvokeServer1.dll, for example, to System32 directory doesn't help.
Case 2: PInvoke is able to load PInvokeServer1.dll directly.
Case 3. Once PInvokeServer1.dll is loaded, PInvokeServer.dll can be loaded successfully as well.
Im my real program I have native C library depending on several other libraries. All these libraries are added to C# Store application package. But high-level library cannot be loaded, because PInvoke fails to load dependencies. The only way I can think about is to load low-level libraries using LoadLibrary PInvoke call, and finally use PInvoke call to high-level library. Is there better way?
In a desktop application you could use AddDllDirectory or SetDllDirectory to modify the search path. But in a Windows Store application these functions are not available to you. So I see two options:
Put the two DLLs in the same directory as the executable. This is, by some distance, the simplest and safest solution. The executable's directory is always the first location searched and so you can be sure that the right DLLs will be loaded.
Before calling any function in either DLL, call LoadLibrary passing the absolute path to the DLLs to load them into the process. Load PInvokeServer1 before PInvokeServer. Change your p/invoke declarations to specify just the DLL filename. That is, remove the Native directory from the p/invoke declaration. By calling LoadLibrary explicitly, you make sure that the two DLLs are loaded into the process. Then subsequent calls to p/invoke functions will result in the already loaded DLLs being used.
I getting bug: crash happened outside the Java Virtual Machine in native code. whenever i run with class file with native library and .net module file it works fine.
but when i try to run alone class file and native library it gets crash .please clarify my mistake i have done, please review my code.
for your reference with parameter
==========================================
public class Sum
{
public int add(int a, int b)
{
return a + b;
}
}
===========================================
save as Sum.cs and compile it to module
using cmd:
csc /t:module sum.cs
Create Java File to test
===========================================
public class test{
public native int add(int a,int b);
static {
System.loadLibrary("JSample");
}
public static void main (String[] args) {
System.out.println(new test().add(10,15));
}
}
==========================================
save it as test.java compile as
javac test.java
create native header file
javah -jni test
it will create test.h
create win32 project using visual studio (I used VS2010)
Choose project name as JSample
include header and C#.net module
write header for manged C++ conversion
==============================================
#using <mscorlib.dll>
#using "Sum.netmodule"
using namespace System;
public __gc class SumC
{
public:
Sum __gc *t;
SumC()
{
t = new Sum();
}
int callCSharpSum(int a,int b)
{
return t->add(a,b);
}
};
===========================================
save it as sum.h
create sum.cpp file
============================================
#include <jni.h>
#include "test.h"
#include "sum.h"
JNIEXPORT jint JNICALL Java_test_add
(JNIEnv *, jobject, jint a, jint b)
{
SumC* t = new SumC();
return t->callCSharpSum(a ,b );
}
=============================================
optimize compiler to build /clr:oldSyntax
Include Jdk/Include directory path
build the project.
we will Get JSample DLL
run the project
with C#.net module,Native DLL file and class file at the same folder.
java test
25
but whenever i run the code with dll file and class file alone.
it shows bug report The crash happened outside the Java Virtual Machine in native code.
please clarify how to port managed code C# into C++ (Win32 Un-Managed code). library file.
To use .NET assemblies from Java, I strongly suggest you look at IKVM, which is a Java VM that bridges to .NET Runtime.
I've used this back in (I think) 2004 for production software and it worked nicely. The project is actively maintained and recieves support for .NET 4 and Java 7 these days.
You have a choice of
running the Java code in IKVM so you can use .NET libraries
run a .NET program that loads java libraries (e.g. jars)
Both ways, there is a preprocessing step to translate the jars to DLLS or viceversa.
See http://ikvm.net