从C＃调用C [英] Calling C from C#

问题描述

我来自电气工程师的背景，所以我知道C＃，DLL等等。我想使用c函数到C＃。我知道有一个关于这个的几个帖子，但我没有找到一个足够简单的。

目前，我有C函数调用Windows API来读/写USB端口。首先要创建一个.dll，我需要一个头文件吗？因为我得到以下函数decleration函数到一个标题。我在堆栈溢出和互联网上看到的示例只使用一个简单的.c文件，我可以摆脱头文件吗？

  __ declspec（dllexport）LMUSB_HANDLE __stdcall InitializeDevice（unsigned short usVID，
 unsigned short usPID，
 LPGUID lpGUID，
 BOOL * pbDriverInstalled）; 
 __declspec（dllexport）LMUSB_HANDLE __stdcall InitializeDeviceByIndex（unsigned short usVID，
 unsigned short usPID，
 LPGUID lpGUID，
 DWORD dwIndex，
 BOOL bOpenDataEndpoints，
 BOOL * pbDriverInstalled）; 
 __declspec（dllexport）BOOL __stdcall TerminateDevice（LMUSB_HANDLE hHandle）; 
 __declspec（dllexport）BOOL __stdcall WriteUSBPacket（LMUSB_HANDLE hHandle，
 unsigned char * pcBuffer，
 unsigned long ulSize，
 unsigned long * pulWritten）; 
 __declspec（dllexport）DWORD __stdcall ReadUSBPacket（LMUSB_HANDLE hHandle，
 unsigned char * pcBuffer，
 unsigned long ulSize，
 unsigned long * pulRead，
 unsigned long ulTimeoutMs，
 HANDLE hBreak）; 
 __declspec（dllexport）BOOL __stdcall Endpoint0Transfer（LMUSB_HANDLE hHandle，UCHAR ucRequestType，
 UCHAR ucRequest，USHORT usValue，
 USHORT usIndex，USHORT usLength，
 PUCHAR pucBuffer，PUSHORT pusCount）; 
  

第二点，需要在cpp文件中写__declspec（dllexport）吗？这里有一个来自cpp的函数：

  externC__declspec（dllexport）BOOL PASCAL EXPORT TerminateDevice（LMUSB_HANDLE hUSB）
  

我不知道BOOL PASCAL EXPORT是什么，这段代码是从家具项目中回收的。 >

最终，当DLL正确构建时。我如何在C＃项目中导入它？我试过以下但没有成功：

  [DllImport（lmusbdll.dll）] 
  

我看到您可以使用右键单击项目并添加引用，但Visual Studio弹出错误消息：

 无法添加对DLL路径的引用。请确保该文件可访问，并且它是一个有效的程序集或COM组件。 
  

遵循解决方案，但是当我尝试引用头文件在我的c＃项目。我仍然收到我无法引用该文件的消息。

解决方案

您不需要头文件，但您将需要到__declspec（dllexport）每个函数。如果是C ++（即一个.cpp文件），你将需要externC。

有一个方便的程序，称为depends.exe，可以让你看看DLL并查看它导出的函数，如果它依赖于任何其他DLL。这可能是您的DllImport失败的原因。

I am from electric engineer background, therefore my knownledge is small about C#,DLL,etc.... I want to use c function into a C#. I know there is a couple post about that but I didn't find one that is enough simple.

Currently, I got C function call windows API to read/write on the USB port. First to create a .dll do I need a header file? Because I got the following function decleration function into a header. The examples that I saw on stack overflow and Internet only use a simple .c file, Can I get rid of the header files?

__declspec(dllexport) LMUSB_HANDLE  __stdcall InitializeDevice(unsigned short usVID,
                                    unsigned short usPID,
                                    LPGUID lpGUID,
                                    BOOL *pbDriverInstalled);
__declspec(dllexport) LMUSB_HANDLE  __stdcall InitializeDeviceByIndex(unsigned short usVID,
                                           unsigned short usPID,
                                           LPGUID lpGUID,
                                           DWORD dwIndex,
                                           BOOL bOpenDataEndpoints,
                                           BOOL *pbDriverInstalled);
__declspec(dllexport) BOOL  __stdcall TerminateDevice(LMUSB_HANDLE hHandle);
__declspec(dllexport) BOOL  __stdcall WriteUSBPacket(LMUSB_HANDLE hHandle,
                          unsigned char *pcBuffer,
                          unsigned long ulSize,
                          unsigned long *pulWritten);
__declspec(dllexport) DWORD  __stdcall ReadUSBPacket(LMUSB_HANDLE hHandle,
                         unsigned char *pcBuffer,
                         unsigned long ulSize,
                         unsigned long *pulRead,
                         unsigned long ulTimeoutMs,
                         HANDLE hBreak);
 __declspec(dllexport) BOOL  __stdcall Endpoint0Transfer(LMUSB_HANDLE hHandle, UCHAR ucRequestType,
                             UCHAR ucRequest, USHORT usValue,
                             USHORT usIndex, USHORT usLength,
                             PUCHAR pucBuffer, PUSHORT pusCount);

Second point, do I need to write __declspec(dllexport) in the cpp file? Here an function from the cpp:

extern "C" __declspec(dllexport) BOOL PASCAL EXPORT TerminateDevice(LMUSB_HANDLE hUSB)

I got no idea what "BOOL PASCAL EXPORT" does, this code is recycled from a furnisher project.

Finaly, when the DLL is properly build. How I import it in the C# project? I tried the following but without success :

[DllImport("lmusbdll.dll")]

I see that you could use right click on the project and add reference but Visual Studio pop-up an error message:

A reference to "DLL path" could not be added. Please make sure that the file is accessible, and that it is a valid assembly or COM component.

[EDIT]

I tried the following solution , but when I tried to reference the header file in my c# project. I still get the message that I cannot reference the file.

解决方案

You don't need a header file, but you will need to __declspec(dllexport) each function. And if it's C++ (i.e. a .cpp file) you'll need extern "C".

There's a handy program called depends.exe that allows you to look at a DLL and see what functions it exports and if it depends on any other DLLs. That might be why your DllImport is failing.

这篇关于从C＃调用C的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！