从C调用C＃ [英] Calling C from C#

问题描述

我是电气工程师的背景，因此我的知识是小的关于C＃，DLL，等....我想使用C函数到一个C＃。我知道有一对夫妇的帖子，但我没有找到一个是足够简单。

目前，我有C函数调用windows API读/写USB端口。首先创建一个.dll，我需要一个头文件吗？因为我得到了以下函数decleration函数到一个头。我在堆栈溢出和互联网上看到的例子只使用一个简单的.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 ReadUSBacket（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，我需要在cpp文件中编写__declspec（dllexport）吗？我们需要在cpp文件中编写__declspec（dllexport）。 这里是一个来自cpp的函数：
  externC__declspec（dllexport）BOOL PASCAL EXPORT TerminateDevice（LMUSB_HANDLE hUSB）
 
我不知道什么是BOOL PASCAL EXPORT，这个代码是从家具项目回收的。
 
 
 
 Finaly，当DLL被正确构建。如何在C＃项目中导入它？我尝试以下但未成功：
  [DllImport（lmusbdll.dll）] 
  
 
 
我看到你可以使用右键单击项目并添加引用，但Visual Studio弹出错误信息：
 无法添加对DLL路径的引用。请确保文件可访问，并且它是有效的程序集或COM组件。 
  
  
 
 
 
 解决方案，但是当我尝试引用头文件时在我的c＃项目。我仍然得到我不能引用该文件的消息。
解决方案
您不需要一个头文件，到__declspec（dllexport）的每个函数。如果是C ++（即.cpp文件），你需要externC。
 
 
 
有一个方便的程序，称为depends.exe， DLL，看看它导出什么函数，如果它取决于任何其他DLL。这可能是为什么你的DllImport失败。
 
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.

                        
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