具有C结构的C＃Pinvoke包含函数指针

Question

I struggled this for a while, still not able to figured out how to write code in C# side

C++ DLL

typedef void (WINAPI *P_HelloWorld)(void);
typedef struct {

P_HelloWorld pHelloWorld;

}FUNC_PARAM;

void Func4(FUNC_PARAM* pFunc)
{
   pFunc.pHelloWorld();
}

C# Side:

public delegate void P_HelloWord();
[StructLayout(LayoutKind.Sequential)]
public struct FUNC_PARAM
 {
   public P_HelloWord pHelloWorld;
 }

  [DllImport("EMV_DLL.dll")]

  public extern static void Func4(FUNC_PARAM[] pFunc);

 void main()
 {
   FUNC_PARAM g;
   g.pHelloWorld = new P_HelloWord(this.myHelloWorld);
   Func4(new FUNC_PARAM[] { g });
  }

void myHelloWorld()
{
   MessageBox.Show("My Hello World");
}

The above C# code doesn't work, when execute Func4 function, it throws out of memory exception.

Anybody could help me?

Answer 1

You don't appear to have posted the real code since the code in your question does not compile. Anyway, the following does work.

C++

typedef void (WINAPI *P_HelloWorld)(void);

typedef struct {
    P_HelloWorld pHelloWorld;
} FUNC_PARAM;

void Func4(FUNC_PARAM* pFunc)
{
   pFunc->pHelloWorld();
}

C#

public delegate void P_HelloWord();

public struct FUNC_PARAM
{
    public P_HelloWord pHelloWorld;
}

[DllImport(@"MyDll.dll", CallingConvention = CallingConvention.Cdecl)]
public extern static void Func4(ref FUNC_PARAM pFunc);

static void Main(string[] args)
{
    FUNC_PARAM pFunc;
    pFunc.pHelloWorld = myHelloWorld;
    Func4(ref pFunc);
    Console.ReadLine();
}

static void myHelloWorld()
{
    Console.WriteLine("Boo!");
}

Some points:

1. The parameter to Func4 is not an array. It's the address of the struct. So that makes it ref in C#.
2. The calling convention for Func4 is cdecl .
3. The implementation of Func4 does not compile in your code. I fixed it in mine.
4. Your C# main function was incorrect. It has to be a function declared as per my code.

---

Apparently you are using CE. There only is one calling convention there, stdcall. As for the error you report in the comments, stop wrapping the delegate in a struct and pass it directly.