c#和c++数据交互二

class A
{
public:
	int a;	
};
typedef struct 
{
	   int up;
	  
	   int down;
	   char infos[4];
	//LPWSTR infos;
}info,*LPinfo;

#define CVAPI  extern "C"  __declspec(dllexport) 
CVAPI  int Add1(int a,int b ,int len);

对应c#
[DllImport(Dllpath, CallingConvention = CallingConvention.StdCall)] 
public static extern int Add1(int a,int b ,int len);

//定义函数模型
int _declspec(dllexport)_stdcall FuncCsharp(int*);
回调
int CallBackAdd(int a, intptr_t callBack)
{ 
    decltype(FuncCsharp)* callHander = NULL;
    if (callBack != 0)
    {
        callHander = (decltype(FuncCsharp)*)callBack;
    }
    int b = 6;
    if (callHander != NULL)
    {
         b = callHander(&a);
    }
    return b;
}

c#使用
   [DllImport(Dllpath, CallingConvention = CallingConvention.StdCall)]
   public static extern int CallBackAdd(int a, IntPtr strPtr);
 public delegate int CsharpCall(ref int a);
 CsharpCall c = new CsharpCall(CsharpMethod);
 IntPtr ptr = Marshal.GetFunctionPointerForDelegate(c);
 var p2 = ptr.ToPointer();
var val=CallBackAdd(5, ptr);

c#                                 c++
int,short,byte,long                int,short,byte,long
ref int,short,byte,long            int*,short*,byte*,long*
结构体c#里是托管类型，在封送时需要注意以下特性
  
   [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
   [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
 public static extern int StringToChar([MarshalAs(UnmanagedType.LPStr)] string str);