C#调用C++ DLL 传出字符串，C++ DLL传参问题

C++ .h文件

VIDEO_DLL_API int __cdecl PlatformQueryRes(char* pcSvrIpAddress, char *pcLoginUserName, char** ppcResult);

C++ .cpp文件

int __cdecl PlatformQueryRes(char* pcSvrIpAddress, char *pcLoginUserName, char** ppcResult)
{
 if (!g_Global.m_bInitPlatformSDKFlag)
 {
  return Platform_ErrUnInit;
 }
 if (NULL == pcSvrIpAddress || NULL == pcLoginUserName || NULL == ppcResult)
 {
  return Platform_ErrInvalidParam;
 }
 string sResult;
 PlatformBase_ptr ptrPlatformBase = g_Global.GetPlatformObject(pcSvrIpAddress);
 if (ptrPlatformBase.get())
 {
  int iResult;
  iResult = ptrPlatformBase->QueryRes(pcLoginUserName, sResult); 
  if (iResult == Platform_ErrSuccess)
  {
   strcpy(*ppcResult, (char*)sResult.c_str());  
  }
  if (iResult == Platform_ErrQueryFail)
  {
   strcpy(*ppcResult, ""); 
  }
  return iResult;
 }else
 {
  return Platform_ErrQueryFail;
 }
}

C# .cs文件

public extern static int PlatformQueryRes(byte[] pcSvrIpAddress, byte[] pcLoginUserName, ref StringBuilder ppcResult);  

ref StringBuilder与char**相对应。

C#调用C++ DLL 传出字符串时，C++ DLL相应接口的传出字符串参数为char**。