C#下System::String转换成C++下string

最近开发的C++项目中需要调用外部C#写的DLL驱动，网上有许多教程，可参考我前面转载的一篇blog。

程序调用成功后需要进行数据的转换，通过查找MSDN文档找到可调用Marshal类来实现。其中System::String转换成standed string可用StringToHGlobalAnsi，stand string转换成System::String可用PtrToStringAnsi附列，

// convert_system_string.cpp  
// compile with: /clr  
#include   
#include   
using namespace std;  
using namespace System;  
  
void MarshalString ( String ^ s, string& os ) {  
   using namespace Runtime::InteropServices;  
   const char* chars =   
      (const char*)(Marshal::StringToHGlobalAnsi(s)).ToPointer();  
   os = chars;  
   Marshal::FreeHGlobal(IntPtr((void*)chars));  
}  
  
void MarshalString ( String ^ s, wstring& os ) {  
   using namespace Runtime::InteropServices;  
   const wchar_t* chars =   
      (const wchar_t*)(Marshal::StringToHGlobalUni(s)).ToPointer();  
   os = chars;  
   Marshal::FreeHGlobal(IntPtr((void*)chars));  
}  
  
int main() {  
   string a = "test";  
   wstring b = L"test2";  
   String ^ c = gcnew String("abcd");  
  
   cout << a << endl;  
   MarshalString(c, a);  
   c = "efgh";  
   MarshalString(c, b);  
   cout << a << endl;  
   wcout << b << endl;  
}