C#调用C++dll 传出字符串

//C++ 函数返回字符串
#include <iostream>
#include <string>
using namespace std;
//错误
const char* getStr1()
{
	string s = "1";
	return s.c_str();
}
//正确
string getStr2()
{
	string s = "1";
	return s;
}
//正确
const void getStr3(string &s)
{
	s = "1";
}
//正确
const void getStr4(char** s)
{
	strcpy(*s ,"1");
}
int main()
{
	const char* s1 = getStr1();
	cout<<s1<<endl;
	string s2 = getStr2();
	cout<<s2<<endl;
	string s3;
	getStr3(s3);
	cout<<s3<<endl;
	char* s4 = new char[10];
	getStr4(&s4);
	cout<<s4<<endl;
	return 0;
}

结果：

.h文件

extern "C" _declspec(dllexport) int _stdcall GetFileID(char** ptrStr,unsigned char* data,int dataLen);

.cpp文件