使用DLL将C# StringBuilder / string传递给C++ char*

using System;
using System.Runtime.InteropServices;
using System.Text;

namespace MyDll
{
    public class MyDllClass
    {
        [DllImport("MyCppDll.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern void MyCppFunction(IntPtr str);

        public static void PassStringToCpp(string str)
        {
            byte[] bytes = Encoding.ASCII.GetBytes(str);
            IntPtr ptr = Marshal.AllocHGlobal(bytes.Length + 1);
            Marshal.Copy(bytes, 0, ptr, bytes.Length);
            Marshal.WriteByte(ptr + bytes.Length, 0); // Null-terminate the string

            MyCppFunction(ptr);

            Marshal.FreeHGlobal(ptr);
        }
    }
}

#include <iostream>

extern "C" __declspec(dllexport) void MyCppFunction(char* str)
{
    std::cout << "Received string from C#: " << str << std::endl;
}

using System;
using MyDll;

class Program
{
    static void Main()
    {
        string myString = "Hello from C#!";
        MyDllClass.PassStringToCpp(myString);
    }
}