使用非托管导出将字符串从C#返回到C++将返回数字

extern "C" __declspec(dllexport) int GetStringFromCSharp(char* str)
{
    // 在这里处理字符串，并返回数字
    return 123;
}

using System;
using System.Runtime.InteropServices;

class Program
{
    [DllImport("YourCppLibrary.dll")]
    public static extern int GetStringFromCSharp(StringBuilder str);

    static void Main()
    {
        StringBuilder sb = new StringBuilder(256);
        int result = GetStringFromCSharp(sb);
        string returnedString = sb.ToString();

        Console.WriteLine("返回的数字：" + result);
        Console.WriteLine("从C++返回的字符串：" + returnedString);
    }
}