C#调用dll 返回char *类型时

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;

namespace ConsoleApp3
{
    class Program
    {
        [DllImport(@"C:\Users\cj\source\repos\ConsoleApp3\ConsoleApp3\BDK01ForCryptolDll.dll")]
        public static extern bool OpenBDK01();
        [DllImport(@"C:\Users\cj\source\repos\ConsoleApp3\ConsoleApp3\BDK01ForCryptolDll.dll")]
        public static extern bool CloseBDK01();
        [DllImport(@"C:\Users\cj\source\repos\ConsoleApp3\ConsoleApp3\BDK01ForCryptolDll.dll")]
        public static extern int GetMyPinCount();
        [DllImport(@"C:\Users\cj\source\repos\ConsoleApp3\ConsoleApp3\BDK01ForCryptolDll.dll")]
        public static extern IntPtr GetDevSN();
        [DllImport(@"C:\Users\cj\source\repos\ConsoleApp3\ConsoleApp3\BDK01ForCryptolDll.dll")]
        public static extern char LoginForBDK01(Byte[] lpPassword, int iPWLen);
        [DllImport(@"C:\Users\cj\source\repos\ConsoleApp3\ConsoleApp3\BDK01ForCryptolDll.dll")]
        public static extern char EncryptForSM4(byte[] lpEData, byte[] lpDData, int iDLen);
        [DllImport(@"C:\Users\cj\source\repos\ConsoleApp3\ConsoleApp3\BDK01ForCryptolDll.dll")]
        public static extern char DecyptForSM4(byte[] lpDData, byte[] lpEData, int iDLen);
        static void Main(string[] args)
        {
            bool Device_status = OpenBDK01();
            string devsn = Marshal.PtrToStringAnsi(GetDevSN());

            while (true)
            {
                Console.WriteLine("the device SN is {0}", devsn);
                Console.WriteLine("the device status is {0}", Device_status);

            }
        }
    }
}

一、IntPtr 与 string互转

string str = "aa";

IntPtr init = Marshal.StringToHGlobalAnsi(str);

string ss= Marshal.PtrToStringAnsi(init);

//最后释放掉

Marshal.FreeHGlobal(init);

二、char*与string互转

string a = "11";

char* aChar = (char*)System.Runtime.InteropServices.Marshal.StringToHGlobalAnsi(a).ToPointer();

string result = Marshal.PtrToStringAnsi((IntPtr)aChar);

三、char* 与 IntPtr互转

可以直接强制类型转换

IntPtr init = (IntPtr)aChar;

char* aChar = (char*)init;