C#调用C++的Dll(参数和返回值為char* TCHAR*)--Donnie2016，写的很好！转下

想要在C#和C++之间进行字符串传递会涉及到两件事情:

1.C#的string和C++的字符串首指针要怎么对应.  

2.字符串分为ANSI和UNICODE.

C++ 头文件接口:

 //FilePolice.h

 //參數和返回值為Ansi
 extern "C" __declspec(dllexport) char* __stdcall EncryptString(char* in_string);
 //參數和返回值為Unicode
 extern "C" __declspec(dllexport) TCHAR* __stdcall EncryptStringW(TCHAR* in_string);
 //參數和返回值為int
 extern "C" __declspec(dllexport) int __stdcall Sum(int a, int b);

C++ 实现部分:

 // FilePolice.cpp

 #include "stdafx.h"
 #include "FilePolice.h"

 TCHAR* __stdcall EncryptStringW(TCHAR* in_string)
 {
     return in_string;
 }

 char* __stdcall EncryptString(char* in_string)
 {
     return in_string;
 }

 int __stdcall Sum(int a, int b)
 {
     return a + b;
 }

C# 调用部分:

 class Program
 {
     [DllImport("FilePolice")]
     public static extern int Sum(int a, int b);

     ////[DllImport("FilePolice", CallingConvention = CallingConvention.Cdecl)]
     ////[DllImport("FilePolice", CallingConvention = CallingConvention.StdCall)]
     ////UnmanagedType.LPStr 為 ANSI
     ////UnmanagedType.LPWStr 為 Unicode
     [DllImport("FilePolice", CharSet = CharSet.Unicode)]
     public static extern IntPtr EncryptStringW([MarshalAs(UnmanagedType.LPWStr)]string inString);

     [DllImport("FilePolice", CharSet = CharSet.Ansi)]
     public static extern IntPtr EncryptString([MarshalAs(UnmanagedType.LPStr)]string inString);

     static void Main(string[] args)
     {
         int result = Sum(1, 2);
         Console.WriteLine(result.ToString());

         //Unicode
         IntPtr ip = EncryptStringW("Hello 您好.");
         string strIP = Marshal.PtrToStringUni(ip);
         Console.WriteLine(strIP);

         //Ansi
         ip = EncryptString("Hello 您好.");
         strIP = Marshal.PtrToStringAnsi(ip);
         Console.WriteLine(strIP);

         Console.ReadLine();
     }
 }

为了C#能方便调用,在C++中特别将调用方式设置为:__stdcall . (关于调用方式的详细说明,请进 传送门). 否则需要在C#里指定 [DllImport("FilePolice", CallingConvention = CallingConvention.Cdecl)].

另外,由于我们的字符串中会使用到中文,所以一般使用Unicode的方式进行传递.