从C＃调用C ++函数 [英] Calling C++ function from C#

问题描述

我有以下C ++函数

void FillAndReturnString(char ** someString)
{
   char sourceString[] = "test";
   *someString = new char[5];
   memcpy(*someString, sourceString, 5);   
}

它被声明为

extern "C"
{
__declspec(dllexport) void __cdecl FillAndReturnString(char ** someString);
}

如何从C＃调用此函数？

How do I call this function from C#?

感谢

推荐答案

您需要知道您在c ++函数中分配非托管内存块，因此不可能从C＃代码中传递受管字符串或数组对象以保持char数组。

You need to know that you're allocating unmanaged memory block in your c++ function, so it will not be possible to pass a managed String or Array object from C# code to 'hold' the char array.

一种方法是在您的本地dll中定义删除函数，并调用它来释放内存。在受管理方面，您可以使用 IntPtr 结构临时保存一个指向c ++ char数组的指针。

One approach is to define 'Delete' function in your native dll and call it to deallocate the memory. On the managed side, you can use IntPtr structure to temporarily hold a pointer to c++ char array.

// c++ function (modified)
void __cdecl FillAndReturnString(char ** someString)
{
   *someString = new char[5];
   strcpy_s(*someString, "test", 5);   // use safe strcpy
}

void __cdecl DeleteString(char* someString)
{
   delete[] someString
}


// c# class
using System;
using System.Runtime.InteropServices;

namespace Example
{
   public static class PInvoke
   {
      [DllImport("YourDllName.dll")]
      static extern public void FillAndReturnString(ref IntPtr ptr);

      [DllImport("YourDllName.dll")]
      static extern public void DeleteString(IntPtr ptr);
   }

   class Program
   {
      static void Main(string[] args)
      {
         IntPtr ptr = IntPtr.Zero;
         PInvoke.FillAndReturnString(ref ptr);

         String s = Marshal.PtrToStringAnsi(ptr);

         Console.WriteLine(s);

         PInvoke.Delete(ptr);
      }
   }

}

这篇关于从C＃调用C ++函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！