C#调用 C++的 dll 动态链接库

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本文通过实例介绍如何在 c#中调用 C++编写的 dll。

1 首先用 C++编写一个测试用的 dll

1.1 新建一个 Win32 控制台工程

Drawing

1.2 Application settings 中将应用类型设置为 DLL

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1.3 在.cpp 文件中输入代码

#include "stdafx.h"
#include <stdio.h>
#include <string>
using namespace std;

extern "C"
{
  struct foo{
    int var1;
    int var2;
    unsigned char s[32];
    unsigned char r[32];
    double var3;
    char arr[16];
  };

  __declspec(dllexport)  int __stdcall DisplayHelloFromDLL(){
    printf("Hello from DLL\n");
    return 12345;
  }

  __declspec(dllexport) void __stdcall OutputStructValues(foo f){
    printf("\nEntering OutputStruct\n");
    printf("Size of struct is %d\n", sizeof(foo));
    printf("var1 = %d\n", f.var1);
    printf("var2 = %d\n", f.var2);
    printf("%s\n", f.s);
    printf("%s\n", f.r);
    printf("var2 = %10f\n", f.var3);
    printf("arr = %s\n", f.arr[2]);
    printf("Exiting OutputStruct\n\n");
  }

  __declspec(dllexport) void __stdcall TestArrayInOut(int * in, int * out, int nSize) {
    printf("\nEntering Array In out\n");
    for (int i = 0; i < nSize; i++)
    {
      //*(out + i) = *(in + i);//这样写竟然不行!在 c#中调用出错了
      out[i] = in[i] * 10;
    }
  }

关键的语句是：extern "C" __declspec(dllexport) void __stdcall

如果没有 __stdcall, 程序依然可以执行，但是调试时会报错。

2 C#中新建控制台程序，对 dll 进行测试

2.1 C#代码

using System;
using System.Runtime.InteropServices;

namespace cpp_dll_link
{
    unsafe class Program
    {
	[DllImport("DllTest.dll")]
	public static extern void DisplayHelloFromDLL();

	[DllImport("DllTest.dll")]
	public static extern void OutputStructValues(foo f);

	[DllImport("DllTest.dll")]
	public static extern void TestArrayInOut(IntPtr pin,IntPtr pout, int nSize);

	[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
	public struct foo
	{
	    public int inta;
	    public int intb;
	    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
	    public string z;
	    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
	    public string x;
	    public Double doub;
	    public fixed byte arr[16];
	}

	static void Main(string[] args)
	{
	    Console.WriteLine("This is C# program");
	    foo f;
	    f.inta = 10;
	    f.intb = 20;
	    f.z = "string1string1string1string1string1string1string1string1string1";
	    f.x = "string2";
	    f.doub = 5.67;
	    //f.arr = new byte[16];
	    for (int i = 0; i < 16; i++)
	    {
		f.arr[i] = (byte)(i + 97);
	    }
	    DisplayHelloFromDLL();

	    int[] a = { 0, 1, 2, 3 }; 
	    int[] b = { 0, 0, 0, 0 };
	    int size = Marshal.SizeOf(a[0]) * a.Length;
	    //Console.WriteLine("size: %d", size);
	    IntPtr pa = Marshal.AllocHGlobal(16);
	    IntPtr pb = Marshal.AllocHGlobal(16);
	    Marshal.Copy(a, 0, pa, 4);
	    Marshal.Copy(b, 0, pb, 4);
	    TestArrayInOut(pa, pb, 4);
	    for (int i = 0; i < 4; i++)
		Console.WriteLine(*((int *)pb + i));

	    OutputStructValues(f);
	    Console.WriteLine("End of app");
	    Console.ReadKey();
	}
    }
}

2.2 将 C++生成的 Dll 文件拷贝至 C#工程的调试目录下，然后就可以运行了

2.3 运行结果

Drawing

Date: <2016-09-22 四 17:30>

Author: ziyuan

Created: 2016-09-22 四 17:13

Emacs 25.1.50.1 (Org mode 8.2.10)

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