从 C# 程序访问 DLL 中的方法 [英] Access a method from a DLL from C# program

问题描述

我有一个 C 程序并且我创建了一个 DLL 文件.我使用的是 Windows Vista 和 Visual C++.

I have a C program and i have created a DLL file. I am using Windows Vista, and Visual C++.

现在我需要从 C# 代码的 Main() 方法访问该 DLL 中的方法.这样做的步骤是什么?

Now I need to access a method from that DLL, from the Main() method of a C# code. What are steps of doing so?

到目前为止我已经添加了DLL文件作为参考，之后我该怎么办?

So far I have added the DLL file as reference, thereafter what should I do?

这只是一个例子:

int main1( void ) {
  prinf("Hello World");
}

请注意，这个类也使我们可以使用其他 .lib 函数，但我能够成功地从中创建一个 DLL.(我不知道这是否相关)

Please note that this class also makes us of other .lib functions, but i was able to successfully create a DLL out of it. (I don't know if this is relevant)

现在我需要从我的 C# Main() 访问这个方法；

Now i need to access this method from my C# Main();

[STAThread]
static void Main()
{
  // I need to call that main1() method here

  Application.EnableVisualStyles();
  Application.SetCompatibleTextRenderingDefault(false);
  Application.Run(new Form1());
}

推荐答案

参见 使用在 c# 代码中的 c++ dll 中定义的类，这是一个很好的公认答案.正如 Hans Passant 在评论中所写，您不能添加本机 DLL 作为对 C# 项目的引用.

See using a class defined in a c++ dll in c# code which has a great accepted answer. And as Hans Passant wrote in the comments, you cannot add a native DLL as a reference to a C# project.

当我引用自己的本机 DLL 之一时，我通常要么在 C# 项目和生成本机 DLL 的项目之间添加依赖项，要么将 DLL 添加为 C# 项目中的链接内容文件，如下所示:

When I refer to one of my own native DLLs, I usually either add a dependency between the C# project and the project which generates the native DLL, or I add the DLL as a linked content file in the C# project, like so:

1. 右键单击该项目，然后选择添加">现有项目".
2. 浏览并选择您想要的 DLL，但先不要点击添加.
3. 点击添加按钮右侧的小箭头，然后选择添加为链接.
4. 选择现在出现在您的 C# 项目中的 DLL 并转到其属性.
5. 确保将构建操作设置为内容.

1. Right-click on the project and choose Add > Existing Item.
2. Browse and select the DLL you want, but don't click Add yet.
3. Click on the tiny arrow at the right of the Add button and select Add As Link.
4. Select the DLL that now appears in your C# project and go to its properties.
5. Make sure you have Build Action set to Content.

这会将 DLL 复制到 C# 项目的 binDebug 文件夹中，并确保一旦您决定创建一个安装项目，您就可以轻松引用所有内容文件 并将它们包含在 Microsoft 安装程序包中.

This will copy the DLL to the binDebug folder of the C# project and make sure that, if you once decide to create a Setup project, you can easily reference all content files and include them in the Microsoft Installer package.

现在，为了能够看到在您的本机 DLL 中编写的函数，您必须注意导出它们(请参阅 导出 C 函数以用于 C 或 C++ 语言可执行文件 和 使用 __declspec(dllexport) 从 DLL 导出).因此，您必须在函数声明周围添加一个 extern "C" 块(我假设您在 .cpp 源文件中编写了代码，这意味着如果您不将它们声明为 extern "C")，编译器将发出 mangled 函数名:

Now, to be able to see the functions written in your native DLL, you have to take care of exporting them (see Exporting C Functions for Use in C or C++ Language Executables and Exporting from a DLL Using __declspec(dllexport)). So you'd have to add an extern "C" block around your function declaration (I am assuming you wrote your code in a .cpp source file and this means that the compiler will emit mangled function names if you do not declare them as being extern "C"):

extern "C"
{
    __declspec (dllexport) void __cdecl Foo(const char* arg1);
}

...

void Foo(const char* arg1)
{
    printf ("Hello %s !", arg1);
}

__declspec (dllexport) 修饰意味着编译器/链接器必须使函数从 DLL 外部可见.而 __cdecl 定义了如何将参数传递给函数(标准的C"方式这样做).

The __declspec (dllexport) decoration means that the compiler/linker will have to make the function visible from outside of the DLL. And the __cdecl defines how parameters will be passed to the function (the standard "C" way of doing this).

在您的 C# 代码中，您必须引用 DLL 的导出方法:

In your C# code, you'll have to refer to your DLL's exported methods:

class Program
{
    [DllImport("mydll.dll")]
    internal static extern void Foo(string arg1);

    static void Main()
    {
        Program.Foo ("Pierre");
    }
}

您应该阅读平台调用教程 给出了所有血腥的细节.

You should read the Platform Invoke Tutorial which gives all the gory details.

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