使用c＃代码中的c ++ dll中定义的类

问题描述

我有一个用c ++编写的dll，我需要在我的c＃代码中使用这个dll。搜索后，我发现使用P / Invoke可以让我访问我需要的功能，但这些函数是在一个类中定义的，并使用非静态的私有成员变量。所以我需要能够创建这个类的一个实例来正确地使用这些功能。我如何获得访问这个类，以便我可以创建一个实例？我一直找不到这样做的办法。

我想我应该注意到c ++ dll不是我的代码。

解决方案>

没有办法直接在C＃代码中使用C ++类。您可以间接使用PInvoke来访问您的类型。

基本模式是对于Foo类中的每个成员函数，创建一个调用成员函数的关联非成员函数。

  class Foo {
 public：
 int Bar（）; 
}; 
 Foo * Foo_Create（）{return new Foo（）; } 
 int Foo_Bar（Foo * pFoo）{return pFoo-> Bar（）; } 
 void Foo_Delete（Foo * pFoo）{delete pFoo; } 
  

现在这是将这些方法插入到C＃代码中的一个问题

  [DllImport（Foo.dll）] 
 public static extern IntPtr Foo_Create（）; 
 
 [DllImport（Foo.dll）] 
 public static extern int Foo_Bar（IntPtr value）; 
 
 [DllImport（Foo.dll）] 
 public static extern void Foo_Delete（IntPtr value）; 
  

缺点是你会有一个尴尬的IntPtr传递，但创建一个简单的事情一个围绕这个指针的C＃包装类来创建一个更可用的模型。

即使你不拥有这个代码，你可以创建另一个DLL，它将原始的DLL和提供了一个小的PInvoke层。

I have a dll that was written in c++, I need to use this dll in my c# code. After searching I found that using P/Invoke would give me access to the function I need, but these functions are defined with in a class and use non-static private member variables. So I need to be able to create an instance of this class to properly use the functions. How can I gain access to this class so that I can create an instance? I have been unable to find a way to do this.

I guess I should note that the c++ dll is not my code.

解决方案

There is no way to directly use a C++ class in C# code. You can use PInvoke in an indirect fashion to access your type.

The basic pattern is that for every member function in class Foo, create an associated non-member function which calls into the member function.

class Foo {
public:
  int Bar();
};
Foo* Foo_Create() { return new Foo(); }
int Foo_Bar(Foo* pFoo) { return pFoo->Bar(); }
void Foo_Delete(Foo* pFoo) { delete pFoo; }

Now it's a matter of PInvoking these methods into your C# code

[DllImport("Foo.dll")]
public static extern IntPtr Foo_Create();

[DllImport("Foo.dll")]
public static extern int Foo_Bar(IntPtr value);

[DllImport("Foo.dll")]
public static extern void Foo_Delete(IntPtr value);

The downside is you'll have an awkward IntPtr to pass around but it's a somewhat simple matter to create a C# wrapper class around this pointer to create a more usable model.

Even if you don't own this code, you can create another DLL which wraps the original DLL and provides a small PInvoke layer.

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