定义一个委托作为函数指针 [英] Defining a delegate as a function pointer

问题描述

我使用它调用非托管函数指针的委托。这将导致垃圾收集器收集它，使用它之前，作为MSDN的CallbackOnCollectedDelegate MDA页面描述：的为CallbackOnCollectedDelegate MDA 的MSDN页面。

这是我必须元帅适当的委托作为非托管函数指针的解决状态。我最初的反射是使用：

  [的MarshalAs（UnmanagedType.FunctionPtr）
公众委托无效EntityCallback（[的MarshalAs （UnmanagedType.SysInt）] IntPtr的实体）; 
  

不过，C＃编译器不会让我元帅代表，即使这是建议的解决方案通过MSDN。此外，MSDN页面只显示了问题的一个例子被抛出，但不是决议之一。

我怎么能元帅我的委托作为非托管函数指针或保留它被GCed

修改：作为建议，我创建了回调的参考。因此，我的代码改为从/到：

  //来源：
 foo.SetCallback（新EntityCallback（巴） ）; 
 
 //要：
调用=新EntityCallback（巴）; //引用类
 foo.SetCallback（电话）; 
  

现在这样做的工作 - 但只有在调试模式下。当我切换到发布，它崩溃在同一地点。 ？这是为什么

编辑2 ：更完整的代码片段：

 公共类测试
 {
私人EntityCallback呼叫; 
 
私人无效栏（System.IntPtr目标）
 {
：
} 
 
公共实体的Foo {搞定;组; } 
 
公开测试（）
 {
 this.Foo =新Body.Sphere（）{可见= FALSE}; //无关
 this.Foo.CollisionType = 3; //无关
 
 this.Call =新EntityCallback（this.Bar）; 
 
 this.Foo.SetCallback（this.Call，EntityCallbackType.Collision）; 
} 
} 
  

解决方案

您没有正确读取它。你必须这样做：

...更改您的代码，以保持一个参考
到委托的管理方
为封
非托管函数指针的寿命。

在换句话说，只储存到委托的引用比如在你的类，并确保类对象存活足够长的时间。使用静态，如果你真的不得不这样做。

I am using a delegate which calls an unmanaged function pointer. This causes the Garbage Collector to collect it before it is used, as described in the CallbackOnCollectedDelegate MDA page on MSDN: MSDN page for CallbackOnCollectedDelegate MDA.

The resolution states that I have to marshal the appropriate delegate as an unmanaged function pointer. My initial reflex was to use:

[MarshalAs(UnmanagedType.FunctionPtr)]
public delegate void EntityCallback([MarshalAs(UnmanagedType.SysInt)] IntPtr entity);

However, the C# compiler won't let me marshal a delegate, even if this is the suggested resolution by MSDN. Moreover, the MSDN page only shows an example of the problem being thrown, but not one of the resolution.

How could I marshal my delegate as an unmanaged function pointer or keep it from being GCed?

EDIT: As suggested, I created a reference of the callback. Therefore, my code changed from/to:

// From:
foo.SetCallback(new EntityCallback(bar));

// To:
call = new EntityCallback(bar); // Referenced in class
foo.SetCallback(call);

Now this does work - but only in Debug mode. When I switch to Release, it crashes at the same point. Why is that?

EDIT 2: More complete code snippet:

public class Test
{
    private EntityCallback Call;

    private void Bar(System.IntPtr target)
    {
        ...
    }

    public Entity Foo { get; set; }

    public Test()
    {
        this.Foo = new Body.Sphere() { Visible = false }; // Irrelevant
        this.Foo.CollisionType = 3; // Irrelevant

        this.Call = new EntityCallback(this.Bar);

        this.Foo.SetCallback(this.Call, EntityCallbackType.Collision);
    }
}

解决方案

You didn't read it correctly. You must do this:

...change your code to keep a reference to that delegate on the managed side for the lifetime of the marshaled unmanaged function pointer.

In other words, just store a reference to the delegate instance in your class and make sure the class object survives long enough. Use a static if you really have to.

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