AddHandler / RemoveHandler处理不正确 [英] AddHandler/RemoveHandler Not Disposing Correctly

问题描述

使用 AddHandler 方法，如果我从不使用 RemoveHandler ，在某些情况下会导致内存泄漏，并且情况？我不太确定这是真的。

Using the AddHandler method, if I never use RemoveHandler, will that lead to memory leaks in some conditions and situations? I'm not so sure about the truth of this.

还有其他导致内存泄漏的原因，而这些原因仅在VB中才有，而不是C＃？

And are there other causes to memory leaks that are solely available in VB as opposed to C#?

推荐答案

通常不会。但是可能存在。

订阅事件，您基本上可以将方法的委托（如果有的话，可以使用func指针）提供给事件发布者，只要您不使用-=运算符取消订阅，该事件发布者就会保留该事件。

Well usually it doesn't.. but the possibility exists.
When you subscribe to an event, you basically give a delegate (a func pointer if you will) to your method to the event publisher, who holds on to it as long as you do not unsubscribe with the -= operator.

例如，生成一个子窗体，该窗体订阅了窗体上的Click按钮事件。

So take for example, the case where you spawn a child form and the form subscribes to the Click button event on the form.

button1.Click += new EventHandler(Form_Click_Handler);

现在，按钮对象将保留在窗体引用上。当窗体关闭/处置/设置为null不再需要form和button；内存被回收。

Now the button object will hold on to the form reference.. When the form is closed/disposed/set to null both form and button are not needed anymore; memory is reclaimed.

当您拥有寿命更长的全局结构或对象时，就会发生麻烦。可以说Application对象维护着一个打开的子窗口的列表。因此，无论何时创建子窗体，应用程序对象都会订阅Form事件，以便可以在其上保留选项卡。在这种情况下，即使关闭/放置了表单，应用程序对象也会保持活动状态（非垃圾对象会保留对表单的引用），并且不允许回收其内存。当您继续创建和关闭窗口时，您的应用会占用越来越多的内存，从而导致泄漏。因此，您需要明确地取消订阅，以从应用程序中删除表单引用。

The trouble happens when you have a global structure or object which has a bigger lifetime. Lets say the Application object maintains a list of open child windows. So whenever a child form is created, the application object subscribes to a Form event so that it can keep tabs on it. In this case, even when the form is closed/disposed the application object keeps it alive (a non-garbage object holds a ref to the form) and doesn't allow its memory to be reclaimed. As you keep creating and closing windows, you have a leak with your app hogging more and more memory. Hence you need to explicitly unsubscribe to remove the form reference from the application.

childForm.Event -= new EventHandler(Form_Handler)

因此，建议您使用一个取消订阅块（-=）来补充您的订阅例程（+ =）...但是在股票情况下，您可以不用它。

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