C#CS0079事件处理编译错误 [英] C# CS0079 Event Handling Compile Errors

问题描述

我无法编译以下代码.

编译错误CS0079:"CustomEvent"事件只能出现在+ =或-=

if (CustomEvent != null)   //CS0079
    CustomEvent(null, null);  //CS0079

我该如何进行这项工作?

How can I make this work?

我的实现是这样的:

public delegate void EventHandler(object sender, EventArgs e);  
public static event EventHandler CustomEvent
{
    add    { CustomEvent += value; }
    remove { CustomEvent -= value; }
 }
private static void Func()
{
    if (CustomEvent != null)      //CS0079
        CustomEvent(null, null);  //CS0079
}

推荐答案

您的编辑显示了一个递归调用:您正在声明一个自定义事件，这意味着您旨在提供一个后备字段；例如:

Your edit shows a recursive call: you are declaring a custom event, which means you are meant to provide a backing field; for example:

private static EventHandler customEvent;
public static event EventHandler CustomEvent
{
    add    { customEvent += value; }
    remove { customEvent -= value; }
 }
private static void Func()
{
    var tmp = customEvent;
    if (tmp != null) tmp(null, null);
}

请注意，在 Func 中，我指的是 字段 ( customEvent )，而不是事件 ( CustomEvent ).

Note that in Func I am referring to the field (customEvent), not the event (CustomEvent).

但是，作为类似字段的事件，此方法更简单(线程安全)更好:

However, this is simpler are better (thread-safe) as a field-like event:

public static event EventHandler CustomEvent;
private static void Func()
{
    var tmp = CustomEvent;
    if (tmp != null) tmp(null, null);
}

类似字段的事件使用 event 关键字，但忽略访问器:编译器为您添加了很多样板(支持字段，并且线程安全添加/删除实现).此外，它允许通过事件名称(从声明类型)通过事件名称访问提交的后备文件，因此行 var tmp = CustomEvent; 的工作方式.

A field-like event uses the event keyword, but omits the accessors: the compiler adds a lot of boilerplate for you (a backing field, and thread-safe add/remove implementations). Further, it allows access to the backing filed via the event name (from the declaring type), hence how the line var tmp = CustomEvent; works.

也:对静态事件要非常小心；它们是意外保留许多物体的好方法.

Also: be very careful with static events; they are a great way to accidentally keep lots of objects alive.

这篇关于C#CS0079事件处理编译错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！