Invoke 调用中的匿名方法 [英] Anonymous method in Invoke call

问题描述

在我们想在 Control.Invoke 中匿名调用委托的语法上有一些问题.

Having a bit of trouble with the syntax where we want to call a delegate anonymously within a Control.Invoke.

我们尝试了许多不同的方法，但都无济于事.

We have tried a number of different approaches, all to no avail.

例如:

myControl.Invoke(delegate() { MyMethod(this, new MyEventArgs(someParameter)); }); 

其中 someParameter 是此方法的本地

where someParameter is local to this method

以上会导致编译错误:

无法将匿名方法转换为类型System.Delegate"，因为它不是委托类型

Cannot convert anonymous method to type 'System.Delegate' because it is not a delegate type

推荐答案

因为 Invoke/BeginInvoke 接受 Delegate(而不是类型化的委托))，你需要告诉编译器创建什么类型的委托；MethodInvoker (2.0) 或 Action (3.5) 是常见的选择(注意它们有相同的签名)；像这样:

Because Invoke/BeginInvoke accepts Delegate (rather than a typed delegate), you need to tell the compiler what type of delegate to create ; MethodInvoker (2.0) or Action (3.5) are common choices (note they have the same signature); like so:

control.Invoke((MethodInvoker) delegate {this.Text = "Hi";});

如果需要传入参数，那么捕获的变量"是这样的:

If you need to pass in parameters, then "captured variables" are the way:

string message = "Hi";
control.Invoke((MethodInvoker) delegate {this.Text = message;});

(警告:如果使用捕获async，你需要有点谨慎，但sync 很好 - 即上面的很好)

(caveat: you need to be a bit cautious if using captures async, but sync is fine - i.e. the above is fine)

另一种选择是编写扩展方法:

Another option is to write an extension method:

public static void Invoke(this Control control, Action action)
{
    control.Invoke((Delegate)action);
}

然后:

this.Invoke(delegate { this.Text = "hi"; });
// or since we are using C# 3.0
this.Invoke(() => { this.Text = "hi"; });

你当然可以用 BeginInvoke 做同样的事情:

You can of course do the same with BeginInvoke:

public static void BeginInvoke(this Control control, Action action)
{
    control.BeginInvoke((Delegate)action);
}

如果您不能使用 C# 3.0，您可以使用常规实例方法执行相同的操作，大概在 Form 基类中.

If you can't use C# 3.0, you could do the same with a regular instance method, presumably in a Form base-class.

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