C# Invoke 调用中的匿名方法
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/253138/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Anonymous method in Invoke call
提问by Duncan
Having a bit of trouble with the syntax where we want to call a delegate anonymously within a Control.Invoke.
我们想在 Control.Invoke 中匿名调用委托的语法有点麻烦。
We have tried a number of different approaches, all to no avail.
我们尝试了许多不同的方法，但都无济于事。
For example:
例如：
myControl.Invoke(delegate() { MyMethod(this, new MyEventArgs(someParameter)); });
where someParameter is local to this method
其中 someParameter 是此方法的本地参数
The above will result in a compiler error:
以上将导致编译器错误：
Cannot convert anonymous method to type 'System.Delegate' because it is not a delegate type
无法将匿名方法转换为类型“System.Delegate”，因为它不是委托类型
采纳答案by Marc Gravell
Because Invoke/BeginInvokeaccepts 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:
因为Invoke/BeginInvoke接受Delegate（而不是类型化委托），您需要告诉编译器要创建什么类型的委托；MethodInvoker(2.0) 或Action(3.5) 是常见的选择（注意它们具有相同的签名）；像这样：
control.Invoke((MethodInvoker) delegate {this.Text = "Hi";});
If you need to pass in parameters, then "captured variables" are the way:
如果需要传入参数，那么“捕获的变量”是这样的：
string message = "Hi";
control.Invoke((MethodInvoker) delegate {this.Text = message;});
(caveat: you need to be a bit cautious if using captures async, but syncis fine - i.e. the above is fine)
（警告：如果使用捕获async，你需要有点谨慎，但同步很好 - 即上面的很好）
Another option is to write an extension method:
另一种选择是编写扩展方法：
public static void Invoke(this Control control, Action action)
{
control.Invoke((Delegate)action);
}
then:
然后：
this.Invoke(delegate { this.Text = "hi"; });
// or since we are using C# 3.0
this.Invoke(() => { this.Text = "hi"; });
You can of course do the same with BeginInvoke:
你当然可以做同样的事情BeginInvoke：
public static void BeginInvoke(this Control control, Action action)
{
control.BeginInvoke((Delegate)action);
}
If you can't use C# 3.0, you could do the same with a regular instance method, presumably in a Formbase-class.
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，大概是在Form基类中。
回答by Fran?ois
myControl.Invoke(new MethodInvoker(delegate() {...}))
回答by Jelon
You need to create a delegate type. The keyword 'delegate' in the anonymous method creation is a bit misleading. You are not creating an anonymous delegate but an anonymous method. The method you created can be used in a delegate. Like this:
您需要创建一个委托类型。匿名方法创建中的关键字“delegate”有点误导。您不是在创建匿名委托，而是在创建匿名方法。您创建的方法可以在委托中使用。像这样：
myControl.Invoke(new MethodInvoker(delegate() { (MyMethod(this, new MyEventArgs(someParameter)); }));
回答by Vokinneberg
Actually you do not need to use delegate keyword. Just pass lambda as parameter:
实际上您不需要使用委托关键字。只需将 lambda 作为参数传递：
control.Invoke((MethodInvoker)(() => {this.Text = "Hi"; }));
回答by Rory
I had problems with the other suggestions because I want to sometimes return values from my methods. If you try to use MethodInvoker with return values it doesn't seem to like it. So the solution I use is like this (very happy to hear a way to make this more succinct - I'm using c#.net 2.0):
我对其他建议有问题，因为我有时想从我的方法中返回值。如果您尝试将 MethodInvoker 与返回值一起使用，它似乎并不喜欢它。所以我使用的解决方案是这样的（很高兴听到一种更简洁的方法 - 我使用的是 c#.net 2.0）：
// Create delegates for the different return types needed.
private delegate void VoidDelegate();
private delegate Boolean ReturnBooleanDelegate();
private delegate Hashtable ReturnHashtableDelegate();
// Now use the delegates and the delegate() keyword to create
// an anonymous method as required
// Here a case where there's no value returned:
public void SetTitle(string title)
{
myWindow.Invoke(new VoidDelegate(delegate()
{
myWindow.Text = title;
}));
}
// Here's an example of a value being returned
public Hashtable CurrentlyLoadedDocs()
{
return (Hashtable)myWindow.Invoke(new ReturnHashtableDelegate(delegate()
{
return myWindow.CurrentlyLoadedDocs;
}));
}
回答by mhamrah
For the sake of completeness, this can also be accomplished via an Action method/anonymous method combination:
为了完整起见，这也可以通过 Action 方法/匿名方法组合来完成：
//Process is a method, invoked as a method group
Dispatcher.Current.BeginInvoke((Action) Process);
//or use an anonymous method
Dispatcher.Current.BeginInvoke((Action)delegate => {
SomeFunc();
SomeOtherFunc();
});
回答by Jürgen Steinblock
I never understood why this makes a difference for the compiler, but this is sufficient.
我从来不明白为什么这会对编译器产生影响，但这已经足够了。
public static class ControlExtensions
{
public static void Invoke(this Control control, Action action)
{
control.Invoke(action);
}
}
Bonus: add some error handling, because it is likely that, if you are using Control.Invokefrom a background thread you are updating the text / progress / enabled state of a control and don't care if the control is already disposed.
奖励：添加一些错误处理，因为很可能，如果您Control.Invoke从后台线程使用，您正在更新控件的文本/进度/启用状态，并且不关心该控件是否已被释放。
public static class ControlExtensions
{
public static void Invoke(this Control control, Action action)
{
try
{
if (!control.IsDisposed) control.Invoke(action);
}
catch (ObjectDisposedException) { }
}
}
回答by Du D.
I like to use Action in place of MethodInvoker, it is shorter and looks cleaner.
我喜欢用 Action 代替 MethodInvoker，它更短而且看起来更干净。
Invoke((Action)(() => {
DoSomething();
}));
// OR
Invoke((Action)delegate {
DoSomething();
});
Eg.
例如。
// Thread-safe update on a form control
public void DisplayResult(string text){
if (txtResult.InvokeRequired){
txtResult.Invoke((Action)delegate {
DisplayResult(text);
});
return;
}
txtResult.Text += text + "\r\n";
}
