C# Action<> 多参数语法说明
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Action<> multiple parameters syntax clarification
提问by Amc_rtty
Sometimes I can't understand the simplest things, i'm sure it's in my face, i just fail to see it. Im trying to create a delegate for a method in this simple class:
有时我无法理解最简单的事情，我确信它在我的脸上，我只是看不到它。我试图在这个简单的类中为一个方法创建一个委托：
public static class BalloonTip
{
public static BalloonType BalType
{
get;
set;
}
public static void ShowBalloon(string message, BalloonType bType)
{
// notify user
}
}
Now, this Action<> is supposed to create the delegate without actually declaring one with the keyword "delegate", did I understand correctly? Then:
现在，这个 Action<> 应该创建委托而不用实际声明一个关键字“delegate”，我理解正确吗？然后：
private void NotifyUser(string message, BalloonTip.BalloonType ballType)
{
Action<string, BalloonTip.BalloonType> act;
act((message, ballType) => BalloonTip.ShowBalloon(message, ballType));
}
This fails to compile. Why?
这无法编译。为什么？
(By the way, the reason why I need this delegate instead of directly calling ShowBalloon(), is that the calls must be made from another thread than the UI one, so I figured I need the Action<>)
（顺便说一下，我需要这个委托而不是直接调用 ShowBalloon() 的原因是调用必须从另一个线程而不是 UI 线程进行，所以我想我需要 Action<>）
Thanks,
谢谢，
采纳答案by Douglas
You need to first assign your anonymous method to the Actionvariable, then invoke it with the arguments passed in to the method:
您需要首先将匿名方法分配给Action变量，然后使用传递给方法的参数调用它：
private void NotifyUser(string message, BalloonTip.BalloonType ballType)
{
Action<string, BalloonTip.BalloonType> act =
(m, b) => BalloonTip.ShowBalloon(m, b);
act(message, ballType);
}
In this case, since the arguments expected by your Actionvariable are identical to those of the encapsulated method, you may also reference the method directly:
在这种情况下，由于您的Action变量期望的参数与封装方法的参数相同，您也可以直接引用该方法：
private void NotifyUser(string message, BalloonTip.BalloonType ballType)
{
Action<string, BalloonTip.BalloonType> act = BalloonTip.ShowBalloon;
act(message, ballType);
}
回答by Marcelo Zabani
Shouldn't you assign to the actvariable? Something in the lines of:
你不应该分配给act变量吗？在以下方面的东西：
Action<string, BalloonTip.BalloonType> act = BalloonTip.ShowBalloon;
Not only did you not assign a method to act, as it seems you are trying to invoke act passing it a anonymous method as a parameter, while it receives a string and a BalloonTip.BalloonType.
In the end, you should return act, and thus your method to get a delegate to the notification method should be:
您不仅没有将方法分配给act，因为您似乎试图调用将匿名方法作为参数传递给它的行为，同时它接收一个字符串和一个 BalloonTip.BalloonType。
最后，您应该 return act，因此您获取通知方法委托的方法应该是：
public Action<string, BalloonTip.BalloonType> GetNotificationMethod() {
Action<string, BalloonTip.BalloonType> act = BalloonTip.ShowBalloon;
return act;
}
You can also make it simpler:
你也可以让它更简单：
public Action<string, BalloonTip.BalloonType> GetNotificationMethod() {
return BalloonTip.ShowBalloon;
}
Hope I understood your question ok. Good luck.
希望我能理解你的问题。祝你好运。
