动作<>多参数语法说明 [英] Action<> multiple parameters syntax clarification

问题描述

有时候我听不懂最简单的东西，我确定它在我的脸上，只是看不到它。
我试图在此简单类中为方法创建委托：

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:

public static class BalloonTip
{
    public static BalloonType BalType
    { 
        get; 
        set; 
    }

    public static void ShowBalloon(string message, BalloonType bType)
    {
        // notify user
    }
}

现在，此Action<>应该创建委托而不实际使用关键字 delegate声明一个委托，我理解正确吗？然后：

Now, this Action<> is supposed to create the delegate without actually declaring one with the keyword "delegate", did I understand correctly? Then:

private void NotifyUser(string message, BalloonTip.BalloonType ballType)
    {
        Action<string, BalloonTip.BalloonType> act; 
        act((message, ballType) => BalloonTip.ShowBalloon(message,  ballType));
    }

此操作无法编译。为什么？

This fails to compile. Why?

（顺便说一句，我之所以需要此委托而不是直接调用ShowBalloon（）的原因是，这些调用必须从不同于UI的另一个线程进行，所以我想我需要Action<>）

(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<>)

谢谢

推荐答案

您需要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：

You need to first assign your anonymous method to the Action variable, then invoke it with the arguments passed in to the method:

private void NotifyUser(string message, BalloonTip.BalloonType ballType)
{
    Action<string, BalloonTip.BalloonType> act = 
        (m, b) => BalloonTip.ShowBalloon(m, b);

    act(message, ballType);
}

在这种情况下，由于您的期望的参数操作变量与封装方法的变量相同，您也可以直接引用该方法：

In this case, since the arguments expected by your Action variable are identical to those of the encapsulated method, you may also reference the method directly:

private void NotifyUser(string message, BalloonTip.BalloonType ballType)
{
    Action<string, BalloonTip.BalloonType> act = BalloonTip.ShowBalloon;

    act(message, ballType);
}

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