问题描述
海技术，
在 C# 中，我们如何定义接受 DateTime 对象并返回布尔值的多播委托.
in C#, how can we define the multicast delegate which accepts a DateTime object and return a boolean.
谢谢
推荐答案
public delegate bool Foo(DateTime timestamp);
这是使用您描述的签名声明委托的方法.所有代表都可能是多播的，它们只需要初始化.如:
This is how to declare a delegate with the signature you describe. All delegates are potentially multicast, they simply require initialization. Such as:
public bool IsGreaterThanNow(DateTime timestamp)
{
return DateTime.Now < timestamp;
}
public bool IsLessThanNow(DateTime timestamp)
{
return DateTime.Now > timestamp;
}
Foo f1 = IsGreaterThanNow;
Foo f2 = IsLessThanNow;
Foo fAll = f1 + f2;
调用 fAll，在这种情况下会同时调用 IsGreaterThanNow() 和 IsLessThanNow().
Calling fAll, in this case would call both IsGreaterThanNow() and IsLessThanNow().
这不能让您访问每个返回值.你得到的只是返回的最后一个值.如果要检索每个值，则必须像这样手动处理多播:
What this doesn't do is give you access to each return value. All you get is the last value returned. If you want to retrieve each and every value, you'll have to handle the multicasting manually like so:
List<bool> returnValues = new List<bool>();
foreach(Foo f in fAll.GetInvocationList())
{
returnValues.Add(f(timestamp));
}
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