如何转换函数功能&LT; T,布尔&GT;以predicate&LT; T&GT;? [英] How to convert Func<T, bool> to Predicate<T>?
问题描述
是的,我已经看到了这但我找不到答案,我的具体的问题。
Yes I've seen this but I couldn't find the answer to my specific question.
由于一个lambda testLambda 这需要T和返回一个布尔值(我可以使它无论是predicate或函数功能即是给我)
Given a lambda testLambda that takes T and returns a boolean (I can make it either Predicate or Func that's up to me)
我需要能够同时使用List.FindIndex(testLambda)(花费predicate)和List.Where(testLambda)(需要一个Func键)。
I need to be able to use both List.FindIndex(testLambda) (takes a Predicate) and List.Where(testLambda) (takes a Func).
任何想法如何做到既?
推荐答案
简单:
Func<string,bool> func = x => x.Length > 5;
Predicate<string> predicate = new Predicate<string>(func);
基本上,你可以创建任何的兼容的现有实例中一个新委托实例。这也支持差异(合作和反 - ):
Basically you can create a new delegate instance with any compatible existing instance. This also supports variance (co- and contra-):
Action<object> actOnObject = x => Console.WriteLine(x);
Action<string> actOnString = new Action<string>(actOnObject);
Func<string> returnsString = () => "hi";
Func<object> returnsObject = new Func<object>(returnsString);
如果你想使通用的:
static Predicate<T> ConvertToPredicate<T>(Func<T, bool> func)
{
return new Predicate<T>(func);
}
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