什么是动作<字符串>? [英] What is Action<string>?

问题描述

什么是Action<string>，怎么用?

推荐答案

Action 是一个标准委托，有 1 到 4 个参数(.NET 4 中为 16 个)并且不返回值.它用于表示一个动作.

Action is a standard delegate that has one to 4 parameters (16 in .NET 4) and doesn't return value. It's used to represent an action.

Action<String> print = (x) => Console.WriteLine(x);

List<String> names = new List<String> { "pierre", "paul", "jacques" };
names.ForEach(print);

还有其他预定义的委托:

There are other predefined delegates :

• 谓词，有一个参数并返回一个布尔值的委托.

• Predicate, delegate that has one parameter and returns a boolean.

Predicate<int> predicate = ((number) => number > 2);
var list = new List<int> { 1, 1, 2, 3 };
var newList = list.FindAll(predicate);

Func 是更通用的一个，它有 1 到 4 个参数(.NET 4 中为 16 个)并返回一些东西

Func is the more generic one, it has 1 to 4 parameters (16 in .NET 4) and returns something

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