C#中的回调 [英] Callbacks in C#

问题描述

我想要一个库，里面有一个函数，它接受一个对象作为它的参数.

I want to have a library that will have a function in it that accepts an object for it's parameter.

有了这个对象，我希望能够在 X 完成时调用指定的函数.将调用的函数由调用者指定，X由库完成和监控.

With this object I want to be able to call a specified function when X is finished. The function that will be called is to be specified by the caller, and X will be done and monitored by the library.

我该怎么做?

作为参考，我使用的是 C# 和 .NET 3.5

For reference I'm using C# and .NET 3.5

推荐答案

两个选项:

1. 让函数接受 委托(Action 用于不返回任何内容的回调，Func 一个这样做)并在调用它时使用匿名委托或 Lambda 表达式.

1. Have the function accept a delegate (Action for a callback that doesn't return anything, Func for one that does) and use an anonymous delegate or Lambda Expression when calling it.

使用界面

使用委托/lambda

public static void DoWork(Action processAction)
{
  // do work
  if (processAction != null)
    processAction();
}

public static void Main()
{
  // using anonymous delegate
  DoWork(delegate() { Console.WriteLine("Completed"); });

  // using Lambda
  DoWork(() => Console.WriteLine("Completed"));
}

如果你的回调需要传递一些东西，你可以在Action上使用一个类型参数:

If your callback needs to have something passed to it, you can use a type parameter on Action:

public static void DoWork(Action<string> processAction)
{
  // do work
  if (processAction != null)
    processAction("this is the string");
}

public static void Main()
{
  // using anonymous delegate
  DoWork(delegate(string str) { Console.WriteLine(str); });

  // using Lambda
  DoWork((str) => Console.WriteLine(str));
}

如果需要多个参数，可以在Action中添加更多类型参数.如果您需要返回类型，如上所述使用 Func 并使返回类型成为 last 类型参数(Func 是一个函数接受一个字符串并返回一个整数.)

If it needs multiple arguments, you can add more type parameters to Action. If you need a return type, as mentioned use Func and make the return type the last type parameter (Func<string, int> is a function accepting a string and returning an int.)

有关代表的更多信息 这里.

More about delegates here.

public interface IObjectWithX
{
  void X();
}

public class MyObjectWithX : IObjectWithX
{
  public void X()
  {
    // do something
  }
}

public class ActionClass
{
  public static void DoWork(IObjectWithX handlerObject)
  {
    // do work
    handlerObject.X();
  }
}

public static void Main()
{
  var obj = new MyObjectWithX()
  ActionClass.DoWork(obj);
}

这篇关于C#中的回调的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！