C# 什么是设备以及如何使用 lambda 表达式？
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What is appliance and how to use lambda expressions?
提问by Danimal
I've read that Lambda Expressions are an incredibly powerful addition to C#, yet I find myself mystified by them. How can they improve my life or make my code better? Can anyone point to a good resource for learning such expressions?
我读到 Lambda 表达式是 C# 的一个非常强大的补充，但我发现自己对它们感到困惑。他们如何改善我的生活或使我的代码更好？任何人都可以指出学习此类表达的好资源吗？
They seem cool as hell, but how do they relate to my day-to-day life as an asp.net developer?
它们看起来很酷，但它们与我作为 asp.net 开发人员的日常生活有什么关系？
Edit: Thanks for the examples, and thanks for the link to Eric White's articles. I'm still digesting those now. One quick question: are lambda expressions useful for anything other than querying? Every example I've seen has been a query construct.
编辑：感谢您提供示例，并感谢您提供 Eric White 文章的链接。我现在还在消化这些。一个简单的问题：lambda 表达式除了查询之外还有其他用途吗？我见过的每个例子都是一个查询结构。
采纳答案by Will Dean
: are lambda expressions useful for anything other than querying
: lambda 表达式对查询以外的任何事情都有用吗
Lamba expressions are nothing much other than a convenient way of writing a function 'in-line'.
Lamba 表达式只不过是一种“内联”编写函数的便捷方式。
So they're useful any place you wanted a bit of code which can be called as though it's a separate function but which is actually written inside its caller. (In addition to keeping related code in the same location in a file, this also allows you to play fun games with variable scoping - see 'closures' for a reference.)
所以它们在任何你想要一些代码的地方都很有用，这些代码可以被调用，好像它是一个单独的函数，但实际上是在它的调用者内部编写的。（除了将相关代码保存在文件中的同一位置之外，这还允许您玩具有可变作用域的有趣游戏 - 请参阅“闭包”以获取参考。）
An example of a non-query-related use of a lamba might be a bit of code which does something asynchronously that you start with ThreadPool.QueueUserWorkItem. The important point is that you could also write this using anonymous delegates (which were a C#2 introduction), or just a plain separate class member function.
Lamba 的非查询相关使用的一个示例可能是一些代码，它以 ThreadPool.QueueUserWorkItem 开始异步执行某些操作。重要的一点是，您也可以使用匿名委托（这是 C#2 介绍）或仅使用简单的单独类成员函数来编写它。
This http://blogs.msdn.com/jomo_fisher/archive/2005/09/13/464884.aspxis a superb step-by-step introduction into all this stuff, which might help you.
这个http://blogs.msdn.com/jomo_fisher/archive/2005/09/13/464884.aspx是对所有这些东西的极好的逐步介绍，它可能对您有所帮助。
回答by Brian Leahy
Lambdas bring functional programing to C#. They are anonymous functions that can be passed as values to certain other functions. Used most in LINQ.
Lambda 将函数式编程引入 C#。它们是匿名函数，可以作为值传递给某些其他函数。在 LINQ 中使用最多。
Here is a contrived example:
这是一个人为的例子：
List<int> myInts = GetAll();
IEnumerable<int> evenNumbers = myInts.Where(x => x % 2 == 0);
Now when you foreach through evenNumbers the lamda
现在当你通过 evenNumbers foreach lamda
x=> x % 2 == 0
is then applied as a filter to myInts.
然后作为过滤器应用于 myInts。
They become really useful in increasing readability to complicated algorithms that would have many nested IF conditionals and loops.
它们在提高具有许多嵌套 IF 条件和循环的复杂算法的可读性方面变得非常有用。
回答by Corey
Here's a simple example of something cool you can do with lambdas:
这是一个简单的例子，你可以用 lambdas 做一些很酷的事情：
List<int> myList = new List<int>{ 1, 2, 3, 4, 5, 6, 7, 8, 9 };
myList.RemoveAll(x => x > 5);
//myList now == {1,2,3,4,5}
The RemoveAll method takes a predicate(a delegate that takes argurments and returns a bool), any that match it get removed. Using a lambda expression makes it simpler than actually declaring the predicate.
RemoveAll 方法接受一个谓词（一个接受参数并返回一个 bool 的委托），任何匹配它的都被删除。使用 lambda 表达式比实际声明谓词更简单。
