C#中的花括号 [英] Curly Braces In C#

问题描述

我在玩一些代码，我想知道是否有人可以告诉我这段代码中的大括号代表什么.我以为这是一个空对象，但似乎并非如此.

I was playing around with some code and I was wondering if any can tell me what the curly braces in this code represents. I thought it would've been for an empty object but that doesn't seem to be the case.

 Person person = new Person{};

            if (person is {}){
                Console.WriteLine("Person is empty.");
            } else {
                Console.WriteLine("Person is not empty.");
            }

它编译得很好；但是如果我填充 person 类的属性，它仍然属于 if 语句的 person is empty 部分.

It compiles just fine; but if I populate the properties of the person class it still falls into the person is empty part of the if statement.

推荐答案

{} 在此上下文中表示任何类型的模式匹配以检查实例是否不为空:

{} means in this context a pattern matching of any type to check if the instance is not null:

if(person != null){     //the same as: if(person is {})...

}

它就像一个用于模式匹配的 var 关键字，因此您不需要显式指定/重复类型(尽管您知道).

It is like a var keyword for pattern matching, so you do not need to specify/repeat the type explicitly (although you know it).

if(GetPersonFromDb() is {} person){     //the same as: var person = GetPersonFromDb(); if(person != null)...

}

更多信息(请参阅特殊匹配表达式部分):https://hackernoon.com/whats-pattern-matching-in-c-80-6l7h3ygm

More info (see the section Special match expressions): https://hackernoon.com/whats-pattern-matching-in-c-80-6l7h3ygm

这篇关于C#中的花括号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！