公共actionresult细节（int？Id）写int的目的是什么？ ID ......？ [英] Public actionresult details(int? Id) what is purpose of writing int ? id ......?

问题描述

plz告诉我......如果写int是什么目的？ id in detail（）action meathod



我尝试过：



i试过......它是一个外卡字符，如*？

plz Tell me..what is purpose if writing int ? id in detail() action meathod

What I have tried:

i have tried ... is it a wild card character like * ?

推荐答案

它不是一个通配符说明符，它是一个语言元素。

It's not a "wildcard" specifier, it's a language element.

int x;

创建一个值类型整数，这意味着它不能包含除通常的整数值范围：2147483647到-2147483648（含）。具体来说，因为它是一个值类型，当你添加问号时它不能包含 null 。

：

creates a value type integer which means that it cannot contain anything other than the usual range of integer values: 2147483647 to -2147483648 inclusive. Specifically, because it is a value type, it can't contain null.
when you add the question mark:

int? x;

您正在创建一个可以为空的整数 - 一个可以包含相同范围的值，但也可以包含 null

可空类型（C＃编程指南） [ ^ ]

这些可以是PITA，所以除非你需要，否则不要使用它们。

You are creating a nullable integer - one which can contain the same range of values, but can also contain null
Nullable Types (C# Programming Guide)[^]
These can be a PITA to work with, so don't use them unless you need them.

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