为什么输入“int"永远不等于“空"?

Why type quot;intquot; is never equal to #39;null#39;?(为什么输入“int永远不等于“空?)

问题描述

int n == 0;

if (n == null)    
{  
    Console.WriteLine("......");  
}

表达式 (n == null) 的结果是否总是 false 因为
 int  类型的值永远不等于  null 类型 int?(见下面的警告)

Is it true that the result of expression (n == null) is always false since
a   value of type int  is never equal to   null of type int? (see warning below)

警告 CS0472 表达式的结果始终为false"，因为int"类型的值永远不会等于int"类型的null"?

Warning CS0472 The result of the expression is always 'false' since a value of type 'int' is never equal to 'null' of type 'int?'

推荐答案

如果您希望整数变量允许空值，请将其声明为 可空类型:

If you want your integer variable to allow null values, declare it to be a nullable type:

int? n = 0;

注意 int 之后的 ?，这意味着该类型可以具有值 null..NET Framework v2.0 引入了可空类型.

Note the ? after int, which means that type can have the value null. Nullable types were introduced with v2.0 of the .NET Framework.

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