問題描述
表達(dá)式 (n == null) 的結(jié)果是否總是 false 因?yàn)?br> int 類型的值永遠(yuǎn)不等于 null 類型 int?(見下面的警告)
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 表達(dá)式的結(jié)果始終為false"，因?yàn)閕nt"類型的值永遠(yuǎn)不會(huì)等于int"類型的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?'
推薦答案
如果您希望整數(shù)變量允許空值，請(qǐng)將其聲明為 可空類型:
If you want your integer variable to allow null values, declare it to be a nullable type:
注意 int 之后的 ?，這意味著該類型可以具有值 null..NET Framework v2.0 引入了可空類型.
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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