如何从应该返回整数的函数返回 null

Question

在一次采访中，有人问我如何从整数、双精度类型等的方法中返回 Null，而无需任何输出参数。

Answer 1

你可以做这样的事情。您必须首先使int类型可为空。通过int? 正常使用intc# 中的数据类型默认情况下不可为空，因此您必须将int //not nullable类型显式转换为int? //nullable你可以用 double 等做同样的事情。// the return-type is int?. So you can return 'null' value from it.public static int? method()&nbsp;{&nbsp; &nbsp;return null;}也可以这样写上面的方法：// this is another way to convert "non-nullable int" to "nullable int".public static Nullable<int> method(){&nbsp; &nbsp;return null;}

Answer 2

如果目的是从返回类型为 int 的函数返回 null 值，那么您可以执行以下操作：public static int method(){&nbsp; &nbsp; Nullable<int> i = null;&nbsp; &nbsp; if (!i.HasValue)&nbsp; &nbsp; &nbsp; &nbsp; throw new NullReferenceException();&nbsp; &nbsp; else&nbsp; &nbsp; &nbsp; &nbsp; return 0;}public static void Main(){&nbsp; &nbsp; int? i = null;&nbsp; &nbsp; try&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; i = method();&nbsp; &nbsp; }&nbsp; &nbsp; catch (NullReferenceException ex)&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; i = null;&nbsp; &nbsp; }&nbsp; &nbsp; finally&nbsp;&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; // null value stored in the i variable will be available&nbsp; &nbsp; }}

Answer 3

您必须将返回类型声明为可为空的 int。这样你就可以返回一个 Int 或 null。请参见下面的示例：private int? AddNumbers(int? First, int? Second){&nbsp; &nbsp;return First + Second;}