System.Nullable< T>什么是空* int值的价值？ [英] System.Nullable<T> What is the value of null * int value?

问题描述

考虑下面的语句：

int? v1 = null;

int? v2 = 5 * v1;

什么是 V2 的价值？ （空或空字符串？）

What is the value of v2? (null or empty string?)

如何防止编译器将其标记为无效操作？我是否需要遵循自定义异常处理？

How can I prevent the compiler to mark it as invalid operation? Do I need to follow custom exception handling?

推荐答案

这是空。

对于二元运算符 + - * / ％ &安培; | ^ << >> ：

C# Language Specification 3.0 (Section §7.2.7: Lifted operators)

For the binary operators + - * / % & | ^ << >> :

运算符的提升形式存在，如果操作数和结果类型都为非可空值类型。该提升形式是通过将一个？修改到每个操作数和结果类型构造的。 提升运算产生了空价值，如果一个或两个操作数是空 （异常作为&放大器; 和 | 的布尔运营商型，如在§7.10.3描述）。否则，提升运算解开操作数，应用基础运算符，并包装结果。

a lifted form of an operator exists if the operand and result types are all non-nullable value types. The lifted form is constructed by adding a single ? modifier to each operand and result type. The lifted operator produces a null value if one or both operands are null (an exception being the & and | operators of the bool? type, as described in §7.10.3). Otherwise, the lifted operator unwraps the operands, applies the underlying operator, and wraps the result.

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如何防止编译器将其标记为无效操作？我是否需要遵循自定义异常处理？

How can I prevent the compiler to mark it as invalid operation? Do I need to follow custom exception handling?

这不是一个无效的操作。它不会抛出异常，所以你不必处理这种情况下的例外。

It's not an invalid operation. It won't throw an exception so you don't need to handle exceptions in this case.

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