本文详细解析了C#和Visual Basic中Nullable类型的使用方法，包括如何标记值类型为可空，以及Nullable<T>结构的支持。介绍了默认情况下，引用类型如String是可空的，而值类型如Int32则不是。通过使用?符号，可以将值类型变为可空，从而能够被赋值为null。
Remarks
A type is said to be nullable if it can be assigned a value or can be assigned null, which means the type has no value whatsoever. By default, all reference types, such as String, are nullable, but all value types, such as Int32, are not.
In C# and Visual Basic, you mark a value type as nullable by using the ? notation after the value type. For example, int? in C# or Integer? in Visual Basic declares an integer value type that can be assigned null.
The Nullable<T> structure supports using only a value type as a nullable type because reference types are nullable by design.
The Nullable class provides complementary support for the Nullable<T> structure. The Nullable class supports obtaining the underlying type of a nullable type, and comparison and equality operations on pairs of nullable types whose underlying value type does not support generic comparison and equality operations.
扫一扫
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
