空类型

• For more examples of nullable types , including boxing behavior , see
  有关可空类型的更多示例（包括装箱行为） ，请参见
• Each instance of a nullable type has two public read - only properties
  可空类型的每个实例都具有两个公共的只读属性：
• Nothing to a variable of a nullable type , you cannot test it for nothing
  赋予可空类型的变量，但无法测试此变量是否为
• Boxed nullable types fully support the functionality of the underlying type
  装箱的可空类型完全支持基础类型的功能：
• If you use a cast , and the nullable type is currently undefined , an
  如果使用强制转换，并且当前未定义可空类型，将发生
• If you try to assign a nullable type to a non - nullable type without using the
  如果在将可空类型分配给非可空类型时不使用
• Examples of nullable types
  可空类型示例
• To retrieve the value of a variable of a nullable type , you should first test its
  要检索可空类型的变量的值，应先测试它的
• Objects based on nullable types are only boxed if the object is non - null
  基于可空类型的对象只在该对象为非空时才会装箱。