对于类型转换运算符，操作数或返回类型必须是类或结构的数据类型。

For a type conversion operator, either the operand or the return type must be of the data type of the class or structure.

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为可空类型提供类库支持，包括转换运算符和算术运算符。

Library Support for nullable types, including conversion operators and arithmetic operators.

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转换的定义方法类似于运算符，并根据它们所转换到的类型命名。

Conversions are defined like operators and are named for the type to which they convert.

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