您缺少添加一些参考的信息.或者，如果您添加了参考，请尝试将using YourNamespace;添加到您的课程中.

^ ]了解更多详细信息.

You are missing to add some reference. Or if you have added a reference, try adding using YourNamespace; to your class.

Google[^] for more details.

如果您不知道要添加哪个名称空间，请执行一件事

将鼠标移至Reader的声明.

鼠标单击阅读器"，然后单击向下箭头，将为您建议该阅读器的名称空间..

对不起，如果我误会你的话

if you dont know which namespace to add then do one thing

move your mouse to the declaration of Reader.

mouse click on "Reader", click down arrow it will suggest you the name spaces for that reader..

sorry if i misunderstad you