https://msdn.microsoft.com/en-us/library/dn636893(v=vs.110).aspx

文档中这样描述：

Differs from a normal ThreadPool work item in that ASP.NET can keep track of how many work items registered through this API are currently running, and the ASP.NET runtime will try to delay AppDomain shutdown until these work items have finished executing. This API cannot be called outside of an ASP.NET-managed AppDomain. The provided CancellationToken will be signaled when the application is shutting down.

QueueBackgroundWorkItem takes a Task-returning callback; the work item will be considered finished when the callback returns.

其中 and the ASP.NET runtime will try to delay AppDomain shutdown until these work items have finished executing。

try to delay 。是不是 ‘不保证在 AppDomain 关闭之前， 等待 WorkItem 完成执行’ 的意思。