如本文第一部分所述 （.chm文件 - 请参阅下面的注释） 
 
 
 
 单向调用不等同于异步调用。 当单向呼叫到达服务时，它们可能不会立即全部调度，并且可能在服务端排队等待一次调度一次......如果排队消息的数量超过了队列的容量，那么即使发出单向呼叫，客户端也会阻止。 
 
 
 如果调用单向调用，它何时将控制权返回给调用者？ 同一篇文章的介绍指出单向调用用于即发即弃操作 ，从而模拟一种异步调用。 如果会话WCF服务具有启动会话的Login（）单向方法，此方法何时将控制权返回给调用者？ 是否在方法实际执行服务之前返回？ 如果是这样，我怎么能确定该方法是在服务上执行的？ 
 
 如果我希望服务返回到客户端登录过程中可能发生的错误，那么异步调用是实现“即发即弃”行为的唯一方法吗？ 
 
 
 注意：上面引用的文章来自一篇名为WCF Essentials的文章- 你需要了解的关于单向调用，回调和事件的内容由Juval Lowy提供，可以在2006年10月的MSDN杂志中找到。 上面的链接是MSDN上的帮助文件（.chm）格式。 如果您无法使链接的CHM文件起作用（我不能），您可以使用7zip打开它。 

As stated in the first section of this article (.chm file - see note below)
 
 
 
One-way calls do not equate to asynchronous calls. When one-way calls reach the service, they may not be dispatched all at once and may be queued up on the service side to be dispatched one at a time... If the number of queued messages has exceeded the queue's capacity, then the client will block, even when issuing a one-way call.
 
 
If a one-way call is invoked, when does it return control to the caller? The introduction of the same article states that one-way calls are used for fire-and-forget operations, thereby simulating a kind of asynchronous call. If a sessionful WCF service has a Login() one-way method which starts the session, when does this method return control to the caller? Does it return before the method is actually executed on the service? If so, how can I be sure that the method was performed on service?
 
If I wanted the service to return to the client the possible errors that occur during the login procedure, would be an asynchronous call the only way to achieve a fire-and-forget behaviour?
 
 
Note: The quote above is taken from an article called WCF Essentials - What You Need To Know About One-Way Calls, Callbacks, And Events by Juval Lowy, and can be found in the October 2006 issue of MSDN magazine. The link above is to a help file (.chm) format on MSDN. If you can't get the linked CHM file to work (I couldn't) you can open it with 7zip.

原文：https://stackoverflow.com/questions/12112926