Message in Chinese (Simplified) (中文(简体))
从异步“Begin”方法返回的值或传递给 AsyncCallback 的值为 null。异步“Begin”实现必须返回非 null 的 IAsyncResult，并将同一 IAsyncResult 对象作为参数传递给 AsyncCallback。
Unlocalized message
A null value was returned from an async 'Begin' method or passed to an AsyncCallback. Async 'Begin' implementations must return a non-null IAsyncResult and pass the same IAsyncResult object as the parameter to the AsyncCallback.
Search by Google