asynchronous operations

• If the asynchronous operation completed synchronously ; otherwise ,
  如果异步操作同步完成，则为
• Cancels a pending asynchronous operation
  取消一个挂起的异步操作。
• That stores state information for this asynchronous operation
  ，它存储此异步操作的状态信息。
• Exceptions thrown by the asynchronous operation are thrown from the
  异步操作引发的异常是从end
• Represents progress data reported in an asynchronous operation
  表示异步操作中报告的进度数据。
• An application performing an asynchronous operation can use the
  执行异步操作的应用程序可以使用
• Method to cancel asynchronous operations that have not completed
  方法取消尚未完成的异步操作。
• This delegate is called at the start of an asynchronous operation
  此委托在异步操作开始时调用。
• Gets or sets the result of the asynchronous operation requested
  获取或设置请求的异步操作结果。
• Returns identifies the asynchronous operation that the method started
  标识方法启动的异步操作。