摘要
在ews中提供了一种拉通知的方式获取服务端邮件的操作，通过这种方式客户端可以订阅该通知，在邮箱有变化的时候，可以收到通知。
工作方式
EWS 通知是在订阅的基础上处理的。通常是一个订阅每个邮箱，以及邮箱订阅中您可以订阅部分或全部文件夹。您决定何种通知订阅 (流、 请求或推) 以及哪种类型的事件您想要接收 (NewMail，创建、 删除、 修改日期，等等)，然后创建订阅。EWS 事件然后发送以异步方式从邮箱服务器到客户端。
EWS 流式处理通知
通知依赖悬挂 get 请求在服务器上保留流订阅连接以便连接处于活动状态时所发生的任何事件传送到客户端立即打开。过程中的一个连接，并连接保持打开直到间隔过期，或最多 30 分钟可以发送多个通知。连接到期后，客户端发送悬挂再次 get 请求。图 2 显示了流订阅和流式处理通知的工作方式。
EWS 拉通知
通知依赖于在客户端上的时间间隔，客户端管理通知的请求。这可能会导致任何的通知与 GetEvents 响应。图 3 显示了请求订阅和请求通知的工作方式。
一个例子
ExchangeService service = Main(Box);
Timer mytimer = +==
</span><span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> mytimer_Elapsed(<span style="color: #0000ff;">object</span><span style="color: #000000;"> sender,ElapsedEventArgs e)
{
Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">running</span><span style="color: #800000;">"</span><span style="color: #000000;">);
GetPullNotifications();
}
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> SubscribePullNotifications(FolderId folderId)
{
service.Url </span>= <span style="color: #0000ff;">new</span> Uri(<span style="color: #800000;">"</span><span style="color: #800000;">https://mail.testsssss.com/ews/exchange.asmx</span><span style="color: #800000;">"</span><span style="color: #000000;">);
service.Credentials </span>= <span style="color: #0000ff;">new</span> NetworkCredential(<span style="color: #800000;">"</span><span style="color: #800000;">www</span><span style="color: #800000;">"</span>,<span style="color: #800000;">"</span><span style="color: #800000;">12345</span><span style="color: #800000;">"</span>,<span style="color: #800000;">"</span><span style="color: #800000;">domain</span><span style="color: #800000;">"</span><span style="color: #000000;">);
Subscription </span>= service.SubscribeToPullNotifications(<span style="color: #0000ff;">new</span> FolderId[] { folderId },<span style="color: #800080;">1440</span>,<span style="color: #0000ff;">null</span><span style="color: #000000;">,EventType.NewMail,EventType.Created,EventType.Deleted);
}
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> GetPullNotifications()
{
IEnumerable</span><ItemEvent> itemEvents =<span style="color: #000000;"> Subscription.GetEvents().ItemEvents;
</span><span style="color: #0000ff;">foreach</span> (ItemEvent itemEvent <span style="color: #0000ff;">in</span><span style="color: #000000;"> itemEvents)
{
</span><span style="color: #0000ff;">switch</span><span style="color: #000000;"> (itemEvent.EventType)
{
</span><span style="color: #0000ff;">case</span><span style="color: #000000;"> EventType.Copied:
Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Copied</span><span style="color: #800000;">"</span><span style="color: #000000;">);
</span><span style="color: #0000ff;">break</span><span style="color: #000000;">;
</span><span style="color: #0000ff;">case</span><span style="color: #000000;"> EventType.Created:
Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Created</span><span style="color: #800000;">"</span><span style="color: #000000;">);
</span><span style="color: #0000ff;">break</span><span style="color: #000000;">;
</span><span style="color: #0000ff;">case</span><span style="color: #000000;"> EventType.Deleted:
Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Deleted</span><span style="color: #800000;">"</span><span style="color: #000000;">);
</span><span style="color: #0000ff;">break</span><span style="color: #000000;">;
</span><span style="color: #0000ff;">case</span><span style="color: #000000;"> EventType.FreeBusyChanged:
Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">FreeBusyChanged</span><span style="color: #800000;">"</span><span style="color: #000000;">);
</span><span style="color: #0000ff;">break</span><span style="color: #000000;">;
</span><span style="color: #0000ff;">case</span><span style="color: #000000;"> EventType.Modified:
Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Modified</span><span style="color: #800000;">"</span><span style="color: #000000;">);
</span><span style="color: #0000ff;">break</span><span style="color: #000000;">;
</span><span style="color: #0000ff;">case</span><span style="color: #000000;"> EventType.Moved:
Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Moved</span><span style="color: #800000;">"</span><span style="color: #000000;">);
</span><span style="color: #0000ff;">break</span><span style="color: #000000;">;
</span><span style="color: #0000ff;">case</span><span style="color: #000000;"> EventType.NewMail:
Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">New mail</span><span style="color: #800000;">"</span><span style="color: #000000;">);
Console.WriteLine(itemEvent.ItemId.UniqueId);
EmailMessage emailMessage </span>=<span style="color: #000000;"> EmailMessage.Bind(service,itemEvent.ItemId.UniqueId);
Console.WriteLine(emailMessage.Subject);
Console.WriteLine(emailMessage.Body.Text);
Console.WriteLine(emailMessage.From);
Console.WriteLine(emailMessage.DateTimeReceived);
Console.WriteLine(</span><span style="color: #0000ff;">string</span>.Join(<span style="color: #800000;">"</span><span style="color: #800000;">;</span><span style="color: #800000;">"</span>,emailMessage.ToRecipients.Select(x =><span style="color: #000000;"> x.Address).ToArray()));
</span><span style="color: #0000ff;">break</span><span style="color: #000000;">;
</span><span style="color: #0000ff;">case</span><span style="color: #000000;"> EventType.Status:
Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">Status</span><span style="color: #800000;">"</span><span style="color: #000000;">);
</span><span style="color: #0000ff;">break</span><span style="color: #000000;">;
</span><span style="color: #0000ff;">default</span><span style="color: #000000;">:
</span><span style="color: #0000ff;">break</span><span style="color: #000000;">;
}
}
}
}
}
开始监听
当收到新的邮件时，eventType为NewMail，可以根据uniqueid查询当前邮件详情。
参考资料
