我宁愿不要轮询数据库，因为这会很浪费。我会通过只为我的数据（HTTP API 等）打开一个入口点来解决这个问题，然后通过 SignalR Hub 向所有连接的客户端广播更新。 Brad Wilson 有一个非常酷的演示文稿，展示了这种方法：
Brad Wilson - Microsoft’s Modern Web Stack, Starring ASP.NET Web API
这里是这种方法的代码示例，它使用 ASP.NET Web API 技术进行数据输入。它使用内存中的字典进行数据存储，但这里不关心数据存储技术：
// This hub has no inbound APIs, since all inbound communication is done
// via the HTTP API. It's here for clients which want to get continuous
// notification of changes to the ToDo database.
[HubName("todo")]
public class ToDoHub : Hub { }
public abstract class ApiControllerWithHub<THub> : ApiController
where THub : IHub {
Lazy<IHubContext> hub = new Lazy<IHubContext>(
() => GlobalHost.ConnectionManager.GetHubContext<THub>()
);
protected IHubContext Hub {
get { return hub.Value; }
}
}
public class ToDoController : ApiControllerWithHub<ToDoHub> {
private static List<ToDoItem> db = new List<ToDoItem> {
new ToDoItem { ID = 0, Title = "Do a silly demo on-stage at NDC" },
new ToDoItem { ID = 1, Title = "Wash the car" },
new ToDoItem { ID = 2, Title = "Get a haircut", Finished = true }
};
private static int lastId = db.Max(tdi => tdi.ID);
// Lines removed for brevity
public HttpResponseMessage PostNewToDoItem(ToDoItem item) {
lock (db) {
// Add item to the "database"
item.ID = Interlocked.Increment(ref lastId);
db.Add(item);
// Notify the connected clients
Hub.Clients.addItem(item);
// Return the new item, inside a 201 response
var response = Request.CreateResponse(HttpStatusCode.Created, item);
string link = Url.Link("apiRoute", new { controller = "todo", id = item.ID });
response.Headers.Location = new Uri(link);
return response;
}
}
// Lines removed for brevity
}
还提供了 Brad 演示的应用程序的完整源代码：https://github.com/bradwilson/ndc2012。
另一个您不喜欢的选项是让您的数据库在数据更改后立即触发通知。然后，您可以将其拾取并通过 SignalR 进行广播。这是一个例子：
Database Change Notifications in ASP.NET using SignalR and SqlDependency