一个非常简单的 ASP.NET MVC 示例：长轮询（又叫：反向 AJAX，英文名：Comet）实现...

关于 长轮询（又叫：反向 AJAX，英文名：Comet）的介绍，请查看：反向Ajax，第1部分：Comet介绍

下面是代码实现：

UI:

<p><input type="button" onclick="longPolling();" value="开始长轮询" />
</p><div><p>服务器返回的信息：</p><p id="msgContainer"></p>
</div>
<script type="text/javascript">function longPolling(){$.getJSON("@Url.Action("GetTime", "DateTime")", function (json){$("#msgContainer").append(json.date + "<br/>");longPolling();});}
</script>

后台代码：

public class DateTimeController : AsyncController
{public DateTimeController(){}public void GetTimeAsync(){//计时器，5秒种触发一次Elapsed事件        System.Timers.Timer timer = new System.Timers.Timer(5000);//告诉.NET接下来将进行一个异步操作       
        AsyncManager.OutstandingOperations.Increment();//订阅计时器的Elapsed事件    timer.Elapsed += (sender, e) =>{//保存将要传递给GetTimeCompleted的参数                AsyncManager.Parameters["nowdate"] = e.SignalTime;//告诉ASP.NET异步操作已完成，进行GetTimeCompleted方法的调用               
            AsyncManager.OutstandingOperations.Decrement();};//启动计时器       
        timer.Start();}public ActionResult GetTimeCompleted(DateTime nowdate){return Json(new { date = nowdate.ToString("HH:mm:ss") + "  Welecom " }, JsonRequestBehavior.AllowGet);}
}

运行效果图：

另一个示例：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Threading.Tasks;
using System.IO;namespace TestMvc.MvcUI.Controllers
{public class ArticleController : AsyncController{#region 方式 1public void ArticleAsync(string name){AsyncManager.OutstandingOperations.Increment();Task.Factory.StartNew(() =>{string path = ControllerContext.HttpContext.Server.MapPath(string.Format(@"\articles\{0}.html", name));using (StreamReader reader = new StreamReader(path)){AsyncManager.Parameters["content"] = reader.ReadToEnd();}AsyncManager.OutstandingOperations.Decrement();});}public ActionResult ArticleCompleted(string content){return Content(content);}#endregion#region 方式 2public Task<ActionResult> Article(string name){return Task.Factory.StartNew(() =>{string path = ControllerContext.HttpContext.Server.MapPath(string.Format(@"\articles\{0}.html", name));using (StreamReader reader = new StreamReader(path)){AsyncManager.Parameters["content"] = reader.ReadToEnd();}}).ContinueWith<ActionResult>(task =>{string content = (string)AsyncManager.Parameters["content"];return Content(content);});}#endregion#region 方式 3public Task<ActionResult> Article2(string name){return Task.Factory.StartNew(() =>{string path = ControllerContext.HttpContext.Server.MapPath(string.Format(@"\articles\{0}.html", name));using (StreamReader reader = new StreamReader(path)){return reader.ReadToEnd();}}).ContinueWith<ActionResult>(task =>{return Content((string)task.Result);});}#endregion}
}

查考自：.Net MVC 实现长轮询

谢谢浏览！