前台关闭iframe页面时把iframe从内存中清理

                                    var iframe = $('#' + iframeID).prop('contentWindow');
                                    $('#' + iframeID).attr('src', 'about:blank');
                                    try {
                                        iframe.document.write('');
                                        iframe.document.clear();
                                    } catch (e) { }
                                    //把iframe从页面移除 
                                    $('#' + iframeID).remove();

后台使用SignalR Hub的关闭连接事件，线程取消 CancellationTokenSource 对象一定要使用静态变量

using HenryMes.Model;
using Microsoft.AspNet.SignalR;
using Microsoft.AspNet.SignalR.Hubs;
using System;
using System.Threading;
using System.Threading.Tasks;

namespace HenryMes.WebProtal.SignalR.OEE.Equipment
{
    [HubName("OEEEquipmentHub")]
    public class OEEEquipmentHub : Hub
    {
        private static CancellationTokenSource tokenSource = new CancellationTokenSource();
        private static CancellationToken token;

        /// <summary>
        /// 
        /// </summary>
        /// <param name="connectId">连接ID</param>
        /// <param name="id">设备ID</param>
        public void Send(string connectId, string id)
        {
            if (string.IsNullOrEmpty(id))
                return;

            if (tokenSource.IsCancellationRequested)
            {
                tokenSource = new CancellationTokenSource();
            }

            token = tokenSource.Token;
            Task.Run(() =>
            {
                while (!token.IsCancellationRequested)
                {
                    try
                    {
                        var model = new OEEEquipmentModel();
                        Random rnd = new Random(System.Guid.NewGuid().GetHashCode());

                        //完成率
                        model.wan_cheng_lu = rnd.Next(10, 90).ToString();
                        //总在线时间
                        model.zong_zai_xian_shi_jian = rnd.Next(10, 90).ToString();
                        //总故障时间
                        model.zong_gu_zhang_shi_jian = rnd.Next(10, 90).ToString();
                        //计划停机时间
                        model.ji_hua_ting_ji_shi_jian = rnd.Next(10, 90).ToString();
                        //理想运行时间
                        model.li_xiang_yun_xing_shi_jian = rnd.Next(10, 90).ToString();
                        //总运行时间
                        model.zong_yun_xing_shi_jian = rnd.Next(10, 90).ToString();
                        //实际运行时间
                        model.shi_ji_yun_xing_shi_jian = rnd.Next(10, 90).ToString();
                        //可用率
                        model.ke_yong_lu = rnd.Next(10, 90).ToString();
                        //推送到前端
                        OEEEquipmentNotifier.RefreshEquipment(connectId, model);
                    }
                    catch (Exception ex)
                    {

                    }
                    //2秒推送一次
                    Thread.Sleep(2000);
                }
            }, token);
        }

        public override Task OnDisconnected(bool stopCalled)
        {
            if (_connections.Contains(Context.ConnectionId))
            {
                _connections.Remove(Context.ConnectionId);
            }
            try
            {
                if (_connections.Count == 0)
                {
                    _tokenSource.Cancel();
                    _tokenSource.Dispose();
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }
            return base.OnDisconnected(stopCalled);
        }
    }
}

前台使用SignalR建立连接

var myHub = $.connection.OEEFactoryHub;
$.connection.hub.stop();
$.connection.hub.start().done(function () {
    //客户端发送信息到服务器
    myHub.server.send($.connection.hub.id);
});

前台接收后台推送过来的数据，并注册关闭页面的事件(在页面关闭时关闭SignalR)

    //后端设备信息推送到前端
    myHub.client.RefreshFactory = function (message) {
        //总在线时间
        app.zong_zai_xian_shi_jian = message.zong_zai_xian_shi_jian;
        //总故障时间
        app.zong_gu_zhang_shi_jian = message.zong_gu_zhang_shi_jian;
        //计划停机时间
        app.ji_hua_ting_ji_shi_jian = message.ji_hua_ting_ji_shi_jian;
        //理想运行时间
        app.li_xiang_yun_xing_shi_jian = message.li_xiang_yun_xing_shi_jian;
        //总运行时间
        app.zong_yun_xing_shi_jian = message.zong_yun_xing_shi_jian;
        //实际运行时间
        app.shi_ji_yun_xing_shi_jian = message.shi_ji_yun_xing_shi_jian;
        //可用率
        app.ke_yong_lu = message.ke_yong_lu;
        //设备数量
        app.she_bei_shu_liang = message.she_bei_shu_liang;
        //停机数量
        app.ting_ji_shu_liang = message.ting_ji_shu_liang;
        //故障数量
        app.gu_zhang_shu_liang = message.gu_zhang_shu_liang;
        //运行数量
        app.yun_xing_shu_liang = message.yun_xing_shu_liang;
        app.echartsWorkshopProduction();
    };

    window.onbeforeunload = function (e) {
        $.connection.hub.stop();
    };