背景

前些天遇到一个需求，在没有第三方源码的情况下，刷新一个第三方UI，并且拦截到其ajax请求的返回结果。当结果为AVALIABLE的时候，停止刷新并语音提示，否则继续刷新。

分析这个需求，发现需要控制一个刷新循环的暂停与开始，因此网上搜到了通过ManualResetEvent实现线程的暂停与恢复。

ManualResetEvent介绍

ManualResetEvent是一个通过信号机制，实现线程间状态同步的类。常用的方法有以下三个：

WaitOne：阻止当前线程，直到收到信号

Reset：将事件状态设置为非终止状态，导致线程阻止

Set：将事件状态设置为终止状态，从而允许继续执行一个或多个等待线程

实现设计

1.通过CefSharp的谷歌浏览器插件请求第三方网站

 2.具体交互逻辑如下

1. 默认开启一个线程，并通过WaitOne挂起，等待手动开始自动刷新的指令

2. 手动通过Set方法发送开始工作信号

3. 执行完面操作后，通过Reset将线程再次挂起，并等待Ajax结果，判断Ajax结果，如果不等于AVALIABLE则再次恢复线程

public Form1()
{InitializeComponent();var setting = new CefSettings();setting.Locale = "zh-CN";setting.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36";// 避免页面加载不出来, 建议加上这句Cef.Initialize(setting);workerThread = new Thread(new ThreadStart(BeginListenWorkerAsync));workerThread.IsBackground = true;workerThread.Start();this.停止自动监听ToolStripMenuItem.Enabled = false;
}private async void BeginListenWorkerAsync()
{while (true){_eventBeginListenWorkList.WaitOne();  //1.默认挂起线程，等待信号chromiumWebBrowser1.GetBrowser().MainFrame.ExecuteJavaScriptAsync(@"document.evaluate(""//*[@id='root']/div[1]/div[2]/div/div[2]/div[1]/div[1]/div/div[1]/button"", document).iterateNext().click()");Thread.Sleep(1000);chromiumWebBrowser1.GetBrowser().MainFrame.ExecuteJavaScriptAsync(@"document.evaluate(""//*[@id='root']/div[1]/div[2]/div/div[1]/div/div/div/div[2]/div[6]/div/button"", document).iterateNext().click()");_eventBeginListenWorkList.Reset(); //3.页面执行完相应操作则再次挂起线程，等待ajax请求结果再判断是否恢复线程}
}private void 停止自动监听ToolStripMenuItem_Click(object sender, EventArgs e)
{this.开始自动监听ToolStripMenuItem.Enabled = true;this.停止自动监听ToolStripMenuItem.Enabled = false;_eventBeginListenWorkList.Reset();StartListen = false;
}private void 开始自动监听ToolStripMenuItem_Click(object sender, EventArgs e)
{this.开始自动监听ToolStripMenuItem.Enabled = false;this.停止自动监听ToolStripMenuItem.Enabled = true;_eventBeginListenWorkList.Set(); // 2.手动通过Set发送信号恢复线程，让其工作StartListen = true;
}

 3.现在我们需要定义RequestHandler来指定ResourceHandler拦截ajax请求

private void Form1_Load(object sender, EventArgs e)
{chromiumWebBrowser1.RequestHandler = new MyRequestHandler(this);chromiumWebBrowser1.Load("https://www.xxxxxxxx.com/");
}

MyRequestHandler中需要指定自定义ResourceHandler

public class MyRequestHandler : RequestHandler
{Form1 _form;public MyRequestHandler(Form1 form){_form = form;}public static string AuthorizationValue;protected override bool OnBeforeBrowse(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, IRequest request, bool userGesture,bool isRedirect){// 先调用基类的实现，断点调试return base.OnBeforeBrowse(chromiumWebBrowser, browser, frame, request, userGesture, isRedirect);}protected override IResourceRequestHandler GetResourceRequestHandler(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame,IRequest request, bool isNavigation, bool isDownload, string requestInitiator, ref bool disableDefaultHandling){Console.WriteLine(request.Url);if (request.Url.StartsWith("https://www.xxxxxxxxxxxxxxxx/api") && request.Headers.AllKeys.Contains("Authorization")){AuthorizationValue = request.Headers["Authorization"];}return new MyResourceRequestHandler(_form);}
}

4.最后ResourceRequestHandler拦截到ajax请求之后，如果结果不是AVALIABLE则通过StartListenFunc再次恢复线程

public class MyResourceRequestHandler : ResourceRequestHandler
{Form1 _form;public MyResourceRequestHandler(Form1 form){_form = form;}private Dictionary<ulong, MemoryStreamResponseFilter> responseDictionary = new Dictionary<ulong, MemoryStreamResponseFilter>();protected override IResponseFilter GetResourceResponseFilter(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response){var dataFilter = new MemoryStreamResponseFilter();responseDictionary.Add(request.Identifier, dataFilter);return dataFilter;}protected override void OnResourceLoadComplete(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IResponse response, UrlRequestStatus status, long receivedContentLength){MemoryStreamResponseFilter filter;if (responseDictionary.TryGetValue(request.Identifier, out filter)){var data = filter.Data;if (request.Url.StartsWith("https://xxxxxxxxxxxxxxxxxxxx/oneapi")){var available = false;string s = System.Text.Encoding.UTF8.GetString(data, 0, data.Length);Console.WriteLine(s);if (!string.IsNullOrEmpty(s)){var responseData = JsonConvert.DeserializeObject<ScheduleResponse>(s);if (responseData != null && responseData.productPreviews != null){foreach (var item in responseData.productPreviews){if (item.schedule != null && item.schedule.status != null && item.schedule.status.name == "AVAILABLE"){available = true;Mp3Player.Play();Action act = delegate () { _form.StopListen(); };_form.Invoke(act);break;}}}}if (!available && Form1.StartListen){Form1.StartListenFunc();}}filter.Dispose();}}
}

 而StartListenFunc则是通过Set方法再次恢复了线程对ui的重复查询

public static void StartListenFunc()
{_eventBeginListenWorkList.Set();StartListen = true;
}

ManualResetEvent官方介绍如下

https://docs.microsoft.com/zh-cn/dotnet/api/system.threading.manualresetevent?view=netframework-1.1