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This article mainly analyzes the relevant knowledge points of how to achieve thread pause and recovery in ManualResetEvent in C#. The content is detailed and easy to understand, and the operation details are reasonable, so it has a certain reference value. If you are interested, you might as well follow the editor and learn more about "how to pause and resume threads in ManualResetEvent in C#".

Background

The other day I encountered a requirement to refresh a third-party UI without third-party source code and intercept the return result of its ajax request. When the result is AVALIABLE, stop the refresh and voice prompt, otherwise continue to refresh.

After analyzing this requirement, it is found that it is necessary to control the pause and start of a refresh cycle, so the pauses and resumes of threads through ManualResetEvent are found on the Internet.

ManualResetEvent introduction

ManualResetEvent is a class that synchronizes the state between threads through a signaling mechanism. There are three common methods:

WaitOne: blocks the current thread until a signal is received

Reset: sets the event state to a non-terminating state, causing threads to block

Set: sets the event state to the terminated state, allowing one or more waiting threads to continue execution

Realization design

1. Request third-party websites through CefSharp's Google browser plug-in

two。 The specific interaction logic is as follows

Start a thread by default and suspend it through WaitOne, waiting for instructions to start automatic refresh manually

Send the start signal manually through the Set method

After performing the face operation, suspend the thread again through Reset, wait for the Ajax result, judge the Ajax result, and resume the thread again if it is not equal to AVALIABLE.

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" / / to avoid page loading, it is recommended to add the sentence Cef.Initialize (setting); workerThread = new Thread (new ThreadStart (BeginListenWorkerAsync)); workerThread.IsBackground = true; workerThread.Start (); this. Stop automatically listening ToolStripMenuItem.Enabled = false;} private async void BeginListenWorkerAsync () {while (true) {_ eventBeginListenWorkList.WaitOne (); / / 1. By default, suspend the thread and wait for the signal 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. After the page performs the corresponding operation, it suspends the thread again, waits for the result of the ajax request to determine whether to resume the thread} private void stops automatically listening to ToolStripMenuItem_Click (object sender, EventArgs e) {this. Start automatically listening to ToolStripMenuItem.Enabled = true; this. Stop automatic listening ToolStripMenuItem.Enabled = false; _ eventBeginListenWorkList.Reset (); StartListen = false;} private void start automatic listening ToolStripMenuItem_Click (object sender, EventArgs e) {this. Start automatically listening to ToolStripMenuItem.Enabled = false; this. Stop automatic listening ToolStripMenuItem.Enabled = true; _ eventBeginListenWorkList.Set (); / / 2. Manually signal the thread to work through Set, StartListen = true;}

3. Now we need to define RequestHandler to specify ResourceHandler to intercept ajax requests

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

Custom ResourceHandler needs to be specified in MyRequestHandler

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) {/ / call the implementation of the base class first, and debug return base.OnBeforeBrowse (chromiumWebBrowser, browser, frame, request, userGesture, isRedirect) at breakpoint. } 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. Finally, after ResourceRequestHandler intercepts the ajax request, if the result is not AVALIABLE, the thread is resumed again through StartListenFunc.

Public class MyResourceRequestHandler: ResourceRequestHandler {Form1 _ form; public MyResourceRequestHandler (Form1 form) {_ form = form;} private Dictionary responseDictionary = new Dictionary (); 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 (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 ();}

On the other hand, StartListenFunc restores the thread's repeated query to ui again through the Set method.

Public static void StartListenFunc () {_ eventBeginListenWorkList.Set (); StartListen = true What is C #? C # is a simple, general-purpose, object-oriented programming language developed by Microsoft Microsoft. It inherits the powerful functions of C and C++, and removes some of their complex features. C # combines the simple visualization of VB and the high efficiency of C++. Because of its strong operational ability, elegant syntax style, innovative language features and convenient component-oriented programming, it has become the preferred language for .NET development, but it is not suitable for writing code with urgent time or very high performance. because C# lacks the key features needed for high-performance applications.

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