From: 011netservice@gmail.com Date: 2024-03-01 Subject: AutoResetEvent.txt 歡迎來信交流, 訂購軟體需求. 以下 #### 標記段落, **** 標記常用(流程、設定、備忘) 摘要: signaled state: 立刻執行, 不等待. non-signaled state: 等待到 signaled 再執行. private static AutoResetEvent event_1 = new AutoResetEvent(true); // Created in the signaled state. private static AutoResetEvent event_2 = new AutoResetEvent(false); // Created in the non-signaled state. event_1.Set(); // 設定立刻執行狀態 Sets the state of the event to signaled, allowing one or more waiting threads to proceed. event_1.Reset(); // 設定為等待執行狀態 Sets the state of the event to nonsignaled, causing threads to block. event_1.WaitOne(); // 等待到 signaled 再執行, Blocks the current thread until the current WaitHandle receives a signal. event_1.WaitOne(int); // 等待到 int milliseconds 再執行, Blocks the current thread until the current WaitHandle receives a signal, using a 32-bit signed integer to specify the time interval in milliseconds. event_1.WaitOne(int, bool); // Blocks the current thread until the current WaitHandle receives a signal, using a 32-bit signed integer to specify the time interval and specifying whether to exit the synchronization domain before the wait. event_1.WaitOne(TimeSpan); // 等待到 TimeSpan 再執行, Blocks the current thread until the current instance receives a signal, using a TimeSpan to specify the time interval. event_1.WaitOne(TimeSpan, bool); // Blocks the current thread until the current instance receives a signal, using a TimeSpan to specify the time interval and specifying whether to exit the synchronization domain before the wait. 注意 AutoResetEvent 為 IDisposable interface, 最後一定要 Dispose! #### AutoResetEvent Class **** example The following code example shows how to use a wait handle to keep a process from terminating while it waits for a background thread to finish executing. https://learn.microsoft.com/en-us/dotnet/api/system.threading.waithandle.waitone?view=net-8.0#system-threading-waithandle-waitone(system-int32) If millisecondsTimeout is zero, the method does not block. It tests the state of the wait handle and returns immediately. The caller of this method blocks until the current instance receives a signal or a time-out occurs. Use this method to block until a WaitHandle receives a signal from another thread, such as is generated when an asynchronous operation completes. For more information, see the IAsyncResult interface. Override this method to customize the behavior of derived classes. Calling this method overload is the same as calling the WaitOne(Int32, Boolean) overload and specifying false for exitContext. using System; using System.Threading; class WaitOne { static AutoResetEvent autoEvent = new AutoResetEvent(false); // 建立 AutoResetEvent, signal=false. static void Main() { Console.WriteLine("Main starting."); ThreadPool.QueueUserWorkItem( new WaitCallback(WorkMethod), autoEvent); // Wait for work method to signal. // return true if the current instance receives a signal; otherwise, false if(autoEvent.WaitOne(1000)) // 暫停執行. (等待1秒或 signal = true 時再執行). { Console.WriteLine("Work method signaled."); // signaled, signal=true, 回傳值=true. } else { Console.WriteLine("Timed out waiting for work method to signal."); // 超時, 回傳值=false. } Console.WriteLine("Main ending."); } static void WorkMethod(object stateInfo) { Console.WriteLine("Work starting."); // Simulate time spent working. Thread.Sleep(new Random().Next(100, 2000)); // 停止執行目前 thread 一段時間. // Signal that work is finished. Console.WriteLine("Work ending."); ((AutoResetEvent)stateInfo).Set(); // 發出 signal = true. } } **** https://learn.microsoft.com/en-us/dotnet/api/system.threading.autoresetevent?view=net-8.0&devlangs=csharp&f1url=%3FappId%3DDev17IDEF1%26l%3DEN-US%26k%3Dk(System.Threading.AutoResetEvent)%3Bk(SolutionItemsProject)%3Bk(DevLang-csharp)%26rd%3Dtrue#examples Represents a thread synchronization event that, when signaled, resets automatically after releasing a single waiting thread. This class cannot be inherited. public AutoResetEvent (bool initialState); initialState : Boolean true to set the initial state to signaled; ==> WaitOne()立刻執行, 不等待. false to set the initial state to non-signaled. ==> WaitOne()等待執行, 直到 Set() **** Example1 using System; using System.Threading; namespace AutoResetEvent_Examples { class MyMainClass { //Initially not signaled. const int numIterations = 100; static AutoResetEvent myResetEvent = new AutoResetEvent(false); static int number; static void Main() { //Create and start the reader thread. Thread myReaderThread = new Thread(new ThreadStart(MyReadThreadProc)); myReaderThread.Name = "ReaderThread"; myReaderThread.Start(); for(int i = 1; i <= numIterations; i++) { Console.WriteLine("Writer thread writing value: {0}", i); number = i; //Signal that a value has been written. myResetEvent.Set(); //Give the Reader thread an opportunity to act. Thread.Sleep(1); } //Terminate the reader thread. myReaderThread.Abort(); } static void MyReadThreadProc() { while(true) { //The value will not be read until the writer has written // at least once since the last read. myResetEvent.WaitOne(); Console.WriteLine("{0} reading value: {1}", Thread.CurrentThread.Name, number); } } } } **** Example2 The following example shows how to use AutoResetEvent to release one thread at a time, by calling the Set method (on the base class) each time the user presses the Enter key. The example starts three threads, which wait on an AutoResetEvent that was created in the signaled state. The first thread is released immediately, because the AutoResetEvent is already in the signaled state. This resets the AutoResetEvent to the non-signaled state, so that subsequent threads block. The blocked threads are not released until the user releases them one at a time by pressing the Enter key. After the threads are released from the first AutoResetEvent, they wait on another AutoResetEvent that was created in the non-signaled state. All three threads block, so the Set method must be called three times to release them all. using System; using System.Threading; // Visual Studio: Replace the default class in a Console project with // the following class. class Example { private static AutoResetEvent event_1 = new AutoResetEvent(true); // Created in the signaled state. 立刻執行不等待. private static AutoResetEvent event_2 = new AutoResetEvent(false); static void Main() { Console.WriteLine("Press Enter to create three threads and start them.\r\n" + "The threads wait on AutoResetEvent #1, which was created\r\n" + "in the signaled state, so the first thread is released.\r\n" + "This puts AutoResetEvent #1 into the unsignaled state."); Console.ReadLine(); for (int i = 1; i < 4; i++) { Thread t = new Thread(ThreadProc); t.Name = "Thread_" + i; t.Start(); } Thread.Sleep(250); for (int i = 0; i < 2; i++) { Console.WriteLine("Press Enter to release another thread."); Console.ReadLine(); event_1.Set(); Thread.Sleep(250); } Console.WriteLine("\r\nAll threads are now waiting on AutoResetEvent #2."); for (int i = 0; i < 3; i++) { Console.WriteLine("Press Enter to release a thread."); Console.ReadLine(); event_2.Set(); Thread.Sleep(250); } // Visual Studio: Uncomment the following line. //Console.Readline(); } static void ThreadProc() { string name = Thread.CurrentThread.Name; Console.WriteLine("{0} waits on AutoResetEvent #1.", name); event_1.WaitOne(); Console.WriteLine("{0} is released from AutoResetEvent #1.", name); Console.WriteLine("{0} waits on AutoResetEvent #2.", name); event_2.WaitOne(); Console.WriteLine("{0} is released from AutoResetEvent #2.", name); Console.WriteLine("{0} ends.", name); } } /* This example produces output similar to the following: Press Enter to create three threads and start them. The threads wait on AutoResetEvent #1, which was created in the signaled state, so the first thread is released. This puts AutoResetEvent #1 into the unsignaled state. Thread_1 waits on AutoResetEvent #1. Thread_1 is released from AutoResetEvent #1. Thread_1 waits on AutoResetEvent #2. Thread_3 waits on AutoResetEvent #1. Thread_2 waits on AutoResetEvent #1. Press Enter to release another thread. Thread_3 is released from AutoResetEvent #1. Thread_3 waits on AutoResetEvent #2. Press Enter to release another thread. Thread_2 is released from AutoResetEvent #1. Thread_2 waits on AutoResetEvent #2. All threads are now waiting on AutoResetEvent #2. Press Enter to release a thread. Thread_2 is released from AutoResetEvent #2. Thread_2 ends. Press Enter to release a thread. Thread_1 is released from AutoResetEvent #2. Thread_1 ends. Press Enter to release a thread. Thread_3 is released from AutoResetEvent #2. Thread_3 ends. */ Remarks You use AutoResetEvent, ManualResetEvent, and EventWaitHandle for thread interaction (or thread signaling). For more information, see the Thread interaction, or signaling section of the Overview of synchronization primitives article. A thread waits for a signal by calling AutoResetEvent.WaitOne. If the AutoResetEvent is in the non-signaled state, the thread blocks until AutoResetEvent.Set is called. Calling Set signals AutoResetEvent to release a waiting thread. AutoResetEvent remains signaled until a single waiting thread is released, and then automatically returns to the non-signaled state. If no threads are waiting, the state remains signaled indefinitely. If a thread calls WaitOne while the AutoResetEvent is in the signaled state, the thread does not block. The AutoResetEvent releases the thread immediately and returns to the non-signaled state. #### 2023-12-31 之前的舊資料, 確認後移到上面 AutoResetEvent.txt ---------- 2019-07-25 AutoResetEvent 執行緒同步處理事件: 可控制執行緒的執行順序. AutoResetEvent 物件, 可透過 WaitOne() 中斷執行緒, 等待 Set() 發出信號後, 繼續執行執行緒. 使用方式: 1. 宣告 AutoResetEvent() 物件 Represents a thread synchronization event that, when signaled, must be reset manually. This class cannot be inherited. AutoResetEvent event_1 = new AutoResetEvent(false); // 預設未收到信號, 碰到第一個 WaitOne() 會鎖定執行緒. AutoResetEvent eventT = new AutoResetEvent(true); // 預設已收到信號. 即碰到第一個 WaitOne() 會跳過, 不會鎖定執行緒. AutoResetEvent 物件在已收到信號狀態下, 則 WaitOne() 指令不會鎖定執行緒, 會繼續執行. 2. 等待. WaitOne() 鎖定執行緒, 並等待收到信號後, 再繼續執行執行緒. Blocks the current thread until the current WaitHandle receives a signal. event_1.WaitOne(); // 鎖定執行緒, 等待收到信號後再繼續執行. event_1.WaitOne(milliseconsTimeout); // 等待 milliseconds, 或 (-1)永久等待. 3. Set() 通知 WaitOne() 可繼續執行. Sets the state of the event to signaled, allowing one or more waiting threads to proceed. 4. Reset() 重設. Sets the state of the event to nonsignaled, causing threads to block. 範例: public static ManualResetEvent allDone = new ManualResetEvent(false); while (true) { // Set the event to nonsignaled state. allDone.Reset(); // Start an asynchronous socket to listen for connections. Console.WriteLine("Waiting for a connection..."); listener.BeginAccept(new AsyncCallback(AcceptCallback), listener); // Wait until a connection is made before continuing. allDone.WaitOne(); } public void AcceptCallback(IAsyncResult ar) { // Signal the main thread to continue. allDone.Set(); ... } 樣本: The following example uses an AutoResetEvent to synchronize the activities of two threads. The first thread, which is the application thread, executes Main. It writes values to the protected resource, which is a static (Shared in Visual Basic) field named number. The second thread executes the static ThreadProc method, which reads the values written by Main. The ThreadProc method waits for the AutoResetEvent. When Main calls the Set method on the AutoResetEvent, the ThreadProc method reads one value. The AutoResetEvent immediately resets, so the ThreadProc method waits again. The program logic guarantees that the ThreadProc method will never read the same value two times. It does not guarantee that the ThreadProc method will read every value written by Main. That guarantee would require a second AutoResetEvent lock. After each write operation, Main yields by calling the Thread.Sleep method, to give the second thread a chance to execute. Otherwise, on a single-processor computer Main would write many values between any two read operations. 下列範例會使用AutoResetEvent來同步處理兩個執行緒的活動。 第一個執行緒，也就是應用程式執行緒，執行Main。 它會將值寫入受保護的資源，亦即static(Shared Visual Basic 中) 名為欄位number。 第二個執行緒執行靜態ThreadProc方法，它會讀取寫入的值Main。 ThreadProc方法會等候AutoResetEvent。 當Main呼叫Set方法AutoResetEvent，則ThreadProc方法會讀取一個值。 AutoResetEvent立即重設，所以ThreadProc方法會等候一次。 程式邏輯會保證ThreadProc方法將永遠不會讀取相同的值兩次。 它不保證ThreadProc方法會讀取寫入的每個值Main。 這項保證會需要第二個AutoResetEvent鎖定。 每個寫入作業之後，Main藉由呼叫會產生Thread.Sleep方法，以讓第二個執行緒有機會執行。 否則，在單一處理器電腦上Main可以用來撰寫兩個讀取作業的許多任何之間的值。 using System; using System.Threading; namespace AutoResetEvent_Examples { class MyMainClass { //Initially not signaled. const int numIterations = 100; static AutoResetEvent myResetEvent = new AutoResetEvent(false); // 宣告 AutoResetEvent, 初始狀態未收到訊號 static int number; // 受保護資源. static void Main() { //Create and start the reader thread. Thread myReaderThread = new Thread(new ThreadStart(MyReadThreadProc)); // 子執行緒. myReaderThread.Name = "ReaderThread"; myReaderThread.Start(); for(int i = 1; i <= numIterations; i++) { Console.WriteLine("Writer thread writing value: {0}", i); number = i; // 主執行緒寫入資源 number. //Signal that a value has been written. myResetEvent.Set(); // 通知 WaitOne() 處可繼續執行. //Give the Reader thread an opportunity to act. Thread.Sleep(1); // 給子執行緒機會執行. } //Terminate the reader thread. myReaderThread.Abort(); // 停止子執行緒執行. } static void MyReadThreadProc() { while(true) { //The value will not be read until the writer has written // at least once since the last read. myResetEvent.WaitOne(); // 等待收到訊號後, 再繼續執行子執行緒. Console.WriteLine("{0} reading value: {1}", Thread.CurrentThread.Name, number); // 只讀取資源, 不可寫入. 注意這裡顯示的次數, 未必等於 主執行緒中的迴圈次數. } } } } ---------- AutoResetEvent 在 class instance 中控制最多 5個 thread 同時執行範例: https://stackoverflow.com/questions/3288307/problem-synchronizing-with-manualresetevent public class Downloader { private int fileCount = 0; private AutoResetEvent sync = new AutoResetEvent(false); // 本 Class intance 中控制等待的 AutoResetEvent 物件 private void StartNewDownload(object o) // 每個 Thread 呼叫本函數, 傳入 object o { if (Interlocked.Increment(ref this.fileCount) > 5) this.sync.WaitOne(); // filecount++, 若同時執行中的 thread 超過 5個, 則等待封鎖. WebClient downloadClient = new WebClient(); downloadClient.OpenReadCompleted += downloadClient_OpenReadCompleted; // WebClient 完成時, 呼叫downloadClient_OpenReadCompleted() downloadClient.OpenReadAsync(new Uri(o.ToString(), UriKind.Absolute)); // WebClient 開始執行. } private void downloadClient_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e) { try { // Download logic goes here. // WebClient 完成後的邏輯在這裡處理, 例如另存新檔. } catch {} finally // 不管成功或失敗結果都要執行 { this.sync.Set(); // 解除等待封鎖 Interlocked.Decrement(ref this.fileCount); // fileCount--, } } public void Run() { string o = "url1"; System.Threading.ThreadPool.QueueUserWorkItem(this.StartNewDownload, o); // 交由 ThreadPool.QueueUserWorkItem 以新 thread 執行 StartNewDownload(o="url1") Thread.Sleep(100); o = "url2"; System.Threading.ThreadPool.QueueUserWorkItem(this.StartNewDownload, o); // 交由 ThreadPool.QueueUserWorkItem 以新 thread 執行 StartNewDownload(o="url2") o = "url3"; System.Threading.ThreadPool.QueueUserWorkItem(this.StartNewDownload, o); // 交由 ThreadPool.QueueUserWorkItem 以新 thread 執行 StartNewDownload(o="url3") Thread.Sleep(200); o = "url4"; System.Threading.ThreadPool.QueueUserWorkItem(this.StartNewDownload, o); o = "url5"; System.Threading.ThreadPool.QueueUserWorkItem(this.StartNewDownload, o); o = "url6"; System.Threading.ThreadPool.QueueUserWorkItem(this.StartNewDownload, o); o = "url7"; System.Threading.ThreadPool.QueueUserWorkItem(this.StartNewDownload, o); Thread.Sleep(200); o = "url8"; System.Threading.ThreadPool.QueueUserWorkItem(this.StartNewDownload, o); Thread.Sleep(400); } } ---------- 2018-08-22 ref: https://dotblogs.com.tw/yc421206/2011/01/05/20609 AutoResetEvent 摘要: Mutual exclusion，縮寫 Mutex: 是一種用於多線程編程中，防止兩條線程同時對同一公共資源（比如全局變量）進行讀寫的機制。 1. 宣告 AutoResetEvent() 物件 private static AutoResetEvent event_1 = new AutoResetEvent(false); // 鎖定 private static AutoResetEvent event_1 = new AutoResetEvent(true); // 解除 Specifying true for initialState creates an AutoResetEvent in the signaled state. This is useful if you want the first thread that waits for the AutoResetEvent to be released immediately, without blocking." 參數true/false表示是否已收到信號signal 解除鎖定執行 ? false = 鎖定執行狀態. (signal=false未收到信號通知解除鎖定) true = 解除鎖定執行狀態. (signal=true已收到信號通知解除鎖定) 鎖定執行狀態時, 可利用WaitOne()停止程式繼續執行, 利用Set()通知程式繼續執行. Notifies a waiting thread that an event has occurred. Parameter is a Boolean value indicating whether to set the initial state to signaled. 2. event_1.WaitOne(); // 鎖定執行. event_1.WaitOne(milliseconsTimeout); // The number of milliseconds to wait, or Infinite (-1) to wait indefinitely. 3. event_1.Set(); // 解除鎖定執行. 發出訊號signal, 通知WaitOne()繼續執行, 並自動恢復為鎖定執行狀態. 4. ManualResetEvent() 物件 同AutoResetEvent物件的用法, 都是衍生自EventWaitHandle類別. AutoResetEvent = EventResetMode.AutoReset. ManualResetEvent = EventResetMode.ManualReset. 差別1: 需呼叫Reset()方法, 才能恢復成鎖定執行狀態未收到信號signal狀態. 差別2: AutoResetEvent 一次只能喚醒一個執行緒，ManualResetEvent可以喚醒多個執行緒. 差別3: ManualResetEvent，使用WaitOne鎖定後，必須要再呼叫Reset方法，使其回到未鎖定狀態； AutoResetEvent 就不必呼叫Reset方法，會自動的回到未鎖定狀態。 event_1.Reset(); 1. 宣告 AutoResetEvent() 物件 = false. 2. 呼叫 ref: https://dotblogs.com.tw/yc421206/2011/01/05/20609 這兩個類別AutoResetEvent 類別、ManualResetEvent 類別的WaitOne方法可以使執行緒進入Blocks變成WaitSleepJoin狀態，Set方法可以進入Waitting回到Running狀態。 所以我們可以用它們來等候其他的執行緒進而達到資料同步機制，而他們兩個的用法很像， 1.當使用Set方法後AutoResetEvent會自動處於未收到信號的狀態，而ManualResetEvent必須要再呼叫Reset方法後才會處於未收到信號的狀態。 2.AutoResetEvent 與 ManualResetEvent 是衍生自新的 EventWaitHandle 類別，AutoResetEvent 的功能相等於以 EventResetMode.AutoReset 。ManualResetEvent 的功能等於以 EventResetMode.ManualReset。 3.AutoResetEvent 一次只能喚醒一個執行緒，ManualResetEvent可以喚醒多個執行緒 4.ManualResetEvent，使用WaitOne鎖定後，必須要再呼叫Reset方法，使其回到未鎖定狀態；AutoResetEvent 就不必呼叫Reset方法，會自動的回到未鎖定狀態。 Auto​Reset​Event(Boolean) Initializes a new instance of the AutoResetEvent class with a Boolean value indicating whether to set the initial state to signaled. WaitOne() Blocks the current thread until the current WaitHandle receives a signal. The following code example shows how to use a wait handle to keep a process from terminating while it waits for a background thread to finish executing. using System; using System.Threading; class WaitOne { // 1. 宣告 AutoResetEvent 物件, 參數=false表示接受訊號. static AutoResetEvent autoEvent = new AutoResetEvent(false); // 宣告 AutoResetEvent static void Main() { Console.WriteLine("Main starting."); // 2. 建立Thread, 並傳入 AutoResetEvent 物件. ThreadPool.QueueUserWorkItem(new WaitCallback(WorkMethod), autoEvent); // 將 AutoResetEvent 物件傳入 // Wait for work method to signal. // 3. WaitOne() 停止執行 thread, 直到被 Set() 喚醒. autoEvent.WaitOne(); Console.WriteLine("Work method signaled.\nMain ending."); } static void WorkMethod(object stateInfo) { Console.WriteLine("Work starting."); // Simulate time spent working. Thread.Sleep(new Random().Next(100, 2000)); // Signal that work is finished. Console.WriteLine("Work ending."); // 4. Set() 通知暫停執行的thread 可繼續執行. ((AutoResetEvent)stateInfo).Set(); } } ---------- 20180113 AutoResetEvent ---------- AutoResetEvent allows threads to communicate with each other by signaling. Typically, you use this class when threads need exclusive access to a resource. A thread waits for a signal by calling WaitOne on the AutoResetEvent. If the AutoResetEvent is in the non-signaled state, the thread blocks, waiting for the thread that currently controls the resource to signal that the resource is available by calling Set. Calling Set signals AutoResetEvent to release a waiting thread. AutoResetEvent remains signaled until a single waiting thread is released, and then automatically returns to the non-signaled state. If no threads are waiting, the state remains signaled indefinitely. If a thread calls WaitOne while the AutoResetEvent is in the signaled state, the thread does not block. The AutoResetEvent releases the thread immediately and returns to the non-signaled state. ---------- Example: The following example shows how to use AutoResetEvent to release one thread at a time, by calling the Set method (on the base class) each time the user presses the Enter key. The example starts three threads, which wait on an AutoResetEvent that was created in the signaled state. The first thread is released immediately, because the AutoResetEvent is already in the signaled state. This resets the AutoResetEvent to the non-signaled state, so that subsequent threads block. The blocked threads are not released until the user releases them one at a time by pressing the Enter key. After the threads are released from the first AutoResetEvent, they wait on another AutoResetEvent that was created in the non-signaled state. All three threads block, so the Set method must be called three times to release them all. using System; using System.Threading; // Visual Studio: Replace the default class in a Console project with // the following class. class Example { // true to set the initial state to signaled; false to set the initial state to non-signaled private static AutoResetEvent event_1 = new AutoResetEvent(true); // true表示一開始不 private static AutoResetEvent event_2 = new AutoResetEvent(false); static void Main() { Console.WriteLine("Press Enter to create three threads and start them.\r\n" + "The threads wait on AutoResetEvent #1, which was created\r\n" + "in the signaled state, so the first thread is released.\r\n" + "This puts AutoResetEvent #1 into the unsignaled state."); Console.ReadLine(); for (int i = 1; i < 4; i++) { Thread t = new Thread(ThreadProc); t.Name = "Thread_" + i; t.Start(); } Thread.Sleep(250); for (int i = 0; i < 2; i++) { Console.WriteLine("Press Enter to release another thread."); Console.ReadLine(); event_1.Set(); Thread.Sleep(250); } Console.WriteLine("\r\nAll threads are now waiting on AutoResetEvent #2."); for (int i = 0; i < 3; i++) { Console.WriteLine("Press Enter to release a thread."); Console.ReadLine(); event_2.Set(); Thread.Sleep(250); } // Visual Studio: Uncomment the following line. //Console.Readline(); } static void ThreadProc() { string name = Thread.CurrentThread.Name; Console.WriteLine("{0} waits on AutoResetEvent #1.", name); event_1.WaitOne(); Console.WriteLine("{0} is released from AutoResetEvent #1.", name); Console.WriteLine("{0} waits on AutoResetEvent #2.", name); event_2.WaitOne(); Console.WriteLine("{0} is released from AutoResetEvent #2.", name); Console.WriteLine("{0} ends.", name); } } /* This example produces output similar to the following: Press Enter to create three threads and start them. The threads wait on AutoResetEvent #1, which was created in the signaled state, so the first thread is released. This puts AutoResetEvent #1 into the unsignaled state. Thread_1 waits on AutoResetEvent #1. Thread_1 is released from AutoResetEvent #1. Thread_1 waits on AutoResetEvent #2. Thread_3 waits on AutoResetEvent #1. Thread_2 waits on AutoResetEvent #1. Press Enter to release another thread. Thread_3 is released from AutoResetEvent #1. Thread_3 waits on AutoResetEvent #2. Press Enter to release another thread. Thread_2 is released from AutoResetEvent #1. Thread_2 waits on AutoResetEvent #2. All threads are now waiting on AutoResetEvent #2. Press Enter to release a thread. Thread_2 is released from AutoResetEvent #2. Thread_2 ends. Press Enter to release a thread. Thread_1 is released from AutoResetEvent #2. Thread_1 ends. Press Enter to release a thread. Thread_3 is released from AutoResetEvent #2. Thread_3 ends. */