From: 011netservice@gmail.com Date: 2022-04-24 Subject: Invoke.txt public IAsyncResult BeginInvoke(Delegate method); public IAsyncResult BeginInvoke(Delegate method, params object[] args); public object Invoke(Delegate method); public object Invoke(Delegate method, params object[] args); ---------- 20210124 Invoke方法會順著控制元件樹向上搜尋，直到找到建立控制元件的那個執行緒（通常是主執行緒）， 然後進入那個執行緒改變控制元件的外觀，確保不發生執行緒衝突。 public delegate void KeyDownF5EventHandler(); public event KeyDownF5EventHandler OnKeyDownF5; private void FBase1_KeyDown(object sender, KeyEventArgs e) { //if (e.KeyCode == Keys.F5 && btnRun.Enabled) //{ // BtnRun_Click(btnRun, EventArgs.Empty); //} // Delegate invocation can be simplified. //if (e.KeyCode == Keys.F5) // if (OnF5 != null) // OnF5(); if (e.KeyCode == Keys.F5) OnKeyDownF5?.Invoke(); } ---------- 20201106 public delegate void InvokeDelegate(); private void Invoke_Click(object sender, EventArgs e) { myTextBox.BeginInvoke(new InvokeDelegate(InvokeMethod)); } public void InvokeMethod() { myTextBox.Text = "Executed the given delegate"; } ---------- 20201106 public static void ZInvokeSetText(this Control ctrl, string sText) { ZInvokeAction(ctrl, () => ctrl.Text = sText); // CodeHelper: Lambda. } public static void ZInvokeAction(this Control control, Action action) { // Executes the Action asynchronously on the UI thread, does not block execution on the calling thread. // this.InvokeOnUiThreadIfRequired(() => urlTextBox.Text = args.Address); if (control.InvokeRequired) { control.BeginInvoke(action); } else { action.Invoke(); } } /// ZInvokeAction(ctrl, () => ctrl.Text = sText); /// 或 ZInvokeAction(ctrl, () => {statement1; statement2;...}); ---------- 20201106 void im_UserAvailable(object sender, IMAvailEventArgs e) { this.BeginInvoke(new MethodInvoker(delegate { if (e.UserName == sendTo) { if (lastAvail != e.IsAvailable) { lastAvail = e.IsAvailable; string avail = (e.IsAvailable ? "available" : "unavailable"); this.Text = String.Format("{0} - {1}", sendTo, avail); talkText.Text += String.Format("[{0} is {1}]\r\n", sendTo, avail); } } })); } ---------- 20201106 InvokeRequired, Invoke 1 InvokeRequired 原本以 delegate 的寫法較繁雜: delegate void ShowMsgCallback(string sMsg); public virtual void ShowMsg(string sMsg) { if (statusStrip1.InvokeRequired) // Sample: InvokeRequired. Invoke(new ShowMsgCallback(MyShowMsg), new Object[] { sMsg }); // Sample: Invoke() else MyShowMsg(sMsg); } void MyShowMsg(string sMsg) { lblMsg.ForeColor = ColorSaved; lblMsg.Text = sMsg; } 2 InvokeRequired 改為 Lambda 運算式寫法, 可取代 (1 delegate 的寫法), 較簡潔, 且不影響效能. private void MThread_OnError(string sType, string sError, ZThreadState State1) { if (LblEndTime.InvokeRequired) LblEndTime.Invoke(new Action(() => { LblTime.Text = sError; })); else LblTime.Text = sError; } 以 Form.Invoke 的參考樣式: private void MThread_OnStart(ZThreadState state1) { while (true) { if (InvokeRequired) { Invoke(new Action(() => { LblTime.Text = DateTime.Now.ToString(); LblEndTime.Text = MThread.EndTime.ToString(); })); } else { LblTime.Text = DateTime.Now.ToString(); LblEndTime.Text = MThread.EndTime.ToString(); } ZThreading.ZSleep(1000); } } */ using System; using System.Collections.Generic; using System.Linq; using System.Text; // add using System.Threading.Tasks; using System.Threading; namespace ZLib.DSample { class LambdaSample { event Action OnAction; event Action OnAction1Input; class cItem1 { public int _i1; public string _s1; } void LinqVsLambda1() { int iCount; int iSum; int[] ia1 = { 1, 3, 5, 7, 9 }; List list1 = new List(); list1.Add(new cItem1() { _i1 = 1, _s1 = "a" }); list1.Add(new cItem1() { _i1 = 3, _s1 = "b" }); list1.Add(new cItem1() { _i1 = 5, _s1 = "c" }); list1.Add(new cItem1() { _i1 = 7, _s1 = "a" }); list1.Add(new cItem1() { _i1 = 9, _s1 = "b" }); // linq = Language Integrated Query // Visual Studio 提供(能以類似 SQL 語法查詢)的功能. // 較具可讀性. iCount = (from p1 in ia1 where p1 > 5 select p1).Count(); // 2 iSum = (from p1 in ia1 where p1 > 5 select p1).Sum(); // 16 var vLinq1 = from p1 in list1 // _s1="a"的清單=2筆. where p1._s1 == "a" select p1; List listLinq1 = (from p1 in list1 // _s1="a"的清單=2筆. where p1._s1 == "a" select p1).ToList(); iCount = (from p1 in list1 // _s1="a"的個數=2. where p1._s1 == "a" select p1).Count(); iSum = (from p1 in list1 // sum((_s1="a"的項目).i1) = 8. where p1._s1 == "a" select p1._i1).Sum(); // lambda = an anonymous function and is more of a like delegate type. // 代表一個匿名函數, 比較像一個 delegate. // 運算式中有一個 "=>" 運算符號, 讀為 "goes to". // 運算式左邊為輸入的參數. // 較簡潔, 可用一行指令就完成. iCount = ia1.Where(p1 => p1 > 5).Count(); // 2 iSum = ia1.Where(p1 => p1 > 5).Sum(); // 16 var vLambda1 = list1.Where(p1 => p1._s1 == "a"); // _s1="a"的清單=2筆. List listLambda1 = list1.Where(p1 => p1._s1 == "a").ToList(); // _s1 = "a"的清單 = 2筆. // 轉成其他型別 List listia1 = ia1.Where(p1 => p1 > 5).ToList(); List listda1 = listia1.ConvertAll(IntToDouble); } double IntToDouble(int iInput) { return iInput; } void SampleThread() { Thread t1; Thread t2; string sResult; // .net 的寫法: t1 = new Thread(new ThreadStart(MyMethod1)); t1.Start(); t2 = new Thread(new ParameterizedThreadStart(MyMethod2)); t2.Start("Parameter"); // Lambda 的寫法: t1 = new Thread(() => { sResult = "Lambda1"; }); t1.Start(); t2 = new Thread((state) => { sResult = state.ToString(); }); t2.Start(); ThreadPool.QueueUserWorkItem(arg => MyMethod1()); ThreadPool.QueueUserWorkItem(arg => { MyMethod1(); }); ThreadPool.QueueUserWorkItem(arg => MyMethod2(arg)); ThreadPool.QueueUserWorkItem(arg => { MyMethod2(arg); }); // ZLib 的寫法: t1 = ZThreading.ZStart(MyMethod1); t2 = ZThreading.ZStart(MyMethod2, "With State"); } void MyMethod1() { Console.WriteLine($"MyMethod1(), ThreadID={ZThreading.ZGetCurrentThreadID()}"); } void MyMethod2(object State) { Console.WriteLine($"MyMethod2(), {State.ToString()}, ThreadID={ZThreading.ZGetCurrentThreadID()}"); } void SampleWhere1() { // form o in SomeList where o.Col1 == "A" && o.Col2 == "B" select o int[] ia1 = { 1, 3, 5, 7, 9 }; int iCount = (from number in ia1 where number > 5 select number).Count(); // 2 int iSum = (from number in ia1 where number > 5 select number).Sum(); // 16 } void SampleFunc2String() { // Declare a Func variable and assign a lambda expression to the // variable. The method takes a string and converts it to uppercase. Func selector = str => str.ToUpper(); // Create an array of strings. string[] words = { "orange", "apple", "Article", "elephant" }; // Query the array and select strings according to the selector method. IEnumerable aWords = words.Select(selector); // Output the results to the console. foreach (String word in aWords) Console.WriteLine(word); /* This code example produces the following output: ORANGE APPLE ARTICLE ELEPHANT */ } async Task AsyncTask2(string sInput) { // 呼叫一個 Task.Run(Action) await Task.Run(() => myBlockingMethod(sInput)); } async Task AsyncTask3(string sInput) { // 呼叫一個 Task.Run(Action)傳入一個物件參數! 不是字串參數, 字串會轉為object傳入 Task.Run. return await Task.Run(() => { return myBlockingMethod(sInput); }); } void StartByLambda2() { OnAction += async () => await myOnStartTask(); } Task StartByLambda3() { Task t1 = null; OnAction += async () => await (t1 = myOnStartTask()); return t1; } Task asyncByLambda4(string sInput) { Task t1 = null; OnAction1Input += async (p1) => await (t1 = myBlockingTask(p1)); //OnAction1Input += async (p1) => await (Task < string > t1 = myBlockingTask(p1)); return t1; } string myBlockingMethod(string sInput) { ZThreading.ZSleep(2000); return "myBlockingMethod()+" + sInput; } Task myOnStartTask() { Task t1 = Task.Run(() => { myOnStart(); }); return t1; } private void myOnStart() { if (OnAction != null) OnAction(); if (OnAction1Input != null) OnAction1Input("解除warning"); } private Task myBlockingTask(string sInput) { Task t1 = Task.Run(() => { return myBlockingMethod(sInput); }); return t1; } } } ---------- 20201106 invoke vs BeginInvoke https://stackoverflow.com/questions/229554/whats-the-difference-between-invoke-and-begininvoke Do you mean Delegate.Invoke/BeginInvoke or Control.Invoke/BeginInvoke? Delegate.Invoke: Executes synchronously, on the same thread. Delegate.BeginInvoke: Executes asynchronously, on a threadpool thread. Control.Invoke: Executes on the UI thread, but calling thread waits for completion before continuing. Control.BeginInvoke: Executes on the UI thread, and calling thread doesn't wait for completion. Tim's answer mentions when you might want to use BeginInvoke - although it was mostly geared towards Delegate.BeginInvoke, I suspect. For Windows Forms apps, I would suggest that you should usually use BeginInvoke. That way you don't need to worry about deadlock, for example - but you need to understand that the UI may not have been updated by the time you next look at it! In particular, you shouldn't modify data which the UI thread might be about to use for display purposes. For example, if you have a Person with FirstName and LastName properties, and you did: person.FirstName = "Kevin"; // person is a shared reference person.LastName = "Spacey"; control.BeginInvoke(UpdateName); person.FirstName = "Keyser"; person.LastName = "Soze"; Then the UI may well end up displaying "Keyser Spacey". (There's an outside chance it could display "Kevin Soze" but only through the weirdness of the memory model.) Unless you have this sort of issue, however, Control.BeginInvoke is easier to get right, and will avoid your background thread from having to wait for no good reason. Note that the Windows Forms team has guaranteed that you can use Control.BeginInvoke in a "fire and forget" manner - i.e. without ever calling EndInvoke. This is not true of async calls in general: normally every BeginXXX should have a corresponding EndXXX call, usually in the callback.