C# Control.Invoke方法－天天向上

Delegate為委派，Invoke表示要呼叫所指定的方法(method)，第二個為傳入參數陣列

MyFormControl繼承Form

1. Line 3: 宣告委派:delegate void AddListItem(String myString)，表示需要傳入一字串無回傳值。

2. Line4: 宣告委派:delegate void ClearListItem()，表示無參數輸入且無回傳值。

3. Line5~6: myAddDelegate和myClearDelegate則為上述兩種委派的物件，目前未實體化。

4. MyFormControl創建子 MyFormControl(){…} 主要在視窗建立myButton和myListBox，利用Controls.AddRange加入控制元件。

5. Line 26: 實體化myAddDelegate委派物件，傳入參數為AddListItemMethod方法名稱，該方法符合委派方法樣板定義(Line 3)。

6. Line 27: 實體化myClearDelegate委派物件，傳入參數為ClearListItemMethod方法名稱，該方法符合委派方法樣板定義(Line 4)。

7. Line 29: 按鈕事件: 執行執行緒ThreadFunction

8. Line 42: 執行緒ThreadFunction方法: 實體化一個MyThreadClass物件，同時將目前MyControlForm物件本身當作引數傳入，接著直接執行myThreadClassObject.Run()方法。

   1: public class MyFormControl:Form   2:    {   3:        public delegate void AddListItem(String myString);   4:        public delegate void ClearListItem();   5:        public AddListItem myAddDelegate;   6:        public ClearListItem myClearDelegate;   7:        private Button myButton;   8:        private Thread myThread;   9:        private ListBox myListBox;  10:        public MyFormControl()  11:        {  12:            myButton = new Button();  13:            myListBox = new ListBox();  14:            myButton.Location = new Point(72, 160);  15:            myButton.Size = new Size(152, 32);  16:            myButton.TabIndex = 1;  17:            myButton.Text = "Add items in list box";  18:            myButton.Click += new EventHandler(Button_Click);  19:            myListBox.Location = new Point(48, 32);  20:            myListBox.Name = "myListBox";  21:            myListBox.Size = new Size(200, 95);  22:            myListBox.TabIndex = 2;  23:            ClientSize = new Size(292, 273);  24:            Controls.AddRange(new Control[] { myListBox, myButton });  25:            Text = " 'Control_Invoke' example ";  26:            myAddDelegate = new AddListItem(AddListItemMethod);  27:            myClearDelegate = new ClearListItem(ClearListItemMethod);  28:        }  29:        private void Button_Click(object sender, EventArgs e)  30:        {  31:            myThread = new Thread(new ThreadStart(ThreadFunction));  32:            myThread.Start();  33:        }  34:        private void AddListItemMethod(String myString)  35:        {  36:            myListBox.Items.Add(myString);  37:        }  38:        private void ClearListItemMethod()  39:        {  40:            myListBox.Items.Clear();  41:        }  42:        private void ThreadFunction()  43:        {  44:            MyThreadClass myThreadClassObject = new MyThreadClass(this);  45:            myThreadClassObject.Run();  46:        }  47:    }

1. MyThreadClass類別中包含一個myFormControl1，這個物件會在MyThreadClass創建子階段(Line 4~7), 由上面一段程式中Line 44傳入this被初始化。

2. if(myFormControl1.InvokeRequired) 判斷目前被呼叫的程式是否屬於相同執行緒，若不同則InvokeRequired為真。

3. 由於ThreadFunction是屬於另外一隻執行緒，與控制元件分屬不同執行緒，因此呼叫必須採用myFormControl1.Invoke(…)方式呼叫，Invoke()參數為委派實體物件，Line15 為myFormControl1.myClearDelegate委派實體

4. Line 21~36 為列印字串 myString，該字串動態變化 “Step number” + i.ToString() + “ executed;

5. 和第3點狀況相同，由於ThreadFunction是屬於另外一隻執行緒，與控制元件分屬不同執行緒，因此呼叫必須採用myFormControl1.Invoke(…)方式呼叫，Invoke()參數為委派實體物件，Line29 為myFormControl1.myAddDelegate委派實體，該委派需同時傳入一組字串，在此以new object[]物件陣列方式傳入

   1: public class MyThreadClass   2:    {   3:        MyFormControl myFormControl1;   4:        public MyThreadClass(MyFormControl myForm)   5:        {   6:            myFormControl1 = myForm;   7:        }   8:        String myString;   9:        public void Run()  10:        {  11:            if(myFormControl1.InvokeRequired)  12:            {  13:                MessageBox.Show("myFormControl1.InvokeRequired");  14:                // invoke 無參數傳入  15:                myFormControl1.Invoke(myFormControl1.myClearDelegate);  16:            }  17:            else  18:            {  19:                myFormControl1.myClearDelegate();  20:            }  21:            for (int i = 1; i <= 5; i++)  22:            {  23:                myString = "Step number " + i.ToString() + " executed";  24:                Thread.Sleep(400);  25:                // Invoke 1參數傳入  26:                if (myFormControl1.InvokeRequired)  27:                {  28:                    //MessageBox.Show("myFormControl1.InvokeRequired");  29:                    myFormControl1.Invoke(myFormControl1.myAddDelegate, new object[] { myString });  30:                }  31:                else  32:                {  33:                    myFormControl1.myAddDelegate(myString);  34:                }  35:            }  36:        }  37:    }