1         #region Long-Running Calculation in UI Thread
 2 
 3         public delegate void NextPrimeDelegate();
 4         private long num = 3;
 5         private bool continueCalculating = false;
 6         private bool fNotAPrime = false;
 7 
 8         private void btnPrimeNumber_Click(object sender, RoutedEventArgs e)
 9         {
10             if (continueCalculating)
11             {
12                 continueCalculating = false;
13                 btnPrimeNumber.Content = "Resume";
14             }
15             else
16             {
17                 continueCalculating = true;
18                 btnPrimeNumber.Content = "Stop";
19 
20                 //获取与此 System.Windows.Threading.DispatcherObject 关联的 System.Windows.Threading.Dispatcher
21 
22                 //public DispatcherOperation BeginInvoke(DispatcherPriority priority, Delegate method);
23                 //按指定的优先级在与 System.Windows.Threading.Dispatcher 关联的线程上异步执行指定的委托。
24                 btnPrimeNumber.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new NextPrimeDelegate(CheckNextNumber));
25 
26             }
27         }
28 
29         public void CheckNextNumber()
30         {
31             // Reset flag.
32             fNotAPrime = false;
33 
34             for (long i = 3; i <= Math.Sqrt(num); i++)
35             {
36                 if (num % i == 0)
37                 {
38                     // Set not-a-prime flag to true.
39                     fNotAPrime = true;
40                     break;
41                 }
42             }
43 
44             // If a prime number.
45             if (!fNotAPrime)
46             {
47                 tbPrime.Text = num.ToString();
48             }
49 
50             num += 2;
51 
52             if (continueCalculating)
53             {
54                 //3.In the CheckNextNumber function, because the first parameter
55                 //passed into BeginInvoke is DispatcherPriority.SystemIdle(在系统空闲时处理操作。), 
56                 //all of the CheckNextNumber workitem will not break the UI operation.
57 
58                 btnPrimeNumber.Dispatcher.BeginInvoke(
59                     System.Windows.Threading.DispatcherPriority.SystemIdle,
60                     new NextPrimeDelegate(this.CheckNextNumber));
61             }
62         }
63 
64         #endregion

 1   #region Blocking Operation in Worker Thread
 2 
 3         private delegate void NoArgDelegate();
 4         private delegate void OneArgDelegate(Int32[] arg);
 5 
 6         //1.When the Retrieve Data from Server button is clicked, the click handle retrieveData function is called.
 7         private void btnRetrieveData_Click(object sender, RoutedEventArgs e)
 8         {
 9             this.btnRetrieveData.IsEnabled = false;
10             this.btnRetrieveData.Content = "Contacting Server";
11 
12             NoArgDelegate fetcher = new NoArgDelegate(this.RetrieveDataFromServer);
13 
14             //2.Then our codes use delegate.BeginInvoke to start a thread from the thread pool.
15             //This thread is used to perform the long operation of retrieving data.
16             fetcher.BeginInvoke(null, null);
17         }
18 
19         /// <summary>
20         /// Retrieve data in a worker thread(辅助线程).
21         /// </summary>
22         private void RetrieveDataFromServer()
23         {
24             //3.We use Thread.Sleep(5000) to simulate(模拟) a 5 seconds delay here.
25             // Simulate the delay from network access.
26             Thread.Sleep(5000);
27 
28             //4.The codes generate 4 random numbers as data and update them to the UI by calling the Dispatcher.BeginInvoke().
29 
30             // Generate random data to be displayed.
31             Random rand = new Random();
32             Int32[] data = {
33                                rand.Next(1000), rand.Next(1000), 
34                                rand.Next(1000), rand.Next(1000) 
35                            };
36 
37             // Schedule the update function in the UI thread.
38             this.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal,
39                 new OneArgDelegate(UpdateUserInterface),  data);
40               
41         }
42 
43         /// <summary>
44         /// Update the UI about the new data. The function runs in the UI thread.
45         /// </summary>
46         /// <param name="data"></param>
47         private void UpdateUserInterface(Int32[] data)
48         {
49             this.btnRetrieveData.IsEnabled = true;
50             this.btnRetrieveData.Content = "Retrieve Data from Server";
51             this.tbData1.Text = data[0].ToString();
52             this.tbData2.Text = data[1].ToString();
53             this.tbData3.Text = data[2].ToString();
54             this.tbData4.Text = data[3].ToString();
55         }
56 
57         #endregion