WPF中的多进程(Threading)处理实例(一)

说明：希望通过揣摩这些案例，能进一步了解进程的工作原理。

1.方法一描述的是在同一窗口中，在计算素数的同时而不影响Canvas的工作。

        #region Long-Running Calculation in UI Thread

        public delegate void NextPrimeDelegate();
        private long num = 3;
        private bool continueCalculating = false;
        private bool fNotAPrime = false;

        private void btnPrimeNumber_Click(object sender, RoutedEventArgs e)
        {
            if (continueCalculating)
            {
                continueCalculating = false;
                btnPrimeNumber.Content = "Resume";
            }
            else
            {
                continueCalculating = true;
                btnPrimeNumber.Content = "Stop";

                //获取与此 System.Windows.Threading.DispatcherObject 关联的 System.Windows.Threading.Dispatcher

                //public DispatcherOperation BeginInvoke(DispatcherPriority priority, Delegate method);
                //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。
                btnPrimeNumber.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new NextPrimeDelegate(CheckNextNumber));

            }
        }

        public void CheckNextNumber()
        {
            // Reset flag.
            fNotAPrime = false;

            for (long i = 3; i <= Math.Sqrt(num); i++)
            {
                if (num % i == 0)
                {
                    // Set not-a-prime flag to true.
                    fNotAPrime = true;
                    break;
                }
            }

            // If a prime number.
            if (!fNotAPrime)
            {
                tbPrime.Text = num.ToString();
            }

            num += 2;

            if (continueCalculating)
            {
                //3.In the CheckNextNumber function, because the first parameter
                //passed into BeginInvoke is DispatcherPriority.SystemIdle(在系统空闲时处理操作。), 
                //all of the CheckNextNumber workitem will not break the UI operation.

                btnPrimeNumber.Dispatcher.BeginInvoke(
                    System.Windows.Threading.DispatcherPriority.SystemIdle,
                    new NextPrimeDelegate(this.CheckNextNumber));
            }
        }

        #endregion

  #region Blocking Operation in Worker Thread

        private delegate void NoArgDelegate();
        private delegate void OneArgDelegate(Int32[] arg);

        //1.When the Retrieve Data from Server button is clicked, the click handle retrieveData function is called.
        private void btnRetrieveData_Click(object sender, RoutedEventArgs e)
        {
            this.btnRetrieveData.IsEnabled = false;
            this.btnRetrieveData.Content = "Contacting Server";

            NoArgDelegate fetcher = new NoArgDelegate(this.RetrieveDataFromServer);

            //2.Then our codes use delegate.BeginInvoke to start a thread from the thread pool.
            //This thread is used to perform the long operation of retrieving data.
            fetcher.BeginInvoke(null, null);
        }

        /// <summary>
        /// Retrieve data in a worker thread(辅助线程).
        /// </summary>
        private void RetrieveDataFromServer()
        {
            //3.We use Thread.Sleep(5000) to simulate(模拟) a 5 seconds delay here.
            // Simulate the delay from network access.
            Thread.Sleep(5000);

            //4.The codes generate 4 random numbers as data and update them to the UI by calling the Dispatcher.BeginInvoke().

            // Generate random data to be displayed.
            Random rand = new Random();
            Int32[] data = {
                               rand.Next(1000), rand.Next(1000), 
                               rand.Next(1000), rand.Next(1000) 
                           };

            // Schedule the update function in the UI thread.
            this.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal,
                new OneArgDelegate(UpdateUserInterface),  data);
              
        }

        /// <summary>
        /// Update the UI about the new data. The function runs in the UI thread.
        /// </summary>
        /// <param name="data"></param>
        private void UpdateUserInterface(Int32[] data)
        {
            this.btnRetrieveData.IsEnabled = true;
            this.btnRetrieveData.Content = "Retrieve Data from Server";
            this.tbData1.Text = data[0].ToString();
            this.tbData2.Text = data[1].ToString();
            this.tbData3.Text = data[2].ToString();
            this.tbData4.Text = data[3].ToString();
        }

        #endregion