C#中的异步多线程9 完整的GUI示例

MainWindow.xaml.cs

    public partial class MainWindow : Window
    {
        //CancellationTokenSource用于创建可分配给不同任务的CancellationToken对象。任何持有CancellationTokenSource的对象都可以调用其Cancel方法，从而
        //将CancellationToken的IsCancellationRequested设置为true
        CancellationTokenSource cts;
        //CancellationToken包含一个任务是否应该被取消的消息，拥有CancellationToken的对象会定期检查其持有的token状态，如果CancellationToken的
        //IsCancellationRequested属性为true，就会取消任务执行。
        CancellationToken ct;
        
        public MainWindow()
        {
            InitializeComponent();
        }

        private async void btnProcess_Click(object sender, RoutedEventArgs e)
        {
            btnProcess.IsEnabled = false;
            cts = new CancellationTokenSource();
            //为ct分发token
            ct = cts.Token;
            int completedPercent = 0;
            for(int i=0;i<10;i++)
            {
                //如果ct.IsCancellationRequested==true，那么任务会被取消
                if (ct.IsCancellationRequested)
                    break;
                try
                {
                    //Task.Delay不会阻塞线程，也就是执行到这里时，异步等待0.5s，但控制权会交还给消息泵执行下一个动作
                    await Task.Delay(500, ct);
                    completedPercent = (i + 1) * 10;
                }
                catch(TaskCanceledException ex)
                {
                    completedPercent = i * 10;
                }
                processBar.Value = completedPercent;
            }
            string message = ct.IsCancellationRequested ? string.Format("Process was cancelled at {0}%.", completedPercent) : "Process completed normally";
            MessageBox.Show(message, "Completion Status");
            processBar.Value = 0;
            btnProcess.IsEnabled = true;
            btnCancel.IsEnabled = true;
        }

        private void btnCancel_Click(object sender, RoutedEventArgs e)
        {
            if(!btnProcess.IsEnabled)
            {
                btnCancel.IsEnabled = false;
                cts.Cancel();
            }
        }
    }

MainWindows.xaml

    <StackPanel>
        <Button Name="btnProcess" Width="100" Click="btnProcess_Click" HorizontalAlignment="Right" Margin="10,15,10,10">Process</Button>
        <Button Name="btnCancel" Width="100" Click="btnCancel_Click" HorizontalAlignment="Right" Margin="10,0">Cancel</Button>
        <ProgressBar Name="processBar" Height="20" Width="500" Margin="10" HorizontalAlignment="Right"></ProgressBar>
    </StackPanel>