WF：检查工作流应用程序是否已从自定义活动中取消

Question

如何从 NativeActivity 检查工作流应用程序的“取消”方法是否被调用？

我尝试使用上下文的“IsCancellationRequested”属性，但作用不大。

这是我的样本：

public class Program
{
    static void Main(string[] args)
    {
        ManualResetEventSlim mre = new ManualResetEventSlim(false);
        WorkflowApplication app = new WorkflowApplication(new Sequence() { Activities = {new tempActivity(), new tempActivity() } });
        app.Completed += delegate(WorkflowApplicationCompletedEventArgs e)
        {
            mre.Set();
        };
        app.Run(TimeSpan.MaxValue);
        Thread.Sleep(2000);
        app.BeginCancel(null,null);
        mre.Wait();
    }
}

public class tempActivity : NativeActivity
{
    protected override void Execute(NativeActivityContext context)
    {
        Console.WriteLine("Exec tempActivity");
        for (int i = 0; i < 10; i++)
        {
            Thread.Sleep(1000);
            Console.Write(".");
            if (context.IsCancellationRequested)
                return;
        }
    }
}

谢谢！

Answer 1

工作流程中的几乎所有内容都是异步调度和执行的。这包括取消，因此执行中的阻塞可确保取消请求永远不会被处理。

您需要像这样编写活动：

public class tempActivity : NativeActivity
{
    private Activity Delay { get; set; }
    private Variable<int> Counter { get; set; }

    protected override void CacheMetadata(NativeActivityMetadata metadata)
    {
        Counter = new Variable<int>();
        Delay = new Delay() { Duration = TimeSpan.FromSeconds(1) };

        metadata.AddImplementationChild(Delay);
        metadata.AddImplementationVariable(Counter);

        base.CacheMetadata(metadata);
    }


    protected override void Execute(NativeActivityContext context)
    {
        OnCompleted(context, null);
    }

    private void OnCompleted(NativeActivityContext context, ActivityInstance completedInstance)
    {
        var counter = Counter.Get(context);
        if (counter < 10 && !context.IsCancellationRequested)
        {
            Console.Write(".");
            Counter.Set(context, counter + 1);
            context.ScheduleActivity(Delay, OnCompleted);
        }
    }
}