WorkflowInvoker.CancelAsync(Object) Method

Reference

Definition

Namespace:: System.Activities

Assembly:: System.Activities.dll

Important

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Attempts to cancel the workflow that was invoked with the specified userState.

public:
 void CancelAsync(System::Object ^ userState);

public void CancelAsync (object userState);

member this.CancelAsync : obj -> unit

Public Sub CancelAsync (userState As Object)

Parameters

userState: Object

The token for the workflow to cancel.

Examples

The following example invokes a workflow consisting of a LongRunningDiceRoll activity. The LongRunningDiceRoll activity has two output arguments that represent the results of the dice roll operation. Once the workflow is invoked, the host attempts to cancel the workflow.

public sealed class LongRunningDiceRoll : Activity
{
    public OutArgument<int> D1 { get; set; }
    public OutArgument<int> D2 { get; set; }

    public LongRunningDiceRoll()
    {
        this.Implementation = () => new Sequence
        {
            Activities =
            {
                new WriteLine
                {
                    Text = "Rolling the dice for 5 seconds."
                },
                new Delay
                {
                    Duration = TimeSpan.FromSeconds(5)
                },
                new DiceRoll
                {
                    D1 = new OutArgument<int>(env => this.D1.Get(env)),
                    D2 = new OutArgument<int>(env => this.D2.Get(env))
                }
            }
        };
    }
}

AutoResetEvent syncEvent = new AutoResetEvent(false);

WorkflowInvoker invoker = new WorkflowInvoker(new LongRunningDiceRoll());

invoker.InvokeCompleted += delegate(object sender, InvokeCompletedEventArgs args)
{
    if (args.Cancelled)
    {
        Console.WriteLine("The workflow was cancelled.");
    }
    else if (args.Error != null)
    {
        Console.WriteLine("Exception: {0}\n{1}",
            args.Error.GetType().FullName,
            args.Error.Message);
    }
    else
    {
        Console.WriteLine("The two dice are {0} and {1}.",
            args.Outputs["D1"], args.Outputs["D2"]);
    }

    syncEvent.Set();
};

string userState = "CancelAsync Example";
invoker.InvokeAsync(userState);

Console.WriteLine("Waiting for the workflow to complete.");
Thread.Sleep(TimeSpan.FromSeconds(1));

Console.WriteLine("Attempting to cancel the workflow.");
invoker.CancelAsync(userState);

// Wait for the workflow to complete.
syncEvent.WaitOne();

Console.WriteLine("The workflow is either completed or cancelled.");

Remarks

Only a workflow invoked by one of the InvokeAsync overloads that takes a userState parameter can be canceled.

If the cancellation succeeds, the Cancelled property of the InvokeCompletedEventArgs passed to the InvokeCompleted handler is set to true; otherwise, it is set to false.

Applies to

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