WorkflowInvoker.BeginInvoke Method (AsyncCallback, Object)

.NET Framework (current version)

Invokes a workflow asynchronously using the specified AsyncCallback and user-provided state.

Namespace:   System.Activities
Assembly:  System.Activities (in System.Activities.dll)

public IAsyncResult BeginInvoke(
	AsyncCallback callback,
	object state


Type: System.AsyncCallback

The method to be called when the workflow has completed.

Type: System.Object

An optional application-specific object that contains information about the asynchronous operation.

Return Value

Type: System.IAsyncResult

A reference to the asynchronous invoke operation.

To be notified when the workflow is complete and retrieve the output parameters of the workflow, call EndInvoke from the callback method. If EndInvoke is called before the workflow completes, it blocks until the workflow completes. To configure a time-out interval in which the workflow must complete, use one of the BeginInvoke overloads that take a TimeSpan.

This method invokes a workflow asynchronously using the IAsyncResult asynchronous design pattern. For more information, seeAsynchronous Programming Overview.

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. These are retrieved by calling EndInvoke. When the call to EndInvoke returns, each output argument is returned in the outputs dictionary, keyed by argument name.

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))
static void BeginInvokeExample()
    WorkflowInvoker invoker = new WorkflowInvoker(new LongRunningDiceRoll());

    string userState = "BeginInvoke example";
    IAsyncResult result = invoker.BeginInvoke(new AsyncCallback(WorkflowCompletedCallback), userState);

    // You can inspect result from the host to determine if the workflow
    // is complete.
    Console.WriteLine("result.IsCompleted: {0}", result.IsCompleted);

    // The results of the workflow are retrieved by calling EndInvoke, which
    // can be called from the callback or from the host. If called from the
    // host, it blocks until the workflow completes. If a callback is not
    // required, pass null for the callback parameter.
    Console.WriteLine("Waiting for the workflow to complete.");
    IDictionary<string, object> outputs = invoker.EndInvoke(result);

    Console.WriteLine("The two dice are {0} and {1}.",
        outputs["D1"], outputs["D2"]);

static void WorkflowCompletedCallback(IAsyncResult result)
    Console.WriteLine("Workflow complete.");

.NET Framework
Available since 4.0
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