Windows Workflow Foundation Activities

Article
03/05/2010

Windows Workflow Foundation (WF) includes a default set of activities that provide functionality for control flow, conditions, event handling, state management, and communicating with applications and services. When you design workflows, you can use the activities that are provided by Windows Workflow Foundation, and you can create your own custom activities.

Activities are the fundamental building blocks of workflows. A workflow is a set of activities that are organized hierarchically in a tree structure. An activity represents an action in a workflow. It can be a simple action such as a delay, or it can be a composite activity that consists of several child activities.

An activity, like a workflow, can be sequential, which means that the order of its actions is specified at design time. Or the activity can be event-driven, which means that the order of its actions is determined at run time in response to external events.

Every activity has an activity execution context that represents the execution environment of the activity. An activity execution context is similar to an HTTP context in that an object has a state, a set of parameters, and constructs that are unique to that given object for that given point in time. Certain composite activities, such as ReplicatorActivity activities and WhileActivity activities, create multiple instances of their child activities during execution, and each child activity has its own activity execution context that it runs in. For more information about activity execution contexts, see Understanding the Activity Execution Context.

Every activity also transitions through various states during its lifetime. Some transitions are controlled by the workflow runtime engine, while others can be user-controlled, such as transitioning a child activity from Executing to Closed. For more information about activity states, see Understanding the Activity State Model.

The following table lists the activities in the Windows Workflow Foundation base activity library.

Activity	Description
CallExternalMethodActivity	Used with the HandleExternalEventActivity activity for input and output communications with a local service. For more information, see Using the CallExternalMethodActivity Activity.
CancellationHandlerActivity	Used to contain cleanup logic for a composite activity that is canceled before all the composite activity's child activities are finished executing. For more information, see Using the CancellationHandlerActivity Activity.
CodeActivity	Enables you to add Visual Basic or C# code to your workflow. For more information, see Using the CodeActivity Activity.
CompensatableSequenceActivity	Compensatable version of SequenceActivity. For more information, see Using the CompensatableSequenceActivity Activity.
CompensatableTransactionScopeActivity	Compensatable version of TransactionScopeActivity. For more information, see Using the CompensatableTransactionScopeActivity Activity.
CompensateActivity	Enables you to call code to undo or to compensate for operations already performed by the workflow when an error occurs. For more information, see Using the CompensateActivity Activity.
CompensationHandlerActivity	Wrapper for one or more activities that perform compensation for a completed TransactionScopeActivity activity. For more information, see Using the CompensationHandlerActivity Activity.
ConditionedActivityGroup	Executes child activities based on a condition that applies to the ConditionedActivityGroup activity itself and based on conditions that apply separately to each child. For more information, see Using the ConditionedActivityGroup Activity.
DelayActivity	Enables you to build delays in your workflow based on a time-out interval. For more information, see Using the DelayActivity Activity.
EventDrivenActivity	Wraps one or more activities that are executed when a specified event occurs. For more information, see Using the EventDrivenActivity Activity.
EventHandlersActivity	Provides a framework for associating events with an activity. For more information, see Using the EventHandlersActivity Activity.
EventHandlingScopeActivity	Executes its main child activity concurrently with an EventHandlersActivity activity. For more information, see Using the EventHandlingScopeActivity Activity.
FaultHandlerActivity	Used to handle an exception of a type that you specify. For more information, see Using the FaultHandlerActivity Activity.
FaultHandlersActivity	Represents a composite activity that has an ordered list of child activities of type FaultHandlerActivity. For more information, see Using the FaultHandlersActivity Activity.
HandleExternalEventActivity	Used together with the CallExternalMethodActivity activity for input and output communications with a local service. For more information, see Using the HandleExternalEventActivity Activity.
IfElseActivity	Tests a condition on each branch and performs activities on the first branch for which the condition equals true. For more information, see Using the IfElseActivity Activity.
IfElseBranchActivity	Represents a branch of an IfElseActivity activity. For more information, see Using the IfElseBranchActivity Activity.
InvokeWebServiceActivity	Enables your workflow to invoke a Web service. For more information, see Using the InvokeWebServiceActivity Activity.
InvokeWorkflowActivity	Enables your workflow to invoke another workflow. For more information, see Using the InvokeWorkflowActivity Activity.
ListenActivity	A composite activity that contains only EventDrivenActivity child activities. For more information, see Using the ListenActivity Activity.
ParallelActivity	Lets you schedule two or more child SequenceActivity activity branches for processing at the same time. For more information, see Using the ParallelActivity Activity.
PolicyActivity	Used to represent a collection of rules. A rule consists of conditions and resulting actions. For more information, see Using the PolicyActivity Activity.
ReceiveActivity	Implements a service contract operation using Windows Communication Foundation (WCF).
ReplicatorActivity	Creates multiple instances of a single child activity. For more information, see Using the ReplicatorActivity Activity.
SendActivity	Invokes a client-side synchronous operation of a service using Windows Communication Foundation (WCF) .
SequenceActivity	Provides a simple way to link multiple activities together for sequential execution. For more information, see Using the SequenceActivity Activity.
SetStateActivity	Specifies a transition to a new state. For more information, see Using the SetStateActivity Activity.
StateActivity	Represents a state in a state machine workflow. For more information, see Using the StateActivity Activity.
StateFinalizationActivity	Used in a StateActivity activity as a container for child activities executed when leaving the StateActivity activity. For more information, see Using the StateFinalizationActivity Activity.
StateInitializationActivity	Used in a StateActivity activity as a container for child activities executed when entering the StateActivity activity. For more information, see Using the StateInitializationActivity Activity.
SuspendActivity	Suspends the operation of your workflow to enable intervention in the event of some error condition that requires special attention. For more information, see Using the SuspendActivity Activity.
SynchronizationScopeActivity	Executes contained activities sequentially in a synchronized domain. For more information, see Using the SynchronizationScopeActivity Activity.
TerminateActivity	Enables you to immediately end the operation of your workflow in the event of an error condition. For more information, see Using the TerminateActivity Activity.
ThrowActivity	Enables you to capture business exceptions thrown as part of the process metadata for a workflow. For more information, see Using the ThrowActivity Activity.
TransactionScopeActivity	Provides a framework for transactions and exception handling. For more information, see Using the TransactionScopeActivity Activity.
WebServiceFaultActivity	Lets you model the occurrence of a Web service fault. For more information, see Using the WebServiceFaultActivity Activity.
WebServiceInputActivity	Receives data from a Web service. For more information, see Using the WebServiceInputActivity Activity.
WebServiceOutputActivity	Responds to a Web service request made to a workflow. For more information, see Using the WebServiceOutputActivity Activity.
WhileActivity	Enables your workflow to loop until a condition is met. For more information, see Using the WhileActivity Activity.