Windows Workflow Foundation By Jayesh Chudasama


Workflow Activities
September 11, 2006, 9:20 pm
Filed under: Books & writing, Functional

Activity represents a process step in a workflow process or a request for execution of a business task in the context of a workflow process.

For example: Credit request process incorporates activities like Evaluate request, Approve request and Send money.

The state attribute describes the current state of execution of the activity (e.g., running, suspended, completed); an activity is activated according to the process logic of the in the underlying process model. 

There are two types of activities in Windows Workflow.  

  1. The simple activity
  2. The composite activity

What makes Windows Workflow Foundation very different from traditional workflow engines is that the engine has no fixed underlying language or grammar. Instead the engine chains a set of activities that are supplied by Microsoft and created by you the developer. Microsoft-supplied constructs include “If,” “Code” blocks, activities for web services, and many more.

In addition, you can create your own control flow activities such as “do until” but more likely you will be creating higher level activities such as the “Receive Order” activity described previously. By using an activity execution methodology rather than a language, Windows Workflow Foundation is able to support a broad range of scenarios and you can reuse your activities across multiple workflows.

The set of flow control activities that ship with Windows Workflow Foundation include the following:

Control flow activities

Sequence, Parallel, While, IfElse, Listen, EventDriven, ConditionedActivityGroup, Replicator, Delay

Transaction and exception activities

ExceptionHandler, Throw, Compensate, Suspend, and Terminate

Data/form-centric activities

Data/form-centric activities enable you to bind data from forms and easily surface that information into a workflow for example UpdateData, SelectData, WaitForData and WaitForQuery

Communication activities

InvokeWebService, WebServiceReceive, WebServiceResponse, InvokeMethod, and EventSink. The web services activities give you the capability to consume and expose web services; more advanced activities such as the conditioned activity group enable policy- or rules-based condition evaluation.

The code activity

There are three additional activities that are specific for the state machine workflow model: StateInitalization, State, and SetState.

Each activity is derived from the Activity base class and includes the code that will execute when the activity and a set of design-time properties for use in the designer is called.

Read more about Windows Workflow in Presenting Windows Workflow Foundation.
 

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