Windows Workflow Foundation is a framework, not a language. It is cable to correctly handle persistence and compensation.
This slide was taken directly from the PDC slide decks from Microsoft. The key take-aways I want you to leave with today are the following: Workflows are a set of activities. Workflows run within a Host Process, which can be any application or server that you code. You can use the base activities and bases classes within the workflow framework to build your own activities that are specific to your business or domain. The components of the Windows Workflow Foundation are : The Base Activity Library - These are the out-of-the box activities and base classes to use when building your workflows and custom activities. The Runtime Engine – This is the workflow execution engine and state manager for workflows. The runtime is what is hosted within the Host Process and it controls all the workflows instantiated within that host process. The Runtime Services – The runtime is extensible by using runtime services. The services can be registered with the runtime to provide hosting flexibility and communication. For example, out of the box you can find the persistence service and tracking service which allows you to persist your workflow state to a SQL data store and track you workflow process. You can create your own services to provide more communication options between the host process and the workflows, or you can even replace a provided service if you want. For example, you could provide your own persistence service that persists the workflows to a file based store rather than a SQL Server based store. Finally, the Visual Designer – This is the developer experience for WF. This designer is integrated with Visual Studio 2005 and allows for developers to easily map out and navigate workflows. The designer can also be hosted within your own application so that you can expose it to end users so that they can modify workflows on the fly.
Activities are added to a workflow programmatically in a manner similar to adding XML DOM child nodes to a root node.
A key advantage of defining your logic with rules and declarative conditions is that they can be modified at run time by doing dynamic updates using workflow changes. In addition, rules let you separate your business logic from a workflow in order to share those rules with other workflows. Finally, defining business logic in rules allows for advanced tools, such as dependency visualization and impact analysis tools, to be built on top of the object model.
Host process can be a console, Win Forms, ASP.NET or Web service etc.,
Workflow markup is based on XAML . It enables the developers and designers to model business logic declaratively. With this declarative model, it can also possible to activate workflow by directly loading a workflow markup file into the workflow runtime engine at runtime.
If you use custom activities in your workflow markup code, the assembly containing your custom activity must be referenced through a type provider in your code. TypeProvider typeProvider = new TypeProvider(null); typeProvider. AddAssembly (typeof(CustomActivity).Assembly); workflowRuntime.AddService(typeProvider); In addition to code you can reference these custom assemblies from markup also: < SequentialWorkflowActivity x:Class =&quot;XAMLWorkflow.Workflow1&quot; x:Name =&quot;Workflow1&quot; xmlns:ns0 =&quot;clr-namespace:BusinessActivities; Assembly =CustomActivityAssembly, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null&quot; &quot;> <ns0: CustomActivity x:Name=&quot;CustomActivity1&quot;/> </SequentialWorkflowActivity> To start workflow: WorkflowInstance instance = workflowRuntime.CreateWorkflow(workflowDefinitionReader); instance.Start();
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. Once the activity Execute method returned the Closed value of ActivityExecutionStatus. Then runtime claims this activity for disposing. If you return Closed value of this enumerator then that activity will be claimed for disposing. If returns Executing indicates to runtime that activity have extra work to do.
In Sequential activity the order of its actions is specified its design time. In Event-driven activity the order of its actions is determined at runtime in response to external events.
To call a method in the host application from the workflow you can use the CallExternalMethodActivity activity. Used with the HandleExternalEventActivity activity for input and output communications with a local service CancellationHandlerActivity: Used to contain cleanup logic for a composite activity that is canceled before all the composite activity's child activities are finished executing. CodeActivity : Enables you to add Visual Basic or C# code to your workflow. CompensatableSequenceActivity : Compensatable version of SequenceActivity. CompensatableTransactionScopeActivity : Compensatable version of TransactionScopeActivity. CompensateActivity: Enables you to call code to undo or to compensate for operations already performed by the workflow when an error occurs . CompensationHandlerActivity: Wrapper for one or more activities that perform compensation for a completed TransactionScopeActivity 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. DelayActivity : Enables you to build delays in your workflow based on a time-out interval. Its job is to wait for a predefined time before continuing the execution of workflow.
EventDrivenActivity : Wraps one or more activities that are executed when a specified event occurs. EventHandlersActivity: Provides a framework for associating events with an activity. EventHandlingScopeActivity : Executes its main child activity concurrently with an EventHandlersActivity activity. FaultHandlerActivity: Used to handle an exception of a type that you specify FaultHandlersActivity : Represents a composite activity that has an ordered list of child activities of type FaultHandlerActivity. HandleExternalEventActivity: Used together with the CallExternalMethodActivity activity for input and output communications with a local service. IfElseActivity : Tests a condition on each branch and performs activities on the first branch for which the condition equals true . It is similar to if-else statements in C#. IfElseBranchActivity : Represents a branch of an IfElseActivity activity InvokeWebServiceActivity: Enables your workflow to invoke a Web service. InvokeWorkflowActivity : Enables your workflow to invoke another workflow. ListenActivity: It is a composite activity that contains only EventDrivenActivity child activities. ParallelActivity : Lets you schedule two or more child SequenceActivity activity branches for processing at the same time. PolicyActivity : Used to represent a collection of rules. A rule consists of conditions and resulting actions ReplicatorActivity : Creates multiple instances of a single child activity.
SequenceActivity : Provides a simple way to link multiple activities together for sequential execution. SetStateActivity : Specifies transition to new state. StateActivity: Represents a state in a state machine workflow. StateFinalizationActivity : Used in a StateActivity activity as a container for child activities executed when leaving the StateActivity activity. StateInitializationActivity: Used in a StateActivity activity as a container for child activities executed when entering the StateActivity activity. SuspendActivity : Suspends the operation of your workflow to enable intervention in the event of some error condition that requires special attention. SynchronizationScopeActivity : Executes contained activities sequentially in a synchronized domain. TerminateActivity : Enables you to immediately end the operation of your workflow in the event of an error condition. ThrowActivity : Enables you to capture business exceptions thrown as part of the process metadata for a workflow. TransactionScopeActivity: Provides a framework for transactions and exception handling WebServiceFaultActivity: Lets you model the occurrence of a Web service fault. WebServiceInputActivity: Receives data from a Web service WebServiceOutputActivity: Responds to a Web service request made to a workflow WhileActivity: Enables your workflow to loop until a condition is met,
AEC stands for ActivityExecutionContext . AES stadns for ActivityExecutionStatus. Most of the activities do nothing in the Initialized state. If you want you can make any initialization setup for your activity. The solid red line represents the workflow runtime engine is responsible for transitioning an activity from the Initialized state to the Executing state, or transitioning from the Closed state to the Compensating state. The solid yellow line represents the parent activity is responsible for transitioning a child activity from the Executing state to the Closed state. If you create a custom composite activity, you must handle this yourself. The solid blue line represents the workflow runtime engine is responsible for transitioning an activity from the Executing , Canceling , or Compensating state to the Faulting state. The dashed yellow line represents the workflow runtime engine is responsible for transitioning an activity from either the Canceling state, Compensating state, or Faulting state to the Closed state. An activity can’t move from closed state to executing state . Any attempt by calling Execute() method from closed state will cause an exception. An activity may only close when all children activities are either in their Closed or Initialized states. Because this is a recursive rule, it means that the entire tree below an activity, which is attempting to close, must be Closed or Initialized for the call to succeed.
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. The Execute, Cancel and Close state are the only execution status changes that a parent activity can control through the AEC. All other activity states are controlled by the workflow runtime engine. An activity can only close when all spawned execution contexts (CreateExecutionContext) have been completed (CompleteExecutionContext). Violation of this behavior causes an exception to be thrown by the workflow runtime engine.
Metadata is related to activities in the same way that attributes are related to .NET Framework classes. Metadata is only configurable at design time and, once an activity is built, cannot be changed System.Workflow.ComponentModel.Activity.Name is a metadata because the name of an activity in a workflow's tree is part of the definition of the workflow. Instance data, on the other hand, maps to properties and fields on classes. In certain cases, you need an activity to register a property that can be used by other activities in a workflow. This kind of property is called an attached property , Attached Property is a specialized form of dependency property. You register an attached property using the RegisterAttached() method of the DependencyProperty class.
Custom activities can also be extended to have their own look and feel within the designer and contain their own validation code of for the smart tags (Like the code shape warned us we needed to set the execute code handler). These are done with companion classes. You create a companion class and use an attribute on the activity class to link the two.
WWF is flexible and extensible. The sequential workflow style is straightforward and useful for repetitive, predictable operations that are always the same. The state machine workflow style consists of a set of event-driven states. The data-driven workflow style relies on data to determine whether or not certain activities are run based on a local data state. When you start the runtime, it can then reload any workflow instances that were executing the last time the application was executed by reading these instances from the persistence store . To support this persistence store it need to support persistence service also.
In host application, you must create an instance of this class and pass the type specification of your workflow by using the CreateWorkflow() method.
Simply like .NET or C, C++ methods parameter passing is not allowed for workflows. Let us assume your workflow have properties such as Salary . Then in dictionary of name-value pairs the name should be Salary and value should be corresponding val. If the a parameter match is found then the property setter is called and the value of the parameter is passed to this setter.
The durability means workflows can be unloaded from memory while awaiting input and serialized into a persistent store, such as a SQL database or XML file. Whenever the input is received, the workflow runtime engine loads the workflow state information back into memory and continues execution of the workflow. With a custom activity serializer, you can decide which members are serialized and how they are serialized . This determines if those members are visible or hidden in a workflow designer.
WorkflowMarkupSerializer: This is the base serialization type used in the serialization infrastructure. This type provides some of the basic services for serialization that implement the serialization rules. The serializers for activities or any other custom serializers for custom activities must inherit from this class. ActivityMarkupSerializer : Inherits from the WorkflowMarkupSerializer class. This type is used to serialize all basic activities. These are activities that are not composite activities. CompositeActivityMarkupSerializer: Inherits from the ActivityMarkupSerializer class and provides the serialization for composite activities. CompositeActivityMarkupSerializer adds more methods to process child activities, which can be serialized using their own serialization providers. If you create a custom serializer, activity authors must provide a reference to the custom serializer as illustrated in the following code example. [ DesignerSerialize r(typeof(ExampleActivityMarkupSerializer), typeof(WorkflowMarkupSerializer))] public class ExampleActivity : Activity { } The first parameter specifies the serializer that should be used to serialize the instance of the class on which the attribute has been defined. The second parameter specifies the base type of the serializer. The base type of the serializer specifies the serialization scheme to use.
Persistence service , which stores the execution details of a workflow instance in a SQL database An example of creating custom service is : creating a persistence service that uses an XML file instead of a database for storage. Windows Workflow Foundation provides the SqlWorkflowPersistenceService that integrates well with Microsoft SQL Server 2005 Express, SQL Server 2000 or later, or SQL Server 2000 Desktop Engine (MSDE) to persist workflow information easily and efficiently.
By using this performance monitor tool , you can configure performance counters to record performance data and set system alerts to notify you when a specified counter's value is above or below defined threshold. <?xml version=&quot;1.0&quot;?> <configuration> <configSections> <section name=&quot; CustomWorkflowRuntimeSettings &quot; type=“xxx&quot; /> </configSections> < CustomWorkflowRuntimeSettings Name=&quot;Workflow1&quot; EnablePerformanceCounters =&quot;false&quot;> <!-- Define common parameters and declare services required for your workflow runtime --> </CustomWorkflowRuntimeSettings> </configuration>
The configuration file can be app.config or web.config according to host application.
All Logs all messages received Off Does not log any messages Critical Logs only messages deemed as critical Error Logs critical and error messages Warning Logs critical, error and warning messages Information Logs critical, error, warning and information messages VerboseLogs Critical, error, warning, information and verbose messages
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