QueryActivatableWorkflowsCommand Class

Definition

Namespace:

System.Activities.DurableInstancing

Assembly:

System.Activities.dll

Represents the command that a generic host executes against an instance store to retrieve activation parameters. The generic host uses these activation parameters to create a workflow host, which in turn loads a runnable service instance.

public ref class QueryActivatableWorkflowsCommand sealed : System::Runtime::DurableInstancing::InstancePersistenceCommand

public sealed class QueryActivatableWorkflowsCommand : System.Runtime.DurableInstancing.InstancePersistenceCommand

type QueryActivatableWorkflowsCommand = class
    inherit InstancePersistenceCommand

Public NotInheritable Class QueryActivatableWorkflowsCommand
Inherits InstancePersistenceCommand

Inheritance

Object

InstancePersistenceCommand

QueryActivatableWorkflowsCommand

Remarks

An instance is activatable, if it is not in the suspended state or the completed state and satisfies the following conditions:

• The instance is runnable. An instance in the persistence database is considered as runnable if it satisfies the following conditions:

  • The instance is unlocked and has a pending timer that has expired.

  • The instance is unlocked and its status is Executing.

  • The instance has an expired lock on it.

• There is no workflow host capable of loading the instance is running on the local computer.

An instance store should periodically search for activatable workflow instances that belong to a workflow host that uses the store. It should raise the HasActivatableWorkflowEvent when it finds an activatable instance in the persistence store. If the instance store does not find an activatable instance in the persistence store, it should continue to monitor the persistence store for any activatable instances.

After raising the HasActivatableWorkflowEvent, the instance store should stop monitoring the persistence store for activatable instances until it receives and executes the QueryActivatableWorkflowsCommand. The monitoring continues only if the command execution does not return any activatable workflow instances.

When a generic host receives this event, it executes the QueryActivatableWorkflowsCommand against the instance store to obtain activation parameters required to create a workflow host. The generic host uses these activation parameters to create a workflow host, which in turn loads and runs the service instance. The activation parameters for the WAS activation type are: Site Name, Application Path (relative to the site), and Service Path (relative to the application). An instance store could return multiple sets of these three activation parameters.

A generic host is a host that has an XName parameter named ActivationType, which should be set to a value supported by the instance store. Currently, the SQL Workflow Instance Store supports generic hosts with ActivationType parameter set to value: WAS. If the ActivationType is not set at all, the SQL Workflow Instance Store treats the host as a generic host.

Note

The Workflow Management Service that ships with the code named "Dublin" (Application Server Extensions for .NET 4.0) is a generic host that has the activation type set to WAS.

Constructors

QueryActivatableWorkflowsCommand()

Initializes an instance of the QueryActivatableWorkflowsCommand class.

Properties

AutomaticallyAcquiringLock	Indicates whether the command could attempt to acquire a lock on the instance. (Inherited from InstancePersistenceCommand)
IsTransactionEnlistmentOptional	Returns a value that indicates whether the persistence provider may choose not to enlist in the ambient transaction (Transaction.Current) when executing this command. (Inherited from InstancePersistenceCommand)
Name	Gets the name of the persistence command. (Inherited from InstancePersistenceCommand)

Methods

Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)
Validate(InstanceView)	Validates the command. (Inherited from InstancePersistenceCommand)