is a lightweight, per-instance runtime for executing a workflow program. It can be constructed to create a new workflow instance or from existing instance state. The APIs that WorkflowInstance::WorkflowInstanceControl exposes are the minimal set of runtime controls from which higher level operations can be implemented. This API set represents the entire breadth of functionality of the runtime. is an abstract class and relies on a host’s implementation of its abstract methods in order to provide host functionality such as synchronization, persistence, tracking, and extensions.
Assembly: System.Activities (in System.Activities.dll)
Thetype exposes the following members.
|Controller||Gets the WorkflowInstance::WorkflowInstanceControl instance for this .|
|HostEnvironment||Gets or sets the root environment for the workflow instance’s arguments and variables.|
|Id||Gets the unique identifier for the workflow instance.|
|IsReadOnly||Gets a value that indicates whether the workflow instance has been initialized.|
|SupportsInstanceKeys||Gets a value that indicates whether the host supports the association of with a run-time instance.|
|SynchronizationContext||Gets or sets the SynchronizationContext used for scheduling the workflow instance.|
|WorkflowDefinition||Gets the workflow definition of the workflow instance.|
|DisposeExtensions||Calls on all extensions that implement IDisposable.|
|Equals(Object)||Determines whether the specified Object is equal to the current Object. (Inherited from Object.)|
|Finalize||Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)|
|GetExtension<T>||Returns an extension of the specified type.|
|GetExtensions<T>||Returns all extensions found for the specified type.|
|GetHashCode||Serves as a hash function for a particular type. (Inherited from Object.)|
|GetType||Gets the Type of the current instance. (Inherited from Object.)|
|Initialize(Object)||Called by the host to initialize the workflow instance with the workflow run-time state.|
|Initialize(IDictionary<String, Object>, IList<Handle>)||Called by the host to initialize the workflow instance with the argument values and execution properties.|
|MemberwiseClone||Creates a shallow copy of the current Object. (Inherited from Object.)|
|OnBeginAssociateKeys||Called by the workflow runtime to notify the host that new instance keys should be associated with this instance.|
|OnBeginFlushTrackingRecords||Asynchronous call to ask host to flush pending tracking records to tracking participants.|
|OnBeginPersist||Asynchronous call to ask the host to persist the workflow.|
|OnBeginResumeBookmark||Called by the workflow runtime to notify the host that a resume bookmark operation is beginning.|
|OnDisassociateKeys||Called by the workflow runtime to notify the host that a certain set of instance keys should no longer be associated with this instance.|
|OnEndAssociateKeys||Called by the workflow runtime to notify the host that an associate keys operation is complete.|
|OnEndFlushTrackingRecords||Called by the workflow runtime to notify the host when the flush tracking records operation is complete.|
|OnEndPersist||Called by the workflow runtime to notify the host that a persist operation is complete.|
|OnEndResumeBookmark||Called by the workflow runtime to notify the host that a resume bookmark operation is complete.|
|OnNotifyPaused||Called by the workflow runtime to notify the host that the workflow instance has transitioned from the running state to the paused state.|
|OnNotifyUnhandledException||Called by the workflow runtime to notify the host an unhandled exception has occurred in the workflow instance.|
|OnRequestAbort||Called by the workflow runtime to notify the host that an abort operation has been requested for the workflow instance.|
|RegisterExtensionManager||Called by the host to register the specified extension manager, validate that all required extensions are present, and to initialize the collection of extensions to be used.|
|ThrowIfReadOnly||Throws an InvalidOperationException if the workflow instance has been initialized, as determined by IsReadOnly.|
|ToString||Returns a string that represents the current object. (Inherited from Object.)|
is single threaded and assumes that the host synchronizes all access to it. An attempt to call multiple APIs simultaneously will result in an InvalidOperationException being thrown.
Internally, a has two states: Running and Paused. The only way to cause the runtime to transition from paused to running is to call Run(). All actions (except Pause) can only be taken while the runtime is Paused. The runtime will become spontaneously Paused in the following situations:
An exception in the workflow was uncaught and escaped the root. The host will be notified through the OnNotifyUnhandledException(Exception, Activity, String) method.
The scheduler has run out of work items and is now Idle. The host will be notified through the OnNotifyPaused() method. Note that the scheduler could have run out of work items because the instance is idle or because the instance is complete. The State value of the Controller property can be used to differentiate between the two.
The host can request a change from Running to Paused by calling the RequestPause() or PauseWhenPersistable() methods of the WorkflowInstance::WorkflowInstanceControl instance returned by the Controller property. This request should not be considered to have a specific response meaning that the host should not attempt to correlate an OnNotify* or OnRequestAbort(Exception) with a specific call to pause. In response to a pause request, the runtime may transition to Paused and call OnNotifyPaused() while the scheduler still has pending work items. The State value of the Controller property can be used to determine whether the scheduler has no more work or was interrupted by a request to pause.
The RequestPause() method of the WorkflowInstance::WorkflowInstanceControl instance returned by the Controller property is the only method which can be called while the is in the Running state. All other methods will throw an InvalidOperationException if called.Given the rules for how transitions from one state to another, the public notion of Running and Paused can be defined as follows:
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.