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Parallel Activity Designer

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The Parallel activity executes a collection of child activities concurrently.

The Parallel Activity

The Parallel activity stores its child activities in a Branches collection. Use the Parallel activity instead of the Sequence activity if some of the child activities may go idle.

The Parallel activity has a CompletionCondition property that contains a user specified Visual Basic expression. The Parallel activity evaluates this property after each branch completes. If it evaluates to True, then the Parallel activity completes without executing the other branches. If the CompletionCondition does not evaluate to True, then the Parallel activity completes when all of its child activities have completed.

Using the Parallel Activity Designer

Access the Parallel activity designer in the Control Flow category of the Toolbox.

The Parallel activity designer can be dragged from the Toolbox and dropped on to the Workflow Designer surface wherever activity designers are normally placed, for example, inside of a Sequence activity designer. After dropping it into the Workflow Designer, it creates a Parallel activity, which by default contains a DisplayName of Parallel

To add an activity to the Branches collection of the parallel activity, drag some other activity designer from the Toolbox and drop it on the triangle inside the Parallel activity designer. The triangles flank the activities contained in the branches. Additional activities can be added by repeating this procedure. The activities can be reordered by dragging and dropping them within the Parallel activity designer.

Parallel Activity Properties in the Workflow Designer

The following table shows the Parallel activity properties and describes how they are used in the designer.

Property Name Required Usage
DisplayName False Specifies the friendly display name of the activity designer in the header. The default value is Parallel. The value can be optionally edited in the Properties grid or directly on the activity designer header.
Branches True Contains the collection of child activities to be executed.
CompletionCondition False Evaluated after a branch completes. If it evaluates to True, then the scheduled pending branches are canceled. If this property is not set or evaluates to False, the activity completes when all of its child activities have completed. The default value is null.

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