BlockingOutput Activity

Activity Description:

The BlockingOutput activity facilitates synchronous execution of workflow activities with an active form.

This is typically used in forms, whose fields need to be updated based on the output of multiple workflow activities of the same workflow, executed one after the other, without closing the form.

Activity Properties:

The properties under each group are described in this topic.

Name & Description

The properties in the Name & Description group have been described below. You can use these properties to specify the name and description for the activity.

Name - This property can be used to specify a name for the activity.

Property Type: Optional (This property needs to be set only if necessary.)

Description - This property specifies a brief description to be displayed for the activity.

Property Type: Optional (This property needs to be set only if necessary.)

Configuration

Specify the Output to be returned to the application that calls this workflow when this activity is encountered.

Example for a Block Output Activity:

Step 1: Create a Microsoft SharePoint Workflow.

Step 2: In Microsoft SharePoint Workflow, Start activity is connected to a Block activity.

Step 3: Click on the property 'Set Blocking Output' following window pops up. Set it as "TRUE" as shown in the figure.

Step 4: Associate the workflow to a list in the Microsoft SharePoint website on the event 'Item Adding'.

Output: Whenever an attempt is made to add an item to the list, the Blocking Output activity would prevent it and display the following error message:

Item adding is stopped by the workflow.

Note:
- This activity works only when the event is in process like Item Adding, Item Updating and not for the events like Item Added, Item Updated because once the process is completed the item cannot be blocked any more. This activity is useful when you want to prevent the users from performing specific tasks. For example: If you want to prevent users from updating an existing item.
- When you use the BlockingOutput activity for returning the blocking output value, ensure that all the activities being executed before this activity, do not have sleeping behavior. For example: There should not be any activities, such as human or scheduler activities, which go to the sleep mode. However, Workflow activity with some specific settings can be included before this activity. For more information about the Workflow activity, see Workflow Activity.