Confirmation

This topic applies to Windows Workflow Foundation 4 (WF4).

This sample shows four common scenarios surrounding the use of CompensableActivity and confirmation. The sample runs four workflows to show confirmation. This sample is available in declarative and imperative versions.

Confirm a Compensable Activity

The first workflow demonstrates how to confirm a compensable activity and consists of a sequence of two CompensableActivity instances. After the completion of the second CompensableActivity a confirm activity confirms the first activity. When the workflow successfully completes, all CompensableActivity instances that have not been confirmed or compensated are automatically confirmed using the default order. Without the confirm, the second CompensableActivity would have been confirmed first.

Explicit Compensation

The second scenario shows the affect on default confirmation when a CompensableActivity is explicitly compensated. The workflow consists of a sequence of two CompensableActivity activities, after the second completes the first is explicitly compensated. As a result when the workflow, completes only the second CompensableActivity is confirmed.

Controlling the Order of Confirmation for Nested CompensableActivity Activities

The third scenario shows how to control the order of confirmation for nested CompensableActivity. The scenario consists of a CompensableActivity as the root of the workflow. The body of the root CompensableActivity is a sequence of three CompensableActivity. The ConfirmationHandler for the root CompensableActivity is a sequence that specifies to confirm the first then the second nested CompensableActivity. When the workflow completes it confirms the root CompensableActivity, which then confirms the first, second and third nested CompensableActivity, in that order. As a result, the default confirmation order is essentially reversed. Because the third CompensableActivity was not explicitly confirmed as part of the root CompensableActivity by the ConfirmationHandler, it is confirmed according to the default order. However, because it is the only unconfirmed CompensableActivity this just means it is confirmed.

Scoping of Variables

The fourth scenario shows how the lifetime of variables defined for a CompensableActivity or one of their parents are still in scope when the CompensationHandler, ConfirmationHandler or CancellationHandler handlers are executed even if the activity has completed or the workflow has completed. The workflow consists of a sequence of two CompensableActivity. In the body of the first, the variable mySum is set to the sum of 5 and 10 and the result printed. In the body of the second CompensableActivity, the sum is set to the sum of the existing sum and 7 and the result printed. A custom confirmation handler is defined for the first CompensableActivity, which prints the sum, subtracts 7 and prints the sum again. It is clear by inspecting the printed sums that the variable is in scope not only for the bodies of both CompensableActivity but the ConfirmationHandler as well.

To run the sample

1. Load the solution in Visual Studio 2010.

2. Run the ConfirmationSample.exe application.

3. Observe the following output:

    Explicit confirmation:
    Start of workflow
    CompensableActivity1: Body
    CompensableActivity2: Body
    CompensableActivity1: Confirmation Handler
    End of workflow
    CompensableActivity2: Confirmation Handler

    Explicit compensation:
    Start of workflow
    CompensableActivity1: Body
    CompensableActivity2: Body
    CompensableActivity1: Compensation Handler
    End of workflow
    CompensableActivity2: Confirmation Handler

    Custom confirmation handler:
    Start of workflow
    CompensableActivity1: Body
    CompensableActivity2: Body
    CompensableActivity3: Body
    End of workflow
    CompensableActivity1: Confirmation Handler
    CompensableActivity2: Confirmation Handler
    CompensableActivity3: Confirmation Handler

    Variable access in a confirmation handler:
    Start of workflow
    CompensableActivity1: Body
    CompensableActivity1: The sum is: 15
    CompensableActivity2: Body
    CompensableActivity2: Adding 7 to the sum
    CompensableActivity2: The sum is now: 22
    End of workflow
    CompensableActivity2: Confirmation Handler
    CompensableActivity1: Confirmation Handler
    CompensableActivity2: The sum is: 22
    CompensableActivity2: After subtracting 12 the sum is now: 10

    Press ENTER to exit.</pre>

Note:

The samples may already be installed on your computer. Check for the following (default) directory before continuing. <InstallDrive>:\WF_WCF_Samples If this directory does not exist, go to Windows Communication Foundation (WCF) and Windows Workflow Foundation (WF) Samples for .NET Framework 4 to download all Windows Communication Foundation (WCF) and WF samples. This sample is located in the following directory. <InstallDrive>:\WF_WCF_Samples\WF\Basic\Compensation\Confirmation