Step 5: Defining the Workflow Event Handler

In this step, you will define a workflow event handler for the ARInvoiceEntry.OnCloseDocument workflow event. Do the following:

In the RSSVWorkOrderEntry graph, define a workflow event handler, as the following code shows.
```
        #region Workflow Event Handlers 
        public PXWorkflowEventHandler<RSSVWorkOrder, ARInvoice> OnCloseDocument 
            = null!;
        #endregion
```
In the first type parameter of the handler, you have specified the primary DAC of the form where the handler is used. As the second type parameter, you have specified the primary DAC of the form where the event is fired.
Tip:
Add the using directive for the PX.Data.WorkflowAPI namespace if it has not been added earlier.
In the RSSVWorkOrderEntry_Workflow class, bind the OnCloseDocument workflow event handler to the CloseDocument workflow event in the screen configuration: After the AddDefaultFlow method, call the WithHandlers method. In the method, add the OnCloseDocument event handler, as the following code shows.
```
                .WithHandlers(handlers =>
                {
                    handlers.Add(handler => handler
                        .WithTargetOf<ARInvoice>()
                        .OfEntityEvent<ARInvoice.Events>(
                            workflowEvent => workflowEvent.CloseDocument)
                            .Is(graph => graph.OnCloseDocument)
                            .UsesPrimaryEntityGetter<
                                SelectFrom<RSSVWorkOrder>.
                                Where<RSSVWorkOrder.invoiceNbr
                                .IsEqual<ARRegister.refNbr.FromCurrent>>>());
                })
```
In the code above, you have added a handler for a workflow event that changes the state of the invoice workflow. In the UsesPrimaryEntityGetter method, you have selected the repair work order whose state should be updated by the number of the invoice that has been closed.
Tip:
Make sure that you have added the using directives, which are shown in the following code.
```
using PX.Objects.AR;
using PX.Data.WorkflowAPI;
```
In the GetCompletedBehavior private static method, add the event handler by using the WithEventHandlers method, as the following code shows.
```
            .WithEventHandlers(handlers =>
            {
                handlers.Add(graph => graph.OnCloseDocument);
            });
```

In the lambda expression for the WithTransitions method, add the transition from the Completed workflow state to the Paid workflow state, as the following code shows.

                        transitions.AddGroupFrom<States.completed>(
                            transitionGroup =>
                        {
                            transitionGroup.Add(transition => 
                                transition.To<States.paid>()
                                .IsTriggeredOn(graph => graph.OnCloseDocument));
                        });

Save your changes.