CacheAttached: To Replace Field Attributes in CacheAttached

The following activity will walk you through the process of replacing field attributes in CacheAttached event handlers.

Story

The RSSVWorkOrder DAC holds the data of the Repair Work Orders (RS301000) data entry form. The data of this DAC is also displayed on the Assign Work Orders (RS501000) processing form. (You have developed both of these forms for the Smart Fix company.) You need to add the following fields to this DAC:

DefaultAssignee: The employee that has the fewest assigned repair work orders
AssignTo: The employee the repair work order will be assigned to

On the Assign Work Orders form, you need to calculate the values of these fields by using attributes. You do not need these calculations for the data entry form.

Process Overview

In this activity, you will add attributes that calculate the values of the DefaultAssignee and AssignedTo fields of the RSSVWorkOrder DAC. Because you need these calculations only for the Assign Work Orders (RS501000) form, you will add these attributes by using the CacheAttached event handler.

System Preparation

Before you begin replacing field attributes in CacheAttached event handlers, do the following:

Prepare an MYOB Acumatica instance by performing the Test Instance for Customization: To Deploy an Instance with a Custom Form that Implements a Workflow prerequisite activity.
Create a processing form without filtering parameters by performing the Processing Forms: To Create a Simple Processing Form prerequisite activity.

Step 1: Extending the DAC with New Fields

Add the new fields to the RSSVWorkOrder DAC as follows:

In the RSSVWorkOrder class, define the DefaultAssignee field, as shown in the following code.

        #region DefaultAssignee
        [PXInt]
        [PXUIField(DisplayName = "Default Assignee")]
        public virtual int? DefaultAssignee { get; set; }
        public abstract class defaultAssignee :
            PX.Data.BQL.BqlInt.Field<defaultAssignee>
        { }
        #endregion

Define the AssignTo field, as shown below.

        #region AssignTo
        [PXInt]
        [PXUIField(DisplayName = "Assign To")]
        public virtual int? AssignTo { get; set; }
        public abstract class assignTo : PX.Data.BQL.BqlInt.Field<assignTo> { }
        #endregion

Build the project.

Step 2: Replacing the Attributes

In this step, you will add the attributes to the RSSVWorkOrder DAC fields by using the CacheAttached event handlers of these fields in the RSSVAssignProcess graph. These attributes will be used for the RSSVWorkOrder DAC fields only on the Assign Work Orders (RS501000) form. Instead of completely replacing attributes, you will add the needed attributes to the fields by including the PXMergeAttributes attribute in the list of assigned attributes.

To implement the calculation of field values for the RSSVAssignProcess graph, do the following:

In the RSSVAssignProcess.cs file, add the PX.TM using directives.
To add the PXDBScalar attribute to the DefaultAssignee field, add the following event handler to the RSSVAssignProcess graph.
```
        [PXMergeAttributes(Method = MergeMethod.Append)]
        [Owner(IsDBField = false, DisplayName = "Default Assignee")]
        [PXDBScalar(typeof(SelectFrom<OwnerAttribute.Owner>.
            LeftJoin<RSSVEmployeeWorkOrderQty>.
            On<OwnerAttribute.Owner.contactID.IsEqual<
                RSSVEmployeeWorkOrderQty.userID>>.
            Where<OwnerAttribute.Owner.acctCD.IsNotNull>.
            OrderBy<RSSVEmployeeWorkOrderQty.nbrOfAssignedOrders.Asc,
                RSSVEmployeeWorkOrderQty.lastModifiedDateTime.Asc>.
            SearchFor<OwnerAttribute.Owner.contactID>))]
                protected virtual void _(
            Events.CacheAttached<RSSVWorkOrder.defaultAssignee> e)
        { }
```
For the system to calculate the value of the DefaultAssignee field, you have used the PXDBScalar attribute. The PXDBScalar attribute selects the first record that matches the query specified in the attribute. In the query, you have selected records in ascending order by the number of assigned work orders.
To display the employee name instead of its ID (which is an integer) and display the selector for the column if it is editable, you have assigned the Owner attribute to the DefaultAssignee field. Since the DefaultAssignee field does not exist in the database, in the Owner attribute, you have specified IsDBField = false.
To add the PXUnboundDefault attribute to the AssignedTo field, add the following event handler to the RSSVAssignProcess graph.
```
        [PXMergeAttributes(Method = MergeMethod.Append)]
        [Owner(IsDBField = false, DisplayName = "Assign To")]
        [PXUnboundDefault(typeof(RSSVWorkOrder.assignee.When<
            RSSVWorkOrder.assignee.IsNotNull>.
            Else<RSSVWorkOrder.defaultAssignee>))]
        protected virtual void _(
            Events.CacheAttached<RSSVWorkOrder.assignTo> e)
        { }
```
The system sets the value of the AssignedTo field to the employee selected for the work order on the Repair Work Orders (RS301000) form (if the value is not null) or to the default assignee specified in the DefaultAssignee field (if the value selected on the Repair Work Orders form is null). You have defined this behavior by using the PXUnboundDefault attribute.
Build the project.