Business Rules/Logic

Custom modal forms can be used to collect parameters from the user and pass them to business rules for processing.

A custom data controller without a command can define fields, presentation views, and actions. Such controllers may be used as confirmations for actions for the purpose of collecting input parameters.

Let’s consider the steps involved in the creation of a confirmation data controller using a Northwind sample application.

Child views in a master/detail relationship will automatically hide the foreign key field to prevent duplicate display of the field value. This means that the Supplier Company Name field in the list of supplier products controller is hidden.

However, sometimes the user may want to change the foreign key of a child record. This may occur if a product is incorrectly associated with a supplier. One solution is to navigate to the standalone Products page where the supplier lookup is visible. A better alternative would be to create a custom action displaying a modal form that will allow the user to change the foreign key field in the child list of products.

Start the Project Designer. In the Project Explorer, switch to the Controllers tab. On the toolbar, press New Controller icon.

Give this controller the following name:

Press OK to save the controller. In the Project Explorer, right-click on SupplierSelector / Fields node, and select New Field option.

Give this field the following properties:

Press OK to save. Create another field:

Save this field, and create one more.

Save the field. Right-click on SupplierSelector / Business Rules node, and select New Business Rule option.

Give this business rule the following properties:

set @ProductName = @Context_ProductName
set @SupplierCompanyName = @Context_SupplierCompanyName

Press OK to save.

In the Project Explorer, right-click on Products / Actions / ag1 (Grid) node and select New Action option.

Give this action the following properties:

Press OK to save. Right-click on Products / Business Rules node, and select New Business Rule option.

Use the following properties:

--update the product supplier
update Products
set SupplierID = @Parameters_SupplierID
where ProductID = @ProductID
--'forget' the previously selected product
set @ProductID = null
--force the data view to refresh
set @Result_Refresh = 1

Press OK to save.

On the toolbar, press Browse.

Navigate to the Suppliers page, and select a supplier. In the context menu of a product, select Change Supplier.

A custom modal form will open, displaying the current Product and Supplier.

Use the lookup to select a new supplier.

Press OK to confirm, and the supplier of the product will change to the new supplier.

The Code Formula field is an expression in the language of your project (C# or Visual Basic) that calculates the value of the field every time the row values are changed in response to Calculate action.

Let’s add an Extended Price field in Order Details that will calculate the extended price of the order item using Unit Price, Quantity, and Discount.

Start the Project Designer. In the Project Explorer, switch to the Controllers tab, right-click on OrderDetails / Fields node, and select New Field option.

Give this field the following settings:

Convert.ToDecimal(unitPrice) * 
    Convert.ToDecimal(quantity) * 
    (1 - Convert.ToDecimal(discount))

Press OK to save the field.

At the top of the Project Browser window, switch to the Data Fields tab. Create a new data field with the following configuration:

Press OK to save.

On the toolbar, press Browse button. Navigate to the Order Details page, and create a new record. Specify a Unit Price, Quantity, and Discount, and the Extended Price will be calculated when you press Tab or click outside of the changed field.

If you change any of the field values and shift focus to another field, the Extended Price will refresh.

The code generator automatically creates a business rule file using the Code Formula expression. The resulting file can be seen below.

C#:

using System;
using MyCompany.Data;

namespace MyCompany.Rules
{
    public partial class OrderDetailsBusinessRules : MyCompany.Data.BusinessRules
    {

        [ControllerAction("OrderDetails", "Calculate", "ExtendedPrice")]
        public void CalculateOrderDetails(int? orderID,
            string orderCustomerID, string orderCustomerCompanyName,
            string orderEmployeeLastName, string orderShipViaCompanyName,
            int? productID, string productProductName,
            string productCategoryCategoryName,
            string productSupplierCompanyName, decimal? unitPrice,
            short? quantity, float? discount)
        {
            UpdateFieldValue("ExtendedPrice", 
                Convert.ToDecimal(unitPrice) *
                Convert.ToDecimal(quantity) *
                (1 - Convert.ToDecimal(discount)));
        }
    }
}

Visual Basic:

Imports MyCompany.Data
Imports System

Namespace MyCompany.Rules
    
    Partial Public Class OrderDetailsBusinessRules
        Inherits MyCompany.Data.BusinessRules
        
        <ControllerAction("OrderDetails", "Calculate", "ExtendedPrice")> _
        Public Sub CalculateOrderDetails(ByVal orderID As Nullable(Of Integer),
                                         ByVal orderCustomerID As String,
                                         ByVal orderCustomerCompanyName As String,
                                         ByVal orderEmployeeLastName As String,
                                         ByVal orderShipViaCompanyName As String,
                                         ByVal productID As Nullable(Of Integer),
                                         ByVal productProductName As String,
                                         ByVal productCategoryCategoryName As String,
                                         ByVal productSupplierCompanyName As String,
                                         ByVal unitPrice As Nullable(Of Decimal),
                                         ByVal quantity As Nullable(Of Short),
                                         ByVal discount As Nullable(Of Single))
            UpdateFieldValue("ExtendedPrice",
                Convert.ToDecimal(unitPrice) *
                Convert.ToDecimal(quantity) *
                (1 - Convert.ToDecimal(discount)))
        End Sub
    End Class
End Namespace