Business Rules/Logic

The core framework of your application always tries to create a class with the name YourProjectNamespace.Rules.SharedBusinessRules whenever it receives a request to process data on the server. The framework interacts with the class instance in order to determine if any custom business logic is implemented in the application. This happens when data is selected, updated, inserted, deleted, and when custom actions are requested.

The name YourProjectNamespace in the namespace entered in the project settings. The default namespace is MyCompany.

You can enable shared business rules if you select Settings of your project and choose the Business Logic Layer option. Toggle the check box in the Shared Business Rules section, click Finish button to save the changes.

If you generate the app then the class file SharedBusinessRules.cs(vb) will be created either in ~/App_Code/Rules folder on in the ~/Rules folder of the application class library. This depends on the type of your projects.

Class SharedBusinessRules provides a convenient placeholder for the business logic that may apply to all data controllers of your web application.

Enter the following code in the code file of shared business rules.

C#:

using System;
using System.Data;
using System.Collections.Generic;
using System.Linq;
using MyCompany.Data;

namespace MyCompany.Rules
{
    public partial class SharedBusinessRules : MyCompany.Data.BusinessRules
    {
        [ControllerAction("", "grid1", "Select", ActionPhase.Before)]
        protected void TellTheUserWhatJustHappened()
        {
            if (!IsTagged("UserIsInformed"))
            {
                Result.ShowMessage(
                    "You just have requested data from '{0}' controller", 
                    ControllerName);
                AddTag("UserIsInformed");
            }
        }
    }
}

Visual Basic:

Imports MyCompany.Data
Imports System
Imports System.Collections.Generic
Imports System.Data
Imports System.Linq

Namespace MyCompany.Rules

    Partial Public Class SharedBusinessRules
        Inherits MyCompany.Data.BusinessRules

        <ControllerAction("", "grid1", "Select", ActionPhase.Before)>
        Protected Sub TellTheUserWhatJustHappened()
            If (Not IsTagged("UserIsInformed")) Then
                Result.ShowMessage(
                    "You just have requested data from '{0}' controller",
                    ControllerName)
                AddTag("UserIsInformed")
            End If
        End Sub

    End Class
End Namespace

Save the file and navigate to any page of your web application that contains data. Here is what you will see at the top of the page if you view the Suppliers in the Northwind sample.

If you continue sorting, filter, and paging the suppliers then the message will continue to be displayed at the top. If you start editing or select a supplier then the message from the child view will popup.

We are using IsTagged and AddTag methods to display the messages once in the lifecycle of the page instance in the browser window. If the data view on the page is not tagged then the message is displayed and the tag UserIsInformed is assigned to it.

The message will eventually disappear as soon as user invokes available data view actions.

Method TellTheUserWhatJustHappened is called every time the data is selected. This happens when the data is sorted, paged, changed, or if a filter is applied. Data view tagging ensures that the message will be sent to the client one time only.

If you navigate away from the page and come back using the Back button of your web browser then the tag is restored and no message will be displayed. If you click ahead and arrive to a non-historical version of the page then the data view tags will be blank and the message will show up once when the first attempt to select data is executed on the server.

The business logic implemented in this shared business rules example will be engaged for all data pages of your web application whenever the grid1 view of any controller requires data. This applies to an application with a single data page and will also be true in the application with three hundred data pages.

If you have existing controller-specific business rules, then make sure that their base class is changed from BusinessRules to SharedBusinessRules. If you create new controller-specific business rules, then the code generator will automatically specify the SharedBusinessRules class as their base.

The Subtotal field is now present in the application. The field does not reflect changes when new order items are entered. We will add a business rule to the Orders controller and add a code expression for Subtotal. This code expression will use the rule to calculate the subtotal.

In the Project Explorer, switch to Controllers tab. Double-click on the Orders controller. In the Handler field, type:

OrdersBusinessRules

Press OK to save the controller, exit the Designer, and Generate the project. The business rule placeholder file will be created.

When generation is complete, click on the project name in the web application generator and press Develop. Microsoft Visual Studio or Visual Web Developer will open. In the Solution Explorer on the right side of the screen, double-click on App_Code /Rules / OrdersBusinessRules.cs(vb).

Paste in the following code:

C#:

using MyCompany.Data;
using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
namespace MyCompany.Rules
{
    public partial class OrdersBusinessRules : MyCompany.Data.BusinessRules
    {
        public decimal CalculateOrderDetailsTotal(int? orderID)
        {
            using (SqlText calc = new SqlText(@"select sum(unitprice * 
                    quantity * (1 - discount)) from 
                    [Order Details] where OrderID= @OrderID"))
            {
                calc.AddParameter("@OrderID", orderID);
                object total = calc.ExecuteScalar();
                if (DBNull.Value.Equals(total))
                    return 0;
                else
                    return Convert.ToDecimal(total);
            }
        }
    }
}

VB:

Imports MyCompany.Data
Imports System
Imports System.Collections.Generic
Imports System.Data
Imports System.Linq
Namespace MyCompany.Rules

    Partial Public Class OrdersBusinessRules
        Inherits MyCompany.Data.BusinessRules
        Public Function CalculateOrderDetailsTotal(
                            ByRef orderID As Nullable(Of Integer)) As Decimal
            Using calc As SqlText = New SqlText(
                    "select sum(unitprice * quantity * (1 - discount)) " +
                    "from [Order Details] where OrderID=@OrderID")
                calc.AddParameter("@OrderID", orderID)
                Dim total As Object = calc.ExecuteScalar()
                If DBNull.Value.Equals(total) Then
                    Return 0
                Else
                    Return Convert.ToDecimal(total)
                End If
            End Using
        End Function
    End Class
End Namespace

This function uses SqlText utility class to create an instance of a query connected to the project’s database.
This simple query selects a sum of UnitPrice multiplied by Quantity multiplied by one minus the
Discount.

Note that SqlText utility class is generated as a part of the code base of your application. It uses the
default database connection string and ADO.NET to execute the query.

Save the file, and switch back to the application generator. Select the project name, and press Design. In the Project Explorer, switch to Controllers. Double-click on Orders / Fields / Subtotal. Make the following changes:

CalculateOrderDetailsTotal(orderID)

Press OK to save the field. The Subtotal field on the Order Form will now update to reflect any changes made to the order details.