Business Rules/Logic

The following screen shows  a customer record from the Northwind sample presented in edit mode. Suppose that you want to display an action on the action bar that allows automatic calculation of certain field values.

Start the application generator and click on the project name on the start page. Select the Design option to bring up the Project Designer.

Activate the Controllers tab in Project Explorer, right-click Customers / Actions / ag4 (ActionBar) node and select New Action.

Enter the following values in the properties of the action.

Click OK button to save the action.

Press Browse on the tool bar and start editing any customer record. You will notice the Calculate Values option on the action bar.  The new action has been added to the “flat” action group ag4, which makes the action render directly on the action bar instead of being displayed as a child option of the parent action group menu item.

Clicking on Calculate Values option will close the edit form and the grid view of customers will be displayed.

You can handle a custom action in a custom business rules or shared business rules class.

Here is an example of a shared business rules class that changes Company Name and Contact Name fields.

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("Customers", "Custom", "CalcValues")]
        public void ChangeCompanyAndContactNames(string companyName, string contactName)
        {
            UpdateFieldValue("CompanyName", companyName + "+");
            UpdateFieldValue("ContactName", contactName + "-");
        }
    }
}

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("Customers", "Custom", "CalcValues")>
        Public Sub ChangeCompanyAndContactNames(ByVal companyName As String,
                                                ByVal contactName As String)
            UpdateFieldValue("CompanyName", companyName + "+")
            UpdateFieldValue("ContactName", contactName + "-")
        End Sub
    End Class
End Namespace

The implementation is invoking UpdateFieldValue method. The first argument of the method indicates the name of the data field. The seconds specifies the new value. Action “Custom” does not update the database. Any data fields changed during its execution will be packages and retuned to the client web browser. The client library of the application will replace the old values with the new ones.

Save the file ~/Rules/SharedBusinessRules.cs(vb), navigate to your application and start editing any customer record. Click Calculate Values and you will see that the characters “+” and “-” are added to the Customer Name and Contact Name fields. The record will remain in edit mode.

Business rules have complete access to the entire set of Microsoft.NET APIs.

A more complex version of the business rules class processing the same Custom action is presented next.

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("Customers", "Custom", "CalcValues")]
        public void ChangeCompanyAndContactNames(string companyName, 
            string city, string country, string customerID)
        {
            UpdateFieldValue("City", country);
            UpdateFieldValue("Country", city);
            string newCompanyName = companyName +  ": " + SqlText.ExecuteScalar(
                "select City + '/' + Country from Customers " +
                "where CustomerID = @CustomerID", customerID);
            UpdateFieldValue("CompanyName", newCompanyName);
        }
    }
}

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("Customers", "Custom", "CalcValues")>
        Public Sub ChangeCompanyAndContactNames(ByVal companyName As String,
                ByVal city As String, ByVal country As String, ByVal customerID As String)
            UpdateFieldValue("City", country)
            UpdateFieldValue("Country", city)
            Dim newCompanyName As String = companyName + ": " + SqlText.ExecuteScalar(
                "select City + '/' + Country from Customers " +
                "where CustomerID = @CustomerID", customerID)
            UpdateFieldValue("CompanyName", newCompanyName)
        End Sub
    End Class
End Namespace

This is the result of action execution if you select the customer Around the Horn, start editing the record, and click Calculate Values option on the action bar.

• Client-side values of fields City and Region are swapped and sent back to the client
• The client-side value of the field Company Name is appended with the database values of  fields City and Country.

Similar calculations can be performed without the business rules class. If you are more comfortable with SQL language and consider yourself to be a database person then learn about implementing calculations with “SQL” action.

The following screen shows  a customer record from the Northwind sample presented in edit mode. Suppose that you want to add a button to the form to automatically calculate certain field values.

Start the web application generator and select your project. Click Design to activate the Project Designer.

Activate Controllers tab in the Project Explorer and right-click Customers / Actions / ag2 (Form) node. Choose New Action option to create a new action.

Enter the following properties.

select
  @CompanyName = @CompanyName +  '+',
  @ContactName = @ContactName + '-'

Save the action and click Browse on the Designer toolbar.

Your web application will be displayed in the default web browser. Navigate to the Customers page and start editing any record.

You will notice the Calculate Values button displayed above and below the form fields. Click the button and you will see “+” added to the Company Name field and “-” added to the Contact Name field.

If you press Calculate Values button a few more times then you will see more “+” and “-” characters added to the same fields.

If you cancel the changes then the record will not be updated.

The changes made by SQL action will be persisted if you click OK button.

Action SQL causes the client library to send the current field values to the server. The core application framework knows how to handle this action.

First, the framework will find the text entered in the “Data” property of the action.

Next, it will parse the text to detect any parameters.

If you database server uses another symbol to indicate a parameter, then make sure to enter this symbol instead of “@”.

If the parameters are found then the framework will try to match them to the names of the available data fields. The application will also recognize parameters that have “_Value”, “_NewValue”, and “_OldValue” suffix. If there is a matching data field then the field’s current, new, or old value will be assigned to the parameter.

All parameters are marked as Input/Output parameters.

The application will execute the SQL text. If any parameter values have changed, then they will be packaged and sent back to the client. The client library will reflect the changed values in the user interface as if the application user has entered them in the input text boxes.

It is expected that the SQL text in action’s Data property contains instructions assigning values to parameters that are not matched to the fields. You can use any SQL language constructs supported by your database server as if you were executing them in a tool such as SQL Management Studio.

Consider the following sample data for SQL action:

declare @Temp nvarchar(50)

-- swap City and Country
set @Temp = @City
set @City= @Country
set @Country= @Temp

-- update Company Name
select @CompanyName = @CompanyName + ': ' + City + '/' + Country
from Customers 
where CustomerID = @CustomerID

Enter this text in the Data property of the action and click OK button.

This is the result of action execution if you browse to a customer record, start editing, and push the Calculate Values button.

If you need more than just an interaction with the database to perform a calculation, then consider using custom business rules or shared business rules for implementation. Learn more about implementing calculations with “Custom” action.