Decoupling Business Logic Layer from the User Interface Layer using C#
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by Joydip Kanjilal
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Decoupling the User Interface Layer from the Business Logic Layer

Now, once a Business Logic and a Business Entity instance is created via the BusinessLogicObjectFactory and the BusinessEntityObjectFactory classes respectively, the exposed public properties of the BusinessService class, namely BusinessLogic and BusinessEntity, are used to set the business logic and the business entity instances created using the factory classes mentioned above. This is done in the presentation layer or the user interface layer of the application.

The following code snippet shows how you can use the BusinessService class to decouple the business logic from the user interface layer of your application using dependency injection technique.

Listing 11

IBusinessLogic iBusinessLogic = BLFactory.GetBLObject(BLObjectType.Employee);
IBusinessEntity iBusinessEntity = BEFactory.GetBEObject(BEObjectType.Employee);
//Code to populate the business entity instance with data
BusinessService businessService = new BusinessService();
businessService.BusinessLogic = iBusinessLogic;
businessService.BusinessEntity = iBusinessEntity;
businessService.Execute(OperationType.Create);

Note how the factory classes have been used to create the business logic and the business entity instances respectively. The static methods GetBLObject and GetBEObject accept references of the BLObjectType and BEObjectType enumerators. These methods then check the corresponding values and return business logic or business entity instances appropriately. Refer to the code shown in the listing 7 and 8 above. You can create instances of the DepartmentBO or the DepartmentDO by simply changing the binding as shown below.

Listing 12

IBusinessLogic iBusinessLogic = BLFactory.GetBLObject(BLObjectType.Department);
IBusinessEntity iBusinessEntity = BEFactory.GetBEObject(BEObjectType.Department);
//Code to populate the business entity instance with data
BusinessService businessService = new BusinessService();
businessService.BusinessLogic = iBusinessLogic;
businessService.BusinessEntity = iBusinessEntity;
businessService.Execute(OperationType.Create);

We can make the decoupling even more efficient (more loosely coupled) using a XML file where we can store the binding information. The binding information here implies the information that relates a user interface to its business logic and business entity classes.

Then we can use the factory classes to create the business logic or business entity instances as illustrated below.

Listing 13

IBusinessLogic iBusinessLogic = BLFactory.GetBLObject
    (ConfigurationManager.GetBLObjectName(“U001”));
IBusinessEntity iBusinessEntity = BEFactory.GetBEObject
    (ConfigurationManager.GetBEObjectName(“U001”));
//Code to populate the business entity instance with data
BusinessService businessService = new BusinessService();
businessService.BusinessLogic = iBusinessLogic;
businessService.BusinessEntity = iBusinessEntity;
businessService.Execute(OperationType.Create);

In the above code example, notice that we have used a class called ConfigurationManager to read the binding information from a XML file. The methods GetBLObjectName and GetBEObjectName return the names of the business logic and the business entity classes respectively. These methods accept the screen ID as parameters and use this ID to search and retrieve the binding information from the XML file that contains it.

We are done! I leave it to the readers to design the XML schema that relates a user interface to its corresponding business logic or business entity class name. Then you have to implement a class that reads this binding information; you can name it as ConfigurationManager.


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