Hierarchical development of software systems and hierarchical development of software systems

Hierarchical development of software systems and hierarchical development of software systems

1. First, you need to know what layer is?

 

A: process data. The business logic interface is displayed in different projects. Multiple projects need to be coordinated and scheduled to develop a function module. This is the core of hierarchical development.

 

2. hierarchical implementation:

 

① DAL: data access layer and data interaction, processing data (cannot be executed separately)

② BLL

③ UI: Presentation Layer: displays data

 

3. Layered steps

① Create a DAL layer and Class Library Project

② Create a UI Layer, Windows Forms

③ On the reference node of the UI Layer, right-click the first item and add a reference. A form is displayed. Select solution, check DAL, and click OK.

④ On the UI Layer, the scheduling class can be implemented through using MySchool. DAL;

 

4. Main advantages of layered architecture:

① Code reuse

② Separated developers' concerns

③ Lossless replacement

④ Reduce dependencies between systems

 

5. common Exception Handling statements include try-catch, try-finally, and try-catch-finally. The catch Block can appear multiple times, but the catch Block exception type is sorted as a subclass exception.

 

6. throws statements are used to throw an exception. In a layered architecture, the lower layer is often used to throw the exception to the upper layer.

 

☆7. Precautions (Common Errors)

① UI depends on DAL

② Set the UI Layer as a startup project

③ Do not create a form in the class library.

④ Add reference in two steps: Physical reference (right-click to add) ++ add using in the code

⑤ During the initial stage of building a layered project, you must standardize the name and do not manually change the name.

 

 

 

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