VB. NET data center charging system-sharpening (I)

[Self-evaluation]

The reconstruction of the data center is about to begin, and there is a mess in your mind, which is a little unprepared. I suddenly remembered the classic line "the sky does not leave any marks, but the birds have flown over" in "zhiqing ." However, I am not sure about the knowledge I have learned before, "are the birds flying over ?" Tangle!

What is "Software Engineering? The word "document" is left in the mind;

What is "UML? There are nine types of images left in your mind, which are important: use case diagram, class diagram, and sequence diagram. It is not clear how class diagrams are abstracted.

What is "Design Pattern? I only seem to remember 29 stories;

What is "three-tier architecture? Is the UI-BLL-DAL, plus Model entity class.

......

I can't express my knowledge in my own language ......

 

[Continuous cutting, micro-chaos]

The figure below is mainly about the preparation work before the reconstruction of the data center. It seems a bit messy because I am working on my own ideas. It seems like "coupling" is very high) O ~

 

 

[Learning premise]

The following describes the prerequisites for restructuring the data center:

Software Engineering

Software Engineering is to study and apply how to develop and maintain software with systematic, standardized, and quantifiable procedural methods, and how to combine time-tested and proven management technologies with the best current technical methods. It involves programming languages, databases, software development tools, system platforms, standards, and design patterns.

 

Unified UML modeling language

The Unified Modeling Language (UML) is a non-patented third-generation Modeling and specification Language. UML is an open method used to describe, visualize, build, and compile an open method for developing, object-oriented, software-intensive system products. UML presents a series of best engineering practices that have been validated for effective modeling of large-scale, complex systems, especially at the software architecture level.

1. use case diagram to describe the system functions from the user's perspective, and point out the operators of each function.

2. Static digraphs, including class diagrams, object graphs, and package diagrams.

3. Behavior diagram (Behavior digoal), which describes the dynamic model of the system and the interaction between the components. The behavior diagram includes the status diagram, activity diagram, sequence diagram, and collaborative plot.

4. Interactive digraphs: Describes the interaction between objects.

5. Implementation diagram, including the component diagram and deployment diagram

Design Mode

The design pattern is a solution proposed for various problems that are common (repeated) in software design. The design pattern is not directly used to write the code, but to describe how to solve the problem in different situations.

Object-Oriented Design Patterns generally describe the relationship and interaction between them by type or object, but do not involve specific types or objects used to complete the application. The design pattern enables instability to depend on relative stability, specific dependence on relative abstraction, avoiding complicated and tight coupling, so as to enhance the ability of software design to face and adapt to changes.

Not all software models are design models. Design Patterns refer to problems at the software "design" level. There are other non-design models, such as the architecture model. At the same time, algorithms cannot be regarded as a design model because they are mainly used to solve computing problems rather than design problems.

L3 Architecture

A three-tier architecture usually divides the entire business application into the presentation layer (UI), business logic layer (BLL), and data access layer (DAL ). The purpose of hierarchy differentiation is the idea of "high cohesion and low coupling.

DataSet

DataSet is the central concept of ADO. NET. DataSet can be regarded as a database in memory, and DataSet is an independent data set independent of the database. The so-called independence means that, even if the data link is disconnected or the database is closed, the DataSet is still available, so the DataSet can actually accommodate data with complex relationships and no longer rely on the database link. It is precisely because of DataSet that programmers can shield the differences between databases during programming to obtain a consistent programming model.

DataTable

DataTable is a virtual grid table that temporarily saves data (a table that represents data in memory .). DataTable is the core object in the ADO. NET Library. It can be applied to VB and ASP. It can simply bind a database without code. It has a Microsoft-style user interface.

Other DataTable objects include DataSet and DataView.

DataSet supports multiple tables, inter-Table relationships, and data constraints, which are basically consistent with the relational database model.

SqlHelper

SqlHelper is used to simplify the repeated Writing of database connections (SqlConnection), SqlCommand, SqlDataReader, and so on. After SqlHelper is encapsulated, you only need to input some parameters to the method, such as the database connection string and SQL parameters, to access the database, which is very convenient.

The SqlHelper class is used to encapsulate data access through a set of static methods. This class cannot be inherited or instantiated, so it is declared as a non-inherited class that contains a dedicated constructor. Each method implemented in the SqlHelper class provides a set of consistent overloading. This provides a good way to use the SqlHelper class to execute commands. It also provides necessary flexibility for developers to select a way to access data. Each method overload supports different method parameters, so developers can determine how to pass connection, transaction, and parameter information.