C # Middle-layer architecture

What is a three-tier architecture:

The three-tier architecture (3-tier Application) generally divides the entire business application into: presentation layer (UI) and business logic layer (BLL) data access layer (DAL ). The purpose of hierarchy differentiation is the idea of "high cohesion and low coupling.

What are the advantages of a three-tier architecture:

1. Easy Project Modification and maintenance. During project development or after development, or even during project migration. This three-tier architecture is very convenient. For example, to migrate a project from web to form, we only need to repeat the presentation layer. The remaining two layers do not need to be changed. You only need to add them to the existing project. If this architecture is not usedCodeWrite to the presentation layer. Then almost all the codes will be re-submitted.

2. Easy to expand. This is also true for function extensions. If you want to add a function, you only need to add the method of the original class library.

3. Easy code reuse. This does not need to be explained.

4. Easy division of labor and collaboration

It can be compared to the operation of a hotel.