What is a three-layer structure in asp.net

One or three-tier architecture

1. Presentation layer (USL): The main means of the web way, can also be expressed as a WinForm way. If the logic layer is very strong and perfect, the logic layer can provide services perfectly regardless of how the presentation layer is defined and changed.

2. Business Logic Layer (BLL): Mainly for the operation of specific problems, can also be understood as the operation of the data layer, the data business logic processing. If the data layer is a building block, the logic layer is the building of these blocks.

3. Data access Layer (DAL): Mainly to the original data (database or text files, such as the form of data storage), rather than the original data, that is, the operation of the data, rather than the database, specifically for the business logic layer or presentation layer to provide data services.

Ii. Specific Distinctions

1. Presentation layer: The primary acceptance of the user's request, as well as the return of the data, providing the client with access to the application.

2. Business Logic Layer: mainly responsible for the operation of the data layer, that is, some data-tier operations are combined.

3. Data access layer: Mainly look at your data layer contains no logical processing, in fact, his functions mainly complete the operation of the data file, without the need for other operations.

Third, summary

A three-tier structure is a rigorous layered approach, that is, the data access layer can only be accessed by the business logic layer, the business logic layer can only be accessed by the presentation layer, the user transmits the request to the business logic layer through the presentation layer, the business logic layer completes the relevant business rules and logic, and accesses the database through the data access layer to obtain data Then, in reverse order, return the data to the presentation layer