3-Tier Architecture in asp.net using c# 3-Tier architecture consists of 1) UI or Presentation Layer 2) Business Access Layer or Business Logic Layer 3) Data Access Layer Presentation Layer Presentation layer consists of pages like .aspx or desktop based form where data is presented to users or getting input from users. Business Logic layer or Business Access Layer Business logic layer contains all of the business logic. Its responsibility is to validate the business rules of the component and communicating with the Data Access Layer. Business Logic Layer is the class in which we write functions that get data from Presentation Layer and send that data to database through Data Access Layer.