3 layer design and multiple dataset
In 3-Layer design, we have below three layers

Presentation Layer: In this case your aspx and code behind files.

Business Layer: It seems this is missing in your project. You may include this for various purposes e.g., filtering items based on different scenarios, logged in user, etc.

Data Layer: This layer interacts with data store, external services, etc. CBLists class in this case.

Also, in OO programming class names are singular so CBLists should be changed to CBList.