Datasets:
Vikhrmodels
/
programming_books_eng

Dataset card Data Studio Files
xet
Community
text
stringlengths
0
13.4k
get the user's to-do items from a database.
You could write this database code directly in the controller, but it's a
better practice to keep your code separate. Why? In a big, real-world
application, you'll have to juggle many concerns:
Rendering views and handling incoming data: this is what your
controller already does.
Performing business logic, or code and logic that's related to the
purpose and "business" of your application. In a to-do list
application, business logic means decisions like setting a default due
date on new tasks, or only displaying tasks that are incomplete.
Other examples of business logic include calculating a total cost
based on product prices and tax rates, or checking whether a player
has enough points to level up in a game.
Saving and retrieving items from a database.
Again, it's possible to do all of these things in a single, massive controller,
but that quickly becomes too hard to manage and test. Instead, it's
common to see applications split up into two, three, or more "layers" or
tiers that each handle one (and only one) concern. This helps keep the
controllers as simple as possible, and makes it easier to test and change
the business logic and database code later.
Separating your application this way is sometimes called a multi-tier or
n-tier architecture. In some cases, the tiers (layers) are isolated in
completely separate projects, but other times it just refers to how the
31
Add a service class
classes are organized and used. The important thing is thinking about
how to split your application into manageable pieces, and avoid having
controllers or bloated classes that try to do everything.
For this project, you'll use two application layers: a presentation layer
made up of the controllers and views that interact with the user, and a
service layer that contains business logic and database code. The
presentation layer already exists, so the next step is to build a service
that handles to-do business logic and saves to-do items to a database.
Most larger projects use a 3-tier architecture: a presentation layer,
a service logic layer, and a data repository layer. A repository is a
class that's only focused on database code (no business logic). In
this application, you'll combine these into a single service layer for
simplicity, but feel free to experiment with different ways of
architecting the code.
Create an interface
The C# language includes the concept of interfaces, where the definition
of an object's methods and properties is separate from the class that
actually contains the code for those methods and properties. Interfaces
make it easy to keep your classes decoupled and easy to test, as you'll
see here (and later in the Automated testing chapter). You'll use an
interface to represent the service that can interact with to-do items in
the database.
By convention, interfaces are prefixed with "I". Create a new file in the
Services directory:
Services/ITodoItemService.cs