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ASP.NET Core 2 Fundamentals
ASP.NET Core 2 Fundamentals

ASP.NET Core 2 Fundamentals: Build cross-platform apps and dynamic web services with this server-side web application framework

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Profile Icon Gumus Profile Icon T. S. Ragupathi
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Paperback Aug 2018 298 pages 1st Edition
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Arrow left icon
Profile Icon Gumus Profile Icon T. S. Ragupathi
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€29.99
Paperback Aug 2018 298 pages 1st Edition
eBook
€15.99 €23.99
Paperback
€29.99
Subscription
Free Trial
Renews at €18.99p/m
eBook
€15.99 €23.99
Paperback
€29.99
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Renews at €18.99p/m

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ASP.NET Core 2 Fundamentals

Controllers

In the previous chapter, we discussed that all web applications receive requests from the server and produce a response that is delivered back to the end user. This chapter covers the role of controllers in ASP.NET MVC applications and details the procedure of creating a controller and action methods. 

By the end of this chapter, you will be able to:

  • Explain the role of the controller in ASP.NET MVC applications
  • Work with the routing engine
  • Install the ASP.NET Core NuGet packages in your application
  • Create your first controller and action methods
  • Add a view and make the changes that allow your controller to use that view
  • Add a model and pass that model data to your view

Role of the Controller in ASP.NET MVC Applications

A controller does the job of receiving the request and producing the output based on the input data in ASP.NET MVC. You can imagine controllers as the entrance point to your business flow that organizes the application flow.

If you are intending to write a complex application, it is best to avoid business logic in your controllers. Instead, your controllers should call your business logic. In this way, you can keep the core part of your business technology-agnostic.

At the high level, the controller orchestrates between the model and the view, and sends the output back to the user. This is also the place where authentication is usually done through action filters. Action filters are basically interceptors and will be discussed in detail in the Filters section of this chapter. The following diagram illustrates the high-level flow...

Introduction to Routing

The routing engine is responsible for getting the incoming request and routing that request to the appropriate controller based on the URL pattern. We can configure the routing engine so that it can choose the appropriate controller based on the relevant information. In other words, routing is a programmatic mapping that states which method of which controller is to be invoked based on some URL pattern.

By convention, ASP.NET MVC follows this pattern: Controller/Action/Id.

If the user types the URL http://yourwebsite.com/Hello/Greeting/1, the routing engine selects the Hello controller class and Greeting action method within the Hello controller, and passes the Id value as 1. XXXController is a naming convention and it is assumed your controllers are always ending with a controller suffix. You can give default values to some of the parameters and make some...

Installing the ASP.NET Core NuGet Package in Your Application

We'll straight away jump to installing the ASP.NET Core NuGet package in your application.

Follow these steps to install the NuGet package of ASP.NET MVC:

  1. Right-click on the dependencies, and select the Manage NuGet Packages option:

  1. We will see that a package called Microsoft.ASPNetCore.All is installed (as shown in the following screenshot). This package is actually a meta package that installs most of the dependencies we need.

  1. If we extend this package from dependencies, we will see:

So, everything we need is already installed regardless of using an empty project or not.

ASP.NET Core is installed in our application. Now, we need to tell our application to use ASP.NET MVC.

This needs a couple of changes to the Startup.cs file:

  1. Configure the application to add the MVC service. This can be done by adding...

Our First Controller

Before creating the controller, we need to remove the following app.Run statement as this will return Hello World! for all the incoming requests. As we want incoming requests to be handled by the controllers, we need to remove the following code from the Configure method of the Startup class:

app.Run(async (context) =>
{
await context.Response.WriteAsync("Hello World!");
};

We have installed ASP.NET Core in our application. So, we are geared up for creating our first ASP.NET Core controller. Create a folder with the name Controllers and add a new controller from the context menu, as shown in the following screenshot:

Context basically represents the request-response pair along with other metadata necessary to process the request. 

For people who used OWIN to develop your own web custom framework without using MVC, it is analogous...

Adding Views

So far, we were returning a simple string from the controller. Although that explains the concept of how the Controller and action methods works, it is not of much practical use.

Let's create a new action method named, Index2:


Go to https://goo.gl/UhaHyz to access the code.
public IActionResult Index2()
{
return View(); // View for this 'Index2' action method
}

Now, we have created the action method that returns a view, but we have still not added the view. By convention, ASP.NET MVC would try to search for our view in the Views\{ControllerName}\{ActionMethod.cshtml} folder. With respect to the preceding example, it will try to search for Views\Home\Index2.cshtml. Please note that the name of the controller folder is Home, not HomeController. The prefix is only needed as per convention. As this folder structure and file are not available, you&apos...

Adding Models

Models represent your business domain classes. Now, we are going to learn about how to use the Models in our controller. Create a Models folder and add a simple Employee class. This is a just a plain old C# class:


Go to https://goo.gl/uBtpw3 to access the code.
public class Employee
{
public int EmployeeId { get; set; }
public string Name { get; set; }
public string Designation { get; set; }
}

Create a new action method, Employee, in our HomeController, and create an object of the Employee Model with some values, and pass the Model to the View. Our idea is to use the Model employee values in the View to present them to the user:


Go to https://goo.gl/r4Jc9x to access the code.
public IActionResult Employee()
{
//Sample Model - Usually this comes from database
Employee emp1 = new Employee
{
EmployeeId = 1,
Name = "Jon Skeet",
Designation = ...

Role of the Controller in ASP.NET MVC Applications


A controller does the job of receiving the request and producing the output based on the input data in ASP.NET MVC. You can imagine controllers as the entrance point to your business flow that organizes the application flow.

Note

If you are intending to write a complex application, it is best to avoid business logic in your controllers. Instead, your controllers should call your business logic. In this way, you can keep the core part of your business technology-agnostic.

At the high level, the controller orchestrates between the model and the view, and sends the output back to the user. This is also the place where authentication is usually done through action filters. Action filters are basically interceptors and will be discussed in detail in the Filters section of this chapter. The following diagram illustrates the high-level flow of a request (with the steps) in ASP.NET MVC and shows us how the controller fits into the big picture:

The following...

Introduction to Routing


The routing engine is responsible for getting the incoming request and routing that request to the appropriate controller based on the URL pattern. We can configure the routing engine so that it can choose the appropriate controller based on the relevant information. In other words, routing is a programmatic mapping that states which method of which controller is to be invoked based on some URL pattern.

By convention, ASP.NET MVC follows this pattern: Controller/Action/Id.

If the user types the URL http://yourwebsite.com/Hello/Greeting/1, the routing engine selects the Hello controller class and Greeting action method within the Hello controller, and passes the Id value as 1. XXXController is a naming convention and it is assumed your controllers are always ending with a controller suffix. You can give default values to some of the parameters and make some of the parameters optional.

The following is the sample configuration:

The template: "{controller=Hello}/{action...

Installing the ASP.NET Core NuGet Package in Your Application


We'll straight away jump to installing the ASP.NET Core NuGet package in your application.

Follow these steps to install the NuGet package of ASP.NET MVC:

  1. Right-click on the dependencies, and select the Manage NuGet Packages option:
  1. We will see that a package called Microsoft.ASPNetCore.All is installed (as shown in the following screenshot). This package is actually a meta package that installs most of the dependencies we need.
  1. If we extend this package from dependencies, we will see:

So, everything we need is already installed regardless of using an empty project or not.

ASP.NET Core is installed in our application. Now, we need to tell our application to use ASP.NET MVC.

This needs a couple of changes to the Startup.cs file:

  1. Configure the application to add the MVC service. This can be done by adding the following line to the ConfigureServices method of the Startup class:

Note

Go to https://goo.gl/RPXUaw to access the code.

public void...
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Key benefits

  • Adopts the application-centric approach to explain core concepts
  • Covers industry-best practices to build flexible, robust applications
  • Shows how to enhance your applications by adding more functionalities

Description

The book sets the stage with an introduction to web applications and helps you build an understanding of the tried-and-true MVC architecture. You learn all about views, from what is the Razor view engine to tagging helpers. You gain insight into what models are, how to bind them, and how to migrate database using the correct model. As you get comfortable with the world of ASP.NET, you learn about validation and routing. You also learn the advanced concepts, such as designing Rest Buy (a RESTful shopping cart application), creating entities for it, and creating EF context and migrations. By the time you are done reading the book, you will be able to optimally use ASP.NET to develop, unit test, and deploy applications like a pro.

Who is this book for?

If you are looking to build web applications using ASP.NET Core or you want to become a pro in building web applications using the Microsoft technology, this is the ideal book for you. Prior exposure and understanding of C#, JavaScript, HTML, and CSS syntax is assumed.

What you will learn

  • Work with basic programming constructs using the Razor view engine
  • Use flexibility and data compartmentalization of ViewModel
  • Build a custom route for ASP.NET MVC applications for SEO
  • Optimize applications with performance analysis and improvement steps
  • Improve application performance, security, and data access to optimize the overall development process
  • Deploy an ASP.NET MVC application in a non-Windows environment
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Publication date : Aug 30, 2018
Length: 298 pages
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Length: 298 pages
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ISBN-13 : 9781789538915
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Table of Contents

9 Chapters
Setting the Stage Chevron down icon Chevron up icon
Controllers Chevron down icon Chevron up icon
Views Chevron down icon Chevron up icon
Models Chevron down icon Chevron up icon
Validation Chevron down icon Chevron up icon
Routing Chevron down icon Chevron up icon
Rest Buy Chevron down icon Chevron up icon
Adding Features, Testing, and Deployment Chevron down icon Chevron up icon
Other Books You May Enjoy Chevron down icon Chevron up icon
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