10 posts tagged with "ASP-NET-CORE"

Motivation​

Suppose you work on ASP.NET Core web application that solves some business-related tasks. You know, a few forms where users enter their data and get some reports. Although such a project may not require any complex logic on the client, you still probably need to write some JavaScript code to make user interaction with your application more convenient and enjoyable. For example, you may need a simple prompt popup on item deletion since it's not quite right to use a separate page for that. Or, you want to do client-side validation. Or ... it really can be any other client-side task, you name it.

Introduction​

There are many ways to create a web application today. We have a lot of different platforms, frameworks, and libraries: PHP, Python, Java, NodeJS, and a dozen of others.

While ASP.NET (Core) was always a good choice for developing enterprise-level web applications (with many complex web pages, some Web API endpoints, static resources, etc.), it's never been the best choice for creating a small web service with just a few endpoints to handle REST API requests in JSON or plain text formats.

Well, that was true until .NET 5 was released last year. With support for top-level statements and new features in C# language, .NET 5 allows us to create a solid web service in just a few minutes and with a single code file.

Implementing CRUD operations in your ASP.NET Core application can be a very tedious and time-consuming task. EasyData helps to add all necessary functionality (and even more) in a matter of minutes.

Problem​

One of the first tasks for most business applications is to implement CRUD (Create, Read, Update, Delete) operations for the main entities the app works with.

Every developer faces the following problems as part of solving the task:

• The creation of CRUD pages and forms is very boring and time-consuming. Believe me, I’ve been there a lot of times.

• If you do it manually, it can be very slow and error-prone (missed fields, forgotten validators, etc).

• Of course, you can use the scaffolding tool provided by Visual Studio. However, it’s also not a quick process either, because you need to run that tool for each model class. As a result, you get many .cs and .cshtml files, which you'll have to edit manually if something in the default behavior or appearance doesn't suit your needs. In the event of changes in the model classes, you'll need to update those generated controllers and pages manually or regenerate the code and forms from scratch for each affected model class.

• Moreover, even the built-in scaffolding doesn't provide some important, often essential functions such as paging or search.

This is the second part of the article, where we take apart the default ASP.NET Core solution template piece by piece and try to explain the purpose of each part and how exactly it works. You can consider it as a reference where you can check why a particular part was added to your project and find a link to the relevant documentation that explains it in detail.

Startup class​

As we already mentioned in the first article, the Startup class is the entry point for all initialization codes in your application. Long story short, the Startup defines what your application will do and how exactly it will work.

Introduction​

When you start learning a programming language, one of your first exercises will probably be to write a “Hello World” application to figure out the basic concepts. This exercise works well if you’re writing a simple console program that will only print out the greetings on the screen.

However, once you move onto learning to write web apps using a new framework, such as ASP.NET Core, such a simple code is not enough — partially because web apps are more complex. And also because, right off the bat, the tools and frameworks used for writing web apps try to introduce advanced techniques and approaches for building and maintaining them once they scale.

It all can seem like too much for a beginner. Here we will take apart the default ASP.NET Core solution template piece by piece, then figure out the purpose of each piece and how exactly it works.

Please note that this isn’t a full-scale tutorial on all the aspects of creating web apps in ASP.NET Core. Rather, it is a short guide where you can check why a particular part is added to your project or find a piece of code and a link to the relevant documentation that explains it in detail.

As an example, I used a new solution that targets .NET 5. However, most of this article's information will also be relevant for the ASP.NET Core projects that target .NET Core 3.1 or the upcoming .NET 6.

Creating a New Web Project​

Let’s start with creating a new empty web app with the “Create a new project” wizard in Visual Studio.

Here is how this step should look:

When you press Next, the wizard will ask you to choose the names of the new solution and project and the folder to place the solution files in:

Tip #1: Place the project and the solution into separate folders. Choosing the same location for both is convenient only for very small applications. Once you start adding other layers to your solution (domain classes, data layers, API, etc.), having them in separate projects will be more practical.

Tip #2: Use the general name of your application for the name of the solution (like “MyCoolApp”) and add the “.Web” suffix for the project name (e.g., “MyCoolApp.Web”).

Project Structure​

After finishing the steps described above, you will get a new solution with one project inside it.

The structure of that project will look similar (or even the same) to the following one:

Let’s take a closer look at each part of your new project.

1. Connected Services​

This is the first node in your project’s structure and possibly the less-used one. It is intended to automate the multiple steps necessary to connect a project to an external service (like Azure Storage or Application Insights). You can right-click on this node and select “Add connected service…” to run a wizard that will lead you through the process. Usually, it just adds necessary packages and gives you basic instructions on how to start using your app's service. As I’ve already mentioned, there is a good chance you will not use this node during your project’s lifetime.

2. Dependencies​

This element of your project structure contains all packets or other projects on which your project depends.

There are four main folders inside this node:

• Analyzers
  They help you make your code better: cleaner, error-free. Each analyzer checks that your code satisfies a list of rules incorporated in it. If any part of your code does not apply to one of the rules, you will see either a Warning or an Error while you build your project.

Please note that analyzers work only at compile time and do not affect your resulting application.

• Frameworks
  This folder contains a list of frameworks your project depends on. This information is important if you publish your web app as a runtime-dependent (as opposed to a self-contained one). In this case, all the frameworks listed here must be installed on the server where you will run your app.

NB: You can use dotnet --info console command to check the list of installed frameworks.*

• Packages
  This is the main item in this node. It lists all NuGet packages you added (installed) to your project. If any of those packages depend on other packages, they will be installed automatically and listed as sub-nodes of the root-level packages. You can remove each installed package here (right-click / Remove).

• Projects
  This is the list of other projects in this solution your current project depends on. You can reference other projects using the “Add reference” command from the right-click menu. Obviously, this node is empty now since we have only one project in the solution.

3. Properties​

This part contains different properties of your project that you can modify by double-clicking on this node in the Solution Explorer. Most of the properties there affect the compile- and debug-time behavior of your project.

The only item inside this node is a “launchSettings.json” file containing the launch profiles. Each profile defines how to run your project when you click on the “Run” button in Visual Studio.

4. wwwroot​

This folder contains all the static files of your web application: CSS files, JavaScript files, images, and icons. As you might figure out from its name, this will be the root folder of your web app. So if you put an “image1.png” file into the “wwwroot/images/dir1” folder, it will be accessible in the browser by the “/images/dir/image1.png” address.

5. Areas​

This folder is added because we selected the “Individual Accounts” value for the “Authentication Type” option when created the project.

In addition to the core authentication/authorization packages (which is called ASP.NET Core Identity), the default template also adds the “Microsoft.AspNetCore.Identity.UI” package. This is a Razor-class library that contains all forms and partial views for authentication and user management: Login, Registration, Reset Password, User Profile, and many others. All these forms will use your layout (defined in Pages/Shared/_Layout.cshtml) and so will match your website’s design.

However, you still might want to change some of those forms (or even all of them). In this case, you can use the Scaffold command and add the necessary files to your project. The scaffolded files will be added to the Areas/Identity folder.

6. Data​

As in the previous case, this folder appears in our new project because of the “Authentication Type” option that was turned on at the beginning.

By default, all user-related information (users, their roles, claims, etc.) is stored in a database accessed with Entity Framework Core ORM (object-relational mapping) framework. If you are not familiar with EF Core, you can find a lot of tutorials on Microsoft Docs.

The “Data” folder contains your DB context class named “ApplicationDbContext.” This class is derived from the “IdentityDbContext” class defined in the “Microsoft.AspNetCore.Identity.EntityFrameworkCore” assembly, and it includes all DB sets (tables) necessary to store user-related information.

You can use this class or create another DbContext class to add your models.

Additionally, the “Data” folder also includes “Migrations” sub-folder with all your Entity Framework Core migrations.

7. Pages​

This folder contains all pages (forms) of your web applications. ASP.NET Core has two default approaches for content rendering: MVC (Model View Controller) and Razor Pages (which is, actually, a kind of MVC, where each controller and the corresponding view are stored together). Both approaches use Razor syntax that you can think of as HTML + C#.

Each Razor page is represented by a “.cshtml” file. The code related to it is stored in a so-called “code-behind” file with the same name and a “.cshtml.cs” extension.

From the start, the “Pages” folder contains a few default pages, such as Index (the home page of your web app), Privacy, and Error. Additionally, you can find the main layout file (_Layout.cshtml) and some partial views in the “Pages/Shared” folder.

NB: It’s a common practice to prefix the names of the layouts and partial views with _ symbol.

8. Root Folder Files​

Now, when we’ve looked over all the main folders created with the default ASP.NET Core application template, let’s take a closer look at the files stored in the project’s root folder. They are the most important part of the project.

Program.cs​

This file defines the “Program” class with one static method, “Main,” which is the entry point of your web application.

The only purpose of this method is to define the host and then pass the control to the Startup class. For more information about the default host builder, look at an article about Generic Host on Microsoft’s Docs.

application.settings​

This is a JSON file that stores the application’s settings. The settings have a hierarchical structure and can be accessed with the Configuration object defined in the Startup class or in any other place of your program where you injected IConfiguration service. For example:

var defaultLogLevel = Configuration.GetValue<string>("Logging:LogLevel:Default");

The different levels of hierarchy are separated by the colon (:) symbol.

By default, in addition to “application.settings”, the ASP.NET Core template also includes an “application.Development.settings” file. The settings defined in this file are loaded only into the Development environment and are not available in production. To learn more about the “.settings” files and configuration in ASP.NET Core projects in general, please read this article on Microsoft’s Docs.

Startup.cs​

This is the final part of the ASP.NET Core project’s structure. The “Startup” class serves three main purposes:

• It performs all initialization tasks (setting application-wide constants, DB seeding, migrations, etc.).

• It registers all services used in this project in the DI (dependency injection) container.

• It defines the middleware pipeline of your web-application.

This class contains a lot of code (as for a project that has just been created) from the beginning and will become even bigger when you start adding new features to your application.

We will take a look at it in more detail in the next article.

Introduction​

This is a second edition of the previous post on the same topic. The reason why I wrote this one is because of some drastic changes made in ASP.NET Core Authentication system from version 2.0 to version 2.2 - so most of the code presented in the first article doesn't work with the new version.

So, the code in the following articles was built for and tested with ASP.NET Core 2.2. The main concept, however, is still the same and were not changed since ASP.NET Identity 2.0 (I guess).

As in the previous case, we will start with a description of the problem.

Problem​

Sometimes, when you build a multi-tenant web-application you may need to set up a "master password" to your system - the password which allows some administrator to login to any user's account. Something similar to su command in Unix/Linux systems.

This is a third part of the series of articles about some not-so-well-known features and tricks in ASP.NET Identity. Here are you can find the first and the second parts.

Problem​

This task usually appears when you need to transfer your old MVC web application to ASP.NET Core. If you use MVC version 3 or 4 and your application provides a user authentication service, then most likely this part is done with the old ASP.NET Membership library.

So, imagine you have a bunch of users, each of them has some password and the hash of that password stored in some database. Now you need to transfer all your current users to the new system built with ASP.NET Core. Of course, it's not a big problem to transfer their names, addresses, and other information. The problem is in those password hashes. ASP.NET Core Identity uses another hashing algorithm so all current users will not be able to access the system with their old passwords - the hashes will not match.

This is the second article in a series of articles about ASP.NET Core Identity. You can find the first one here.

Problem​

Let's suppose you created a new ASP.NET Core with the default Authentication (like in previous article). Then you run it and try to register a new user. On the registration form, we need to enter a password. Since we need to register a user for testing purposes first of all - we don't want to make the password too complicated. We'd prefer to keep it simple and easy-to-remember (in the end - it's not a production-mode system!)

However, if you try to enter something simple like "qwerty" or your name - you will get the following bunch of error messages:

• Passwords must have at least one non-alphanumeric character.
• Passwords must have at least one digit ('0'-'9').
• Passwords must have at least one uppercase ('A'-'Z').

The reason for all these validation errors is that by default ASP.NET Core Identity has very strong password policies for the users. In the error messages above you can see the constraints which must be satisfied.

NB: The solution presented in this article will work in version 2.0 of ASP.NET Core only!
If you use a newer version of ASP.NET Core (e.g. 2.2) - here is a new post on the same topic.

Introduction​

With this post, we start a series of articles that describe the different aspects of using ASP.NET Identity in your ASP.NET (Core) applications. All the code in the following articles was built for and tested with ASP.NET Core 2.0. However, in most cases, it will work well in earlier versions of .NET framework (4.x) and ASP.NET Identity library (2.x)

One more note. We are NOT going to do an introduction to or describe the basic principles of ASP.NET Core in general or APS.NET Identity in particular. The following material is more for the developers who already have some experience with both of them. If you don't - please start by reading the tutorials on ASP.NET Core documentation website and creating your first web app with it.