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Characteristics of Modern Web Applications

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This content is an excerpt from the eBook, Architect Modern Web Applications with ASP.NET Core and Azure, available on .NET Docs or as a free downloadable PDF that can be read offline.

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"… with proper design, the features come cheaply. This approach is arduous, but continues to succeed."
- Dennis Ritchie

Modern web applications have higher user expectations and greater demands than ever before. Today's web apps are expected to be available 24/7 from anywhere in the world, and usable from virtually any device or screen size. Web applications must be secure, flexible, and scalable to meet spikes in demand. Increasingly, complex scenarios should be handled by rich user experiences built on the client using JavaScript, and communicating efficiently through web APIs.

ASP.NET Core is optimized for modern web applications and cloud-based hosting scenarios. Its modular design enables applications to depend on only those features they actually use, improving application security and performance while reducing hosting resource requirements.

Reference application: eShopOnWeb

This guidance includes a reference application, eShopOnWeb, that demonstrates some of the principles and recommendations. The application is a simple online store, which supports browsing through a catalog of shirts, coffee mugs, and other marketing items. The reference application is deliberately simple in order to make it easy to understand.

eShopOnWeb

Figure 2-1. eShopOnWeb

Reference Application

Cloud-hosted and scalable

ASP.NET Core is optimized for the cloud (public cloud, private cloud, any cloud) because it is low-memory and high-throughput. The smaller footprint of ASP.NET Core applications means you can host more of them on the same hardware, and you pay for fewer resources when using pay-as-you-go cloud hosting services. The higher-throughput means you can serve more customers from an application given the same hardware, further reducing the need to invest in servers and hosting infrastructure.

Cross platform

ASP.NET Core is cross-platform and can run on Linux, macOS, and Windows. This capability opens up many new options for both the development and deployment of apps built with ASP.NET Core. Docker containers - both Linux and Windows - can host ASP.NET Core applications, allowing them to take advantage of the benefits of containers and microservices.

Modular and loosely coupled

NuGet packages are first-class citizens in .NET Core, and ASP.NET Core apps are composed of many libraries through NuGet. This granularity of functionality helps ensure apps only depend on and deploy functionality they actually require, reducing their footprint and security vulnerability surface area.

ASP.NET Core also fully supports dependency injection, both internally and at the application level. Interfaces can have multiple implementations that can be swapped out as needed. Dependency injection allows apps to loosely couple to those interfaces, rather than specific implementations, making them easier to extend, maintain, and test.

Easily tested with automated tests

ASP.NET Core applications support unit testing, and their loose coupling and support for dependency injection makes it easy to swap infrastructure concerns with fake implementations for test purposes. ASP.NET Core also ships with a TestServer that can be used to host apps in memory. Functional tests can then make requests to this in-memory server, exercising the full application stack (including middleware, routing, model binding, filters, etc.) and receiving a response, all in a fraction of the time it would take to host the app on a real server and make requests through the network layer. These tests are especially easy to write, and valuable, for APIs, which are increasingly important in modern web applications.

Traditional and SPA behaviors supported

Traditional web applications have involved little client-side behavior, but instead have relied on the server for all navigation, queries, and updates the app might need to make. Each new operation made by the user would be translated into a new web request, with the result being a full page reload in the end user's browser. Classic Model-View-Controller (MVC) frameworks typically follow this approach, with each new request corresponding to a different controller action, which in turn would work with a model and return a view. Some individual operations on a given page might be enhanced with AJAX (Asynchronous JavaScript and XML) functionality, but the overall architecture of the app used many different MVC views and URL endpoints. In addition, ASP.NET Core MVC also supports Razor Pages, a simpler way to organize MVC-style pages.

Single Page Applications (SPAs), by contrast, involve very few dynamically generated server-side page loads (if any). Many SPAs are initialized within a static HTML file that loads the necessary JavaScript libraries to start and run the app. These apps make heavy usage of web APIs for their data needs and can provide much richer user experiences. Blazor WebAssembly provides a means of building SPAs using .NET code, which then runs in the client's browser.

Many web applications involve a combination of traditional web application behavior (typically for content) and SPAs (for interactivity). ASP.NET Core supports both MVC (Views or Page based) and web APIs in the same application, using the same set of tools and underlying framework libraries.

Simple development and deployment

ASP.NET Core applications can be written using simple text editors and command-line interfaces, or full-featured development environments like Visual Studio. Monolithic applications are typically deployed to a single endpoint. Deployments can easily be automated to occur as part of a continuous integration (CI) and continuous delivery (CD) pipeline. In addition to traditional CI/CD tools, Microsoft Azure has integrated support for git repositories and can automatically deploy updates as they are made to a specified git branch or tag. Azure DevOps provides a full-featured CI/CD build and deployment pipeline, and GitHub Actions provide another option for projects hosted there.

Traditional ASP.NET and Web Forms

In addition to ASP.NET Core, traditional ASP.NET 4.x continues to be a robust and reliable platform for building web applications. ASP.NET supports MVC and Web API development models, as well as Web Forms, which is well suited to rich page-based application development and features a rich third-party component ecosystem. Microsoft Azure has great longstanding support for ASP.NET 4.x applications, and many developers are familiar with this platform.

Blazor

Blazor is included with ASP.NET Core 3.0 and later. It provides a new mechanism for building rich interactive web client applications using Razor, C#, and ASP.NET Core. It offers another solution to consider when developing modern web applications. There are two versions of Blazor to consider: server-side and client-side.

Server-side Blazor was released in 2019 with ASP.NET Core 3.0. As its name implies, it runs on the server, rendering changes to the client document back to the browser over the network. Server-side Blazor provides a rich client experience without requiring client-side JavaScript and without requiring separate page loads for each client page interaction. Changes in the loaded page are requested from and processed by the server and then sent back to the client using SignalR.

Client-side Blazor, released in 2020, eliminates the need to render changes on the server. Instead, it leverages WebAssembly to run .NET code within the client. The client can still make API calls to the server if needed to request data, but all client-side behavior runs in the client via WebAssembly, which is already supported by all major browsers and is just a JavaScript library.

References – Modern Web Applications

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