Before diving into the hands-on exercises for ASP.NET Core in this book, it’s crucial to establish the technical foundation that’s required to follow the upcoming chapters effectively. This section outlines the necessary technologies and installations you’ll need to maximize your learning experience and engage with the practical exercises provided efficiently:

• .NET 9 framework: At the core of your development environment should be the .NET 9 framework. This latest version is essential for leveraging the new and improved features offered in ASP.NET Core. It provides a comprehensive and consistent programming model that’s crucial for building high-performance web applications. Ensure that you have .NET 9 installed on your system so that you can work through the examples and projects in this book seamlessly.
• ASP.NET Core (latest version): Alongside .NET 9, having the latest version of ASP.NET Core installed is imperative. This version is specifically designed to integrate with .NET 9, offering a powerful and efficient platform for web development. It’s the framework you’ll be interacting with throughout this book, so having it updated will ensure you have access to the latest tools and features.
• Development environment: For an optimal development experience, this book recommends using either Visual Studio or Visual Studio Code, depending on your preference:
  • Visual Studio (latest version): Known for its comprehensive suite of development tools, Visual Studio is an excellent choice for ASP.NET Core development. It provides an integrated environment where you can write, debug, and deploy your applications efficiently. Ensure you have the latest version installed to benefit from the integrated support for .NET 9 and ASP.NET Core.
  • Visual Studio Code (latest version): If you prefer a lighter yet powerful editor, Visual Studio Code is your go-to option. It supports a wide range of programming languages and frameworks, including C# and .NET, making it suitable for ASP.NET Core development. With its robust ecosystem of extensions, you can tailor the editor to your specific needs, enhancing your productivity and development experience.

By preparing your environment with these technical requirements, you’ll be well-equipped to tackle the ASP.NET Core projects and examples presented in this book, ensuring a smooth and effective learning journey.

Before we start our journey into ASP.NET Core, you must understand the details of the path that you’ll be walking in this book.

ASP.NET Core stands as a groundbreaking development framework in the market for web development, offering a versatile and high-performance framework that caters to modern application needs. It has provided constant updates year after year for the last two decades. This section delves into the nature of ASP.NET Core, elucidating its core components, architectural advantages, and the benefits it brings to the development table.

ASP.NET Core is an open source, cross-platform framework for building modern, cloud-enabled, internet-connected applications. At its heart, it’s a redesign of classic ASP.NET, but with a modular, more efficient, and cross-platform runtime. This modern framework allows developers to build applications that can run on Windows, Linux, and macOS, thereby broadening the potential user base and deployment environments.

The framework’s inception was driven by the need to create a more modern web development platform that could address the evolving challenges and leverage the latest computing environments. ASP.NET Core’s architecture is lean and composable, providing developers with the flexibility to include only the necessary components in their applications. This optimizes performance and reduces resource consumption by helping them choose the correct and appropriate project templates.

Key features and architectural benefits

ASP.NET Core distinguishes itself in the web development domain with its exceptional cross-platform support, enabling developers to design and deploy applications across various operating systems, such as Windows, Linux, and macOS, without substantial code alterations. This flexibility not only expands the applications’ reach across diverse environments but also aligns with the modern trend toward platform-agnostic development, ensuring applications can cater to a wider audience, irrespective of their platform preferences.

The performance metrics of ASP.NET Core are equally impressive, showcasing significant enhancements over its forerunners. Its ability to deliver quick response times and minimize latency is crucial for applications that are expected to handle high loads efficiently. This performance edge is attributed to the framework’s optimized, lightweight architecture, which streamlines processes and reduces unnecessary overhead, ensuring applications remain agile and responsive under various operational conditions.

Modularity is another cornerstone of ASP.NET Core’s architecture, offering developers the flexibility to incorporate only the essential components needed for their applications. This not only reduces the overall size but also optimizes performance. Such modularity is invaluable for maintenance and updates, allowing for individual component enhancements without the need for broad, systemic revisions, thus keeping applications up to date and secure with minimal disruption.

Security is outstanding in ASP.NET Core, which fortifies applications with robust, built-in features safeguarding against prevalent web threats. Developers benefit from integrated support for critical security measures such as data protection, authentication, authorization, and cross-origin resource sharing (CORS) defenses, enabling them to build secure, reliable applications by default.

Integrating MVC and a Web API into a cohesive framework demonstrates ASP.NET Core’s streamlined and unified approach to web application and service development. This integration simplifies the development workflow, reducing the learning curve and fostering a more intuitive environment for developers, particularly those new to the platform.

Expanding its horizon, ASP.NET Core embraces modern web development trends with Blazor, a groundbreaking framework that allows developers to build interactive web user interfaces using C# instead of JavaScript. This innovative approach provides a seamless development experience, enabling the use of a single language across both client-side and server-side code, thus streamlining the development process and enhancing productivity.

Moreover, ASP.NET Core’s ability to integrate seamlessly with various JavaScript frameworks amplifies its versatility. This interoperability is crucial for developers leveraging the unique strengths of JavaScript frameworks such as Angular, React, and Vue.js alongside ASP.NET Core, facilitating the creation of rich, interactive, and highly responsive user experiences. The synergy between ASP.NET Core and these JavaScript ecosystems enables a more comprehensive development strategy that accommodates a wide array of project requirements and enhances the overall capability to deliver sophisticated, modern web applications.

Development experience and ecosystem

ASP.NET Core offers a superior development experience with its integration into the .NET ecosystem, providing access to a vast array of libraries and tools. Developers can leverage the powerful features of Visual Studio, Visual Studio Code, or any other editor of their choice and benefit from features such as IntelliSense, debugging, and unit testing.

The community and ecosystem around ASP.NET Core are vibrant and continuously evolving. Developers have access to a plethora of resources, including documentation, tutorials, forums, and third-party libraries, which facilitate the development process and encourage innovation.

Real-world applications and scalability

ASP.NET Core is designed to handle the demands of modern web applications, from small-scale projects to large, enterprise-level solutions. Its scalability is one of its strongest suits, enabling applications to grow in terms of users and functionality with minimal changes having to be made to the core architecture.

Companies and developers adopt ASP.NET Core for various applications, including web applications, mobile backends, IoT applications, and microservices. The framework’s versatility and performance make it suitable for a wide range of industries, including finance, healthcare, education, and e-commerce.

Continuous innovation and community support

The future of ASP.NET Core is promising, with continuous enhancements and updates being rolled out by Microsoft and the community. The framework is open source, which encourages community contributions and feedback, driving its evolution and ensuring it remains at the forefront of web development technologies.

In conclusion, ASP.NET Core is a powerful, modern framework that’s designed to meet the challenges of today’s web development landscape. Its benefits, including cross-platform support, performance, modularity, security, and scalability, make it an excellent choice for developers looking to build robust, maintainable, and efficient web applications.

Having explored the numerous advantages of utilizing ASP.NET, let’s progress to the subsequent section, where we’ll delve into the various project templates available for ASP.NET Core.

ASP.NET Core’s versatility is encapsulated in its range of project templates, each designed to cater to different web development needs. These templates not only offer a jumpstart for your projects but also integrate best practices, guiding you toward a structured and efficient development process. In this section, we’ll delve deeper into each primary template, offering a richer perspective to aid you in selecting the most fitting template for your specific project requirements.

MVC

The MVC template in ASP.NET Core serves as a robust foundation for building web applications that are scalable, maintainable, and testable. This in-depth exploration will unpack the MVC architecture, elucidating how each component operates within the framework and how this architecture facilitates a clean separation of concerns – a principle that’s vital for complex application development.

The MVC pattern is a well-established design paradigm in web application development that’s not only used by the .NET platform but by other technologies as well. ASP.NET Core’s MVC template forces the implementation of a clear pattern for web development that helps teams build complex applications while retaining simplicity and consistency in terms of software architecture. Understanding the roles and responsibilities of each component in this architectural pattern is crucial for leveraging its full potential:

• Model: In MVC, the Model represents the application’s domain. It encapsulates the data and the business rules that govern access to and modifications of this data. In ASP.NET Core, models are typically implemented as classes with properties and methods. They can include data validation rules to enforce business logic, ensuring data integrity and consistency. Models aren’t just data structures; they embody the business logic of the application, making decisions and performing calculations based on the rules defined within them.
• View: The View is responsible for rendering the user interface in an MVC application. It displays data from the model to the user and sends user commands to the controller. In ASP.NET Core, views are often created using the Razor view engine, which allows developers to write HTML with embedded C# code. Razor views are dynamic and can react to the model data they receive, enabling the creation of interactive and data-driven user interfaces. This separation of UI rendering from business logic and input handling makes the views manageable and modular.
• Controller: A Controller is a coordinator in the MVC pattern. Controllers handle user input, work with the model to perform necessary actions or calculations, and determine which view should be rendered. In ASP.NET Core, controllers are C# classes that can contain multiple actions. These actions are methods that respond to different HTTP requests, invoking changes in the model and selecting views for response. Therefore, controllers act as an intermediary, translating user inputs into actions on the model and selecting views based on the outcomes of those actions.

The MVC template is particularly advantageous for developers looking to build applications with a clear separation of concerns, thereby facilitating easier testing, maintenance, and scaling. It comes pre-configured with essential features such as routing, authentication, and authorization, allowing you to focus on developing unique application features rather than boilerplate code. This project template has the following benefits:

• Separation of concerns: By dividing the application into three interconnected components, MVC naturally promotes a clean separation of concerns. This separation enhances the maintainability of the application as developers can work on models, views, or controllers independently without significant overlap in functionality.
• Testability: The clear delineation of responsibilities in the MVC pattern facilitates more straightforward testing. Models can be tested independently of user interfaces, controllers can be tested for correct routing and response, and views can be verified to render correctly given a model. ASP.NET Core further supports this testability with features such as DI, which can be used to inject mock implementations for testing.
• Modularity and flexibility: The MVC template’s compartmentalized structure allows for modular development and flexibility. Developers can iterate on the design, presentation, and business logic layers separately, adapting to new requirements or design changes with minimal impact on the overall code base.
• A rich ecosystem and community support: Given its popularity, MVC benefits from extensive community support, a wealth of documentation, tutorials, and a plethora of libraries that can be leveraged to add functionality to your application. ASP.NET Core’s MVC framework is no exception, with strong support from Microsoft and a vibrant community, ensuring developers have access to a wealth of resources and best practices.

The MVC template in ASP.NET Core is a powerful choice for developers looking to build web applications with a proven architecture that promotes clean coding practices, testability, and separation of concerns. Its structure is conducive to developing applications that aren’t only robust and scalable but also adaptable to evolving business requirements. By understanding and utilizing the MVC architecture to its full potential, developers can create dynamic, efficient, and maintainable web applications that stand the test of time. In the next few chapters of this book, you’ll have the opportunity to experience how to create applications using the MVC architecture while following a hands-on approach.

ASP.NET Core Web API

The API project template in ASP.NET Core is meticulously designed to streamline the creation of RESTful web services. This template is a boon for developers focusing on the backend services that power web and mobile applications, IoT devices, and more. Here, we’ll delve deeper into the components and features that make the API project template a go-to choice for building high-performance and scalable APIs. The following points clarify the main features of the ASP.NET Core Web API project template:

• Foundation for RESTful services: The API project template lays the groundwork for adhering to REST principles, which emphasize stateless communication, resource identification through URIs, and the use of standard HTTP methods (GET, POST, PUT, and DELETE). This adherence simplifies the design of your API and aligns it with web standards, making it intuitive and straightforward to consume.
• Controller-based architecture: At the heart of the API template is the controller-based architecture. Controllers in ASP.NET Core serve as the entry point for handling HTTP requests and responding with data or status codes. Each controller is typically associated with a specific resource or a related group of resources, encapsulating the logic required to process incoming requests and generate responses.
• Routing and URL mapping: The API template configures routing to ensure that HTTP requests are directed to the appropriate controllers and actions. ASP.NET Core’s routing engine is capable of handling complex URL patterns and can be customized to fit the needs of your API, enabling you to define clear and descriptive routes that reflect your API’s resource hierarchy.
• Content negotiation and serialization: ASP.NET Core’s built-in support for content negotiation allows your API to serve data in various formats (such as JSON or XML) based on the client’s preferences or request headers. The framework automatically handles the serialization and deserialization of data, ensuring that your API can communicate effectively with different clients and systems.
• Model binding and validation: The API project template leverages ASP.NET Core’s model binding and validation features to streamline data processing. Model binding automatically maps data from HTTP requests to action method parameters, while applying validation attributes to your models helps ensure that incoming data meets your business rules before your application processes it.
• Error handling: Robust error handling is crucial for maintaining a reliable API. The API project template includes basic error handling mechanisms that you can extend to create a comprehensive error response strategy. This ensures that your API can gracefully handle and respond to various error conditions, providing meaningful feedback to the client.
• Testability: Just like other ASP.NET Core applications, APIs built using the API project template are highly testable. The framework’s support for DI, combined with the separation of concerns inherent in the controller-based architecture, allows you to write unit and integration tests that cover your business logic, routing, and response generation.
• Swagger integration: Developers often enhance APIs built with this template by integrating Swagger (OpenAPI), which provides interactive documentation, client SDK generation, and API discoverability. Although not included in the template by default, adding Swagger support is straightforward and significantly improves the developer experience when you’re working with your API.

By leveraging the API project template in ASP.NET Core, developers can create well-structured, performant, and scalable web services. This template not only provides the scaffolding necessary for RESTful API development but also ensures that the APIs are maintainable, testable, and compliant with industry standards, laying a solid foundation for any application’s backend services.

Razor Pages

Razor Pages, introduced in ASP.NET Core as an alternative to the MVC template, offers a streamlined approach to building web applications, emphasizing page-focused scenarios. This framework simplifies web development by integrating the server-side logic directly within the page markup, offering a more intuitive and productive way to construct dynamic web content. Let’s embark on a detailed exploration of Razor Pages, highlighting its architecture, advantages, and how it differentiates itself within the ASP.NET Core suite:

• Page-based programming model: Razor Pages centers around a page-based programming model that’s a departure from the controller and view-based MVC model. Each Razor Page is a self-contained unit consisting of a .cshtml file (which combines HTML markup with Razor syntax) and a code-behind file. This structure allows developers to encapsulate the page’s UI and business logic cohesively, promoting a high degree of modularity and maintainability.
• Code-behind model: The code-behind file in Razor Pages, typically a .cshtml.cs file, contains the server-side logic to handle user actions, data access, and other server-side operations. This separation keeps the markup clean and focused on presentation while maintaining a close association with the page’s logic. Developers can handle events, such as form submissions, directly within the page model, streamlining the development process.
• Razor syntax: Razor syntax is a powerful feature within Razor Pages that allows developers to embed C# code directly into their HTML markup. This syntax is intuitive and designed to work seamlessly with HTML, providing a robust way to dynamically generate content, control page flow, and interact with data. Razor’s syntax simplifies many common tasks, such as iterating over data collections, conditionally rendering content, and handling form inputs.
• Strongly typed data models: Razor Pages supports strongly typed data models, enabling developers to work with well-defined C# classes within their pages. This strong typing enhances code clarity, compile-time checks, and IntelliSense support in IDEs, reducing errors and improving developer productivity.
• Tag Helpers: Razor Pages leverages Tag Helpers to enable server-side code to participate in creating and rendering HTML elements in Razor files. Tag Helpers are a more readable and HTML-friendly way to define server-side logic compared to traditional MVC helpers. They can be used to easily bind form elements to data models, generate links, create forms, and more, all while maintaining a clear separation between HTML and C#.
• Routing and URL generation: Razor Pages introduces a simplified routing system that’s based on the file structure of the Pages folder. By default, the URL of a Razor Page corresponds to its location within the Pages directory. This convention-based routing reduces the complexity of defining routes and makes URL generation more intuitive.
• Built-in security features: Razor Pages come with built-in security features, such as request verification and cross-site scripting (XSS) protection, that safeguard the application against common web vulnerabilities. The framework enforces best practices such as automatically encoding output and validating request tokens to prevent CSRF attacks.
• Extensibility and customization: While Razor Pages provides a streamlined development experience out of the box, it also offers extensive options for customization and extensibility. Developers can create custom Tag Helpers, filters, and middleware to enhance functionality or integrate third-party libraries to extend the capabilities of their Razor Pages applications.

In conclusion, Razor Pages in ASP.NET Core presents a highly productive, page-focused framework for building web applications. Its integration of a UI and business logic within individual pages, support for Razor syntax and Tag Helpers, and a simplified routing model make it an attractive choice for developers seeking an alternative to the traditional MVC approach. Razor Pages strikes a balance between simplicity and power, offering a compelling model for constructing interactive, data-driven web applications.

A deep dive into Blazor Server and Blazor WebAssembly

Blazor is a groundbreaking project type in ASP.NET Core that fundamentally changes how interactive web applications can be built using the .NET ecosystem. With the introduction of .NET 9, Blazor has matured even further, offering new features and enhancements that bolster its performance, ease of development, and functionality. This deep dive explores both Blazor Server and Blazor WebAssembly, elucidating their architectures, key features, and the enhancements brought by .NET 9.

Blazor Server

Blazor Server allows you to build interactive web applications where the application logic and state management are handled on the server side. User interactions are managed through a SignalR connection, providing a robust, real-time communication channel between the client and server. The following points illuminate the key features of the Blazor Server project type and the advancements introduced in .NET 9:

• SignalR-based state management: In Blazor Server, the client’s UI state is maintained in the server’s memory. When a user interacts with the UI, the event is sent to the server over a SignalR connection and processed, after which the required UI updates are sent back to the browser. This architecture minimizes the amount of data that’s transferred over the network and leverages the server’s capabilities for heavy lifting.
• .NET 9 enhancements: With the advent of .NET 9, Blazor Server has seen improvements in performance and development experience. Enhancements in SignalR and rendering efficiencies reduce latency and improve the responsiveness of Blazor Server applications. Furthermore, improved hot reload capabilities in .NET 9 enhanced the developer experience, making UI adjustments and debugging more intuitive and faster.

Blazor WebAssembly

Blazor WebAssembly is the client-side counterpart of Blazor that enables running C# code directly in the browser using a WebAssembly-based .NET runtime. This model is akin to JavaScript frameworks but leverages the full power of .NET. The following points illuminate the key features of the Blazor WebAssembly project type and the advancements introduced in .NET 9:

• WebAssembly runtime: The Blazor WebAssembly model downloads the .NET runtime, your application, and its dependencies to the browser, executing the application directly in the browser’s sandbox. This allows for rich interactive experiences without server roundtrips, something that’s ideal for offline-capable applications, complex client-side computations, and reduced server load.
• .NET 9 enhancements: Blazor WebAssembly with .NET 9 introduces performance optimizations, smaller download sizes, and faster startup times. The runtime and tooling improvements in .NET 9 have made Blazor WebAssembly applications more efficient and quicker to load, enhancing the user experience, especially in resource-constrained environments.

Common features and improvements – Blazor Server and Blazor WebAssembly

The following are some common features and improvements that can be found in both Blazor Server and Blazor WebAssembly:

• Component model: Both Blazor Server and Blazor WebAssembly utilize a component-based architecture that promotes reusability and maintainability. Components are the building blocks of Blazor applications and encapsulate markup, logic, and styling. They can be nested, reused, and shared between projects, fostering a modular development approach.
• JavaScript interoperability: Blazor provides extensive interoperability with JavaScript, allowing developers to leverage existing JavaScript libraries and frameworks. This interoperability is crucial for accessing browser APIs not exposed through Blazor and for integrating with third-party JavaScript-based UI libraries.
• .NET 9-specific features: .NET 9 introduces more granular control over component rendering, improved error handling, and enhanced component life cycle methods. These features provide developers with more tools to optimize their applications and improve user experience.
• Mobile Blazor Bindings: With .NET 9, developers can experiment with Mobile Blazor Bindings, an exciting feature that allows Blazor components to be used to build native mobile applications using web technologies, extending the reach of Blazor beyond web browsers.
• PWA support: Blazor WebAssembly supports building progressive web applications (PWAs) out of the box. This feature enables applications to be installed on a user’s device, work offline, and leverage native device features, bridging the gap between web and native applications.

In summary, Blazor in .NET 9 continues to evolve, offering a compelling model for building web applications using C#. Whether you choose Blazor Server for its real-time capabilities and server-side processing or Blazor WebAssembly for its client-side execution and offline support, Blazor provides a robust platform for building modern web applications. The ongoing enhancements in .NET 9 further cement Blazor’s position as a versatile, performant, and developer-friendly framework in the .NET ecosystem.

Worker Service

The Worker Service template in ASP.NET Core is a versatile template that’s designed to help developers create background services for a variety of applications. These services can run in the background, executing tasks independently of user interfaces or web requests. This exhaustive overview delves into the architecture, key features, and practical applications of Worker Service templates, providing insights into how they can be utilized effectively in your .NET applications. The following points elucidate the main aspects of the Worker Service project type:

• Core architecture: At its heart, a Worker Service in ASP.NET Core is a long-running console application that leverages the generic host (HostBuilder), which is also used in ASP.NET Core web applications. This shared foundation allows for the use of familiar features such as DI, logging, and configuration systems, making it easier for developers to transition between web and worker services.
• Background task execution: The Worker Service template is ideal for executing background tasks such as processing queues, polling databases, or performing timely operations. The template provides a base class, BackgroundService, from which you can derive to implement your long-running tasks. This class offers methods such as ExecuteAsync, which you can override to define the logic of your background tasks.
• Integration with hosted services: A Worker Service template can be registered as a hosted service within the .NET Core generic host. Each hosted service can run in parallel and independently, starting and stopping together with the application. This model provides a clean abstraction for implementing different background tasks that need to run throughout the life of the application.
• DI and configuration: Utilizing the built-in DI in ASP.NET Core, Worker Service can easily access configured services and settings, enhancing its modularity and testability. Configuration values can be read from various sources, such as appsettings.json, environment variables, or command-line arguments, allowing for flexible deployment and runtime behavior.
• Logging: ASP.NET Core’s logging infrastructure is fully supported in Worker Service, enabling you to integrate robust logging mechanisms that can log to various outputs, such as the console, files, or external data stores. This is crucial for monitoring the health and performance of your background services.
• Health checks: Worker Service can implement health checks, providing insights into the health and performance of the application. This feature is especially important for services running in production as it allows for proactive monitoring and maintenance.
• Windows services and Linux daemons: One of the significant advantages of Worker Service is its ability to be hosted as Windows services or Linux daemons. This means that your Worker Service template can run automatically in the background as a system service, without requiring a user to log in.
• Containerization: Worker Service is well-suited for containerization with Docker. Running a Worker Service template in a container allows for the creation of lightweight, isolated, and scalable deployments. This is particularly beneficial in microservices architectures, where different components of the application can be deployed and scaled independently.
• Practical use cases: Worker Service can be used in a myriad of practical scenarios, such as sending batch emails, file processing, data imports/exports, or interacting with APIs for data synchronization. It’s also ideal for microservices that need to perform background work independently of user requests.

In summary, the Worker Service template in ASP.NET Core provides a robust foundation for building background services that can perform a wide range of tasks. Its integration with the broader .NET Core features, such as DI, configuration, and logging, makes it a powerful and flexible choice for developing background processes in your applications. Whether you’re processing jobs, polling resources, or performing scheduled tasks, Worker Service offers a structured yet flexible framework to build reliable and scalable background services.

Now that we understand the main aspects of the project templates available for ASP.NET Core projects, let’s move on to the next section, where we’ll explore the high-level aspects of the ASP.NET Core architecture and its features.

ASP.NET Core is a comprehensive framework designed for building modern, cloud-optimized, and internet-connected applications. Its architecture is modular, flexible, and designed to provide an optimized development framework for both web applications and APIs. Let’s delve into the ASP.NET Core architecture and its key features to understand what makes it a powerful choice for developers.

ASP.NET Core’s architecture is fundamentally modular, allowing applications to include only the necessary components and libraries, thereby reducing the application’s footprint and improving performance. This modularity is facilitated by the framework’s reliance on NuGet packages, which can be added or removed based on the specific needs of the application.

Startup and middleware in ASP.NET Core

The Startup class and middleware are foundational elements in the architecture of ASP.NET Core applications as they orchestrate the application’s behavior and its response to incoming HTTP requests. Understanding how these components interact provides insights into the backbone of ASP.NET Core’s processing pipeline.

The Startup class

The Startup class contains two main methods:

• ConfigureServices: This method is where you add and configure services needed by your application. Services such as Entity Framework Core, MVC, Razor Pages, Identity, and others are registered here. DI is a first-class citizen in ASP.NET Core, and ConfigureServices is where the DI container is populated. This method allows your application to adhere to the principle of “explicit dependencies,” ensuring that components and services declare their dependencies transparently.
• Configure: After ConfigureServices runs, ASP.NET Core calls the Configure method. This is where you build the application’s request pipeline using middleware. Each middleware component can perform operations before and after the next component in the pipeline. The order in which middleware components are added is critical and defines the order of their execution for incoming HTTP requests and outgoing responses.

Middleware

Middleware in ASP.NET Core is software that’s assembled into an application pipeline to handle requests and responses. Each piece of middleware can perform operations before passing the request on to the next component in the pipeline or performing operations before the response is sent back to the client.

The following points illustrate the main aspects of the concept of middleware in ASP.NET Core projects:

• Request pipeline: Middleware components form a chain of request delegates, where each component can perform operations asynchronously and decide whether to pass the request to the next component. If a middleware component doesn’t call the next delegate, it can short-circuit the pipeline, and no subsequent middleware is executed.
• Built-in middleware: ASP.NET Core comes with a set of built-in middleware components that you can use to enable functionality such as static file serving, routing, authentication, and session state. For example, the static files middleware serves static files and is often one of the first components in the pipeline, ensuring that requests for static files are handled without going through unnecessary processing.
• Custom middleware: You can also create custom middleware for more specific or specialized handling. Custom middleware is written by defining a class with an Invoke or InvokeAsync method that processes the HTTP request and calls the next middleware in the pipeline. This flexibility allows developers to extend the framework to suit their specific needs.
• Ordering: The order in which middleware components are added in the Configure method defines the order of their execution. This ordering is crucial because it can affect everything from security (ensuring authentication happens early in the pipeline) to functionality (ensuring MVC handling happens after the necessary preprocessing steps).
• Branching: The pipeline can be branched to configure different middleware components for different request paths. This can be achieved using the Map or MapWhen method, which provides fine-grained control over how requests are handled based on paths or conditions.

In summary, the Startup class and middleware in ASP.NET Core provide a robust and flexible way to configure how your application behaves and responds to HTTP requests. By understanding and utilizing these components effectively, developers can architect their applications to be modular, efficient, and maintainable, with clear control over the request handling pipeline.

DI in ASP.NET Core

DI is a design pattern that promotes loose coupling between components, making them more modular and testable. ASP.NET Core has built-in support for DI, allowing services to be registered and resolved throughout the application. Understanding how DI works in ASP.NET Core is crucial for developing applications that are easy to maintain and extend.

Core concepts of DI

The first concept we’ll cover is service registration. In ASP.NET Core, services are registered in the ConfigureServices method of the Startup class. This registration process maps interfaces or service types to concrete implementations. The framework provides different service lifetimes for registration, including Singleton, Scoped, and Transient, each defining how and when instances of the service are created and shared.

Now, let’s learn about service resolution. Once services have been registered, they can be injected into components, such as controllers, middleware, or other services, through their constructors. This is known as constructor injection, the most common method of DI in ASP.NET Core. The framework’s built-in DI container automatically resolves these services and their dependencies when the component is created.

In ASP.NET Core applications, services can be configured with distinct lifetimes, each defining the scope and duration of their availability within the application’s life cycle. These service lifetimes play a crucial role in determining how instances of services are created, shared, and disposed of, thereby impacting the application’s behavior, resource management, and overall architecture. The following lifetimes are available for configuration:

• Singleton: Singleton services are created once per application lifetime and shared across all requests. This lifetime is suitable for stateless services that don’t maintain any state or data specific to a request.
• Scoped: Scoped services are created once per client request (an HTTP request in the case of web applications). This is useful for services that need to maintain state or data within the context of a single request.
• Transient: Transient services are created each time they’re requested from the service container. This lifetime works well for lightweight, stateless services.

In terms of more advanced scenarios, the following configurations can be set:

• Factory-based registrations: Sometimes, more control over the creation of services is needed. ASP.NET Core allows for factory-based registrations, where you can provide a factory function to create the service. This approach is useful when the creation of the service requires more logic than simply instantiating a class.
• Property injection: While constructor injection is the recommended approach in ASP.NET Core, property injection can be achieved but requires manual intervention. It’s less preferred because it can lead to situations where dependencies aren’t initialized properly, leading to less reliable and harder-to-maintain code.
• Third-party containers: ASP.NET Core’s built-in DI container is designed to satisfy the needs of most applications. However, if you require more advanced features, the framework allows you to replace its built-in container with a third-party container, such as Autofac or StructureMap.

The following are good practices that you must follow to avoid issues when using DI and middleware in ASP.NET Core applications:

• Prefer constructor injection: Favor constructor injection over property injection for its better enforcement of dependencies, ensuring that your components are always in a valid state.
• Avoid service locator pattern: While it’s possible to use the service locator pattern by injecting IServiceProvider directly and retrieving services, this practice is discouraged as it hides a class’s dependencies, making the code harder to understand and maintain.
• Design for testability: Leverage DI to design your components to be easily testable. Mocking frameworks can be used in conjunction with DI to provide mock implementations of services when testing.
• Be mindful of captive dependencies: Ensure that you don’t inadvertently register a service with a lifetime that’s longer than the lifetimes of its dependencies. For example, a Singleton service shouldn’t depend on a Scoped service.

DI is a powerful feature of ASP.NET Core that, when used effectively, can greatly enhance the maintainability, testability, and modularity of your applications. Understanding how to properly register and resolve services, along with adhering to best practices, will allow you to fully leverage the benefits of DI in your ASP.NET Core applications.

ASP.NET Core’s architecture and features represent a significant evolution in web development frameworks, providing developers with a powerful, efficient, and flexible platform for building modern web applications and services. Whether you’re building web applications, RESTful APIs, real-time connections, or microservices, ASP.NET Core offers the tools and performance needed to create high-quality, scalable, and maintainable solutions.

Having explored details on DI and middleware for ASP.NET Core projects, let’s progress to the next section, where we’ll learn about the history of the .NET platform and ASP.NET Core.

The .NET platform, developed by Microsoft, has been a cornerstone in the evolution of software development, particularly in the web domain. Initially introduced as a beta product in 2000, .NET marked a significant milestone with its official 1.0 release in 2002 by bringing the innovative Common Language Runtime (CLR), which allowed developers to use multiple programming languages within a single solution. This feature enhanced reusability and flexibility, setting a foundation for the rich ecosystem that .NET would become.

As the platform matured, the introduction of ASP.NET provided a powerful framework for building dynamic web applications, significantly reducing the code developers needed to write. However, it was the advent of ASP.NET MVC in 2009 that marked a pivotal shift toward more structured and testable web applications. By implementing the MVC pattern, ASP.NET MVC enabled a clean separation of concerns, facilitating better maintainability and scalability of applications. This was a response to the growing complexity of web applications and the need for architectures that could support more agile development and testing practices.

Along with these advancements, the Razor syntax, introduced with ASP.NET MVC 3 in 2011, provided a more intuitive way for developers to embed server-side code within HTML. This streamlined the development process, allowing for a seamless blend of markup and C# code, and paved the way for further innovations in .NET’s approach to web development.

This evolution continued with the introduction of Razor Pages in 2017 alongside ASP.NET Core 2.0. Razor Pages simplified the web development process by offering a page-focused framework that was easier to manage and more suited for scenarios where a full MVC framework was unnecessary. This innovation brought a more approachable and efficient way to build web UIs, especially for developers who preferred a less complex structure than MVC.

A significant breakthrough in the .NET ecosystem was the launch of Blazor in 2018 with .NET Core 3.0. Blazor revolutionized web development within the .NET framework by enabling developers to use C# instead of JavaScript to create interactive client-side web UIs. This innovation allowed existing .NET skills to be leveraged for both server-side and client-side development, offering a unified and streamlined development experience. Blazor demonstrated .NET’s adaptability and its commitment to staying at the forefront of web development technologies.

Throughout its history, .NET has continuously evolved, embracing new paradigms and technologies to stay relevant in the ever-changing landscape of software development. From its initial release to the introduction of .NET and the various frameworks and syntaxes that have been added over the years, .NET has proven to be a dynamic and versatile platform. It’s catered to the needs of developers building enterprise-level applications, modern web applications, and everything in between, ensuring that .NET remains a powerful and popular choice in the software development world.

This chapter provided a comprehensive introduction to ASP.NET Core, outlining its inception, core components, and the evolution of its various frameworks and technologies. First, we went through the technical requirements for working with ASP.NET Core, recommending the .NET 9 framework and the latest version of ASP.NET Core for optimal development experience. Using Visual Studio or Visual Studio Code was recommended as the development environment to use to leverage the full range of ASP.NET Core’s features.

We began by providing an overview of ASP.NET Core as a modern, open source, cross-platform framework for building cloud-based, internet-connected applications. We emphasized the importance of understanding the framework’s architecture, functionalities, and the advantages it brings to web development.

Then, we explored the key features and benefits of ASP.NET Core, including its performance, modularity, security, and cross-platform capabilities. We also touched on the integration of MVC and the Web API, the revolutionary Blazor for building interactive web UIs with C#, and the seamless integration with various JavaScript frameworks.

Furthermore, we discussed the structure of ASP.NET Core applications, emphasizing the importance of the startup class and middleware in configuring application behavior and responses to HTTP requests. DI in ASP.NET Core was explained as a design pattern that enhances modularity and testability.

Finally, this chapter delved into the history of ASP.NET Core, tracing its development from the introduction of the .NET platform in 2000 through to innovative advancements such as ASP.NET MVC in 2009, Razor syntax in 2011, Razor Pages in 2017, and the groundbreaking Blazor in 2018. Each of these milestones was discussed in detail, highlighting how they contributed to making ASP.NET Core a versatile and powerful framework for web developers.

In the next chapter, you’ll learn how to set up and build basic applications using the project templates mentioned in this chapter. This will give you your first experience with these project types.