added more to the net core section

Author: rcallaby

CORE/Introduction.md

@@ -0,0 +1,26 @@
+# Summary: .NET Core Interview Questions in the Context of C# Development
+
+When preparing for a C# technical interview, a solid understanding of .NET Core is essential. As the modern, cross-platform successor to the traditional .NET Framework, .NET Core plays a foundational role in contemporary C# application development. It is now part of the unified platform known simply as **.NET** (from .NET 5 onward), which consolidates .NET Core, .NET Framework, and Xamarin under a single development model.
+
+The core distinction between **.NET Core** and the **.NET Framework** lies in flexibility, performance, and cross-platform capabilities. Unlike the Windows-only .NET Framework, .NET Core is platform-agnostic and open-source, allowing developers to build and deploy applications across Windows, macOS, and Linux. Understanding these differences is critical during interviews, especially for backend or full-stack roles involving ASP.NET Core.
+
+Many interview questions aim to explore a candidate’s knowledge of these core differences. For instance, one foundational question focuses on **.NET Core vs. .NET Standard**. .NET Standard is not a runtime but a specification that ensures compatibility across .NET implementations, such as .NET Framework and .NET Core. Candidates are expected to demonstrate when and why to target one over the other—typically choosing .NET Core for active development and .NET Standard for libraries intended to be shared across runtimes.
+
+Another important concept is the **dependency injection (DI)** model in .NET Core, which is built into the framework by default. In contrast to .NET Framework, where DI must be manually integrated via third-party libraries like Autofac or Unity, .NET Core simplifies service management through its built-in `IServiceCollection` and `IServiceProvider`. This feature is central to ASP.NET Core and is often assessed in architectural or design-pattern questions.
+
+Middleware is another topic where .NET Core differentiates itself. Unlike the old pipeline model of HttpModules and HttpHandlers in the .NET Framework, **middleware in .NET Core** is modular, composable, and linear. Candidates are frequently asked to describe how middleware components are used in the request pipeline to manage tasks like logging, authentication, and routing.
+
+Understanding how .NET Core manages **cross-platform runtime behavior** is also essential. The runtime uses Runtime Identifiers (RIDs) and supports deployment via portable and self-contained models. Candidates may be asked to explain the **CoreCLR runtime**, which supports Just-In-Time (JIT) and Ahead-of-Time (AOT) compilation and provides better performance and resource usage compared to the older CLR in .NET Framework.
+
+Modern ASP.NET Core applications use `appsettings.json` and environment variables for configuration, replacing the rigid and centralized `web.config`. This decoupled configuration system, along with dependency injection, gives developers fine-grained control over environment-specific behavior.
+
+From a performance perspective, .NET Core includes significant enhancements in memory management, garbage collection, and startup performance. The garbage collector (GC) in CoreCLR has been optimized for server-side performance, offering features like background GC and workstation GC modes.
+
+Interviewers also often assess familiarity with performance-focused features like `Span<T>` and `Memory<T>`, which enable low-allocation, high-performance memory access—especially relevant in high-throughput systems like APIs or real-time applications.
+
+Additionally, a candidate may be asked to explain the role of **`IHostedService`** and background services in .NET Core, which are used for long-running tasks outside the context of a request/response lifecycle. This is particularly important in microservice architectures or systems that require scheduled processing.
+
+The shift from **IIS to Kestrel** as the default web server in ASP.NET Core is another noteworthy topic. Kestrel is lightweight, high-performance, and cross-platform. Candidates are expected to understand how it can be used alone or with a reverse proxy like IIS or Nginx for enhanced security and load balancing.
+
+In summary, these interview questions collectively probe a candidate's understanding of the architecture, tooling, and philosophy behind modern .NET Core and C# development. A strong grasp of these concepts not only demonstrates technical competency but also shows readiness for modern enterprise application development in the evolving .NET ecosystem.
+

README.md

@@ -24,6 +24,7 @@ Preparing for a technical interview for a C# role is a crucial step in landing a
 + [Abstract Classes](https://github.com/rcallaby/CSharp-Interview-Questions/blob/main/Abstract-Classes/Introduction.md)
 + [Sealed Classes](https://github.com/rcallaby/CSharp-Interview-Questions/blob/main/Sealed-Classes/Introduction.md)
 + [Clean Code](https://github.com/rcallaby/CSharp-Interview-Questions/blob/main/Clean-Code/Introduction.md)
+* [CORE]
 + [Design Patterns](https://github.com/rcallaby/CSharp-Interview-Questions/blob/main/Design-Patterns/Introduction.md)
 + [SOLID Code](https://github.com/rcallaby/CSharp-Interview-Questions/blob/main/SOLID-Code/Introduction.md)
 + [Unit Tests](https://github.com/rcallaby/CSharp-Interview-Questions/blob/main/Unit-Tests/Introduction.md)