Interview prep

 In the context of dependency injection (DI) and object lifecycle management, particularly in frameworks like .NET Core, the terms Singleton , Scoped , and Transient describe different service lifetimes for dependencies. They determine how often a service instance is created and how it is shared within an application. Here’s a breakdown of each: 1. Singleton A Singleton service is created once and shared across the entire application. This single instance is created the first time it’s requested, and subsequent requests will use the same instance until the application shuts down. Usage : When you need a single, shared instance that holds state or caches data throughout the lifetime of the application. Example : Configuration settings, logging services, or any shared resource that should not be recreated frequently. Example in C#: csharp Copy code services.AddSingleton<MyService>(); Each time you inject MyService , you receive the same instance. 2. Scoped A Scoped service i...

 In C#, delegates are types that represent references to methods. They can be used to define callback methods, event handlers, and can also be used in functional programming patterns. Below is a list of commonly used delegates in C#, including built-in delegates and custom delegates. Built-in Delegates Action : Represents a delegate that can point to a method that does not return a value. It can take up to 16 parameters. Examples : Action (no parameters) Action<T> (one parameter) Action<T1, T2> (two parameters) Action<T1, T2, T3> (three parameters) ... Action<T1, T2, ..., T16> (up to 16 parameters) csharp Copy code // Example Action< string > print = message => Console.WriteLine(message); Func : Represents a delegate that can point to a method that returns a value. It can also take up to 16 parameters. Examples : Func<TResult> (no parameters) Func<T1, TResult> (one parameter) Func<T1, T2, TResult> (two parameters) Func<...

  Clean Code refers to a set of coding practices and principles aimed at writing code that is easy to read, understand, and maintain. The concept was popularized by Robert C. Martin in his book Clean Code: A Handbook of Agile Software Craftsmanship . Here are the key principles of Clean Code: 1. Readability Clear Naming : Use descriptive and meaningful names for variables, functions, classes, and other entities. Names should convey intent and be easily understandable. Consistent Formatting : Maintain consistent indentation, spacing, and formatting to improve the readability of the code. Use conventions that are standard in the programming community. Logical Structure : Organize code logically, grouping related functionality together and following a consistent structure. 2. Simplicity KISS (Keep It Simple, Stupid) : Strive for simplicity in design and implementation. Avoid unnecessary complexity and over-engineering. Each component should do one thing well. YAGNI (You Aren't Gonna ...

 Version control and Continuous Integration/Continuous Deployment (CI/CD) are fundamental practices in modern software development that enhance collaboration, maintainability, and quality of software projects. Below, we’ll explore each concept, including their principles, benefits, and key practices. Version Control Version Control is a system that records changes to files or sets of files over time, allowing developers to track and manage changes to their codebase. It facilitates collaboration among team members and provides a history of changes, making it easier to revert to previous versions if needed. Key Principles of Version Control Track Changes : Every change made to the codebase is recorded, allowing developers to see who made changes, what changes were made, and when. Branching and Merging : Developers can create branches to work on features or fixes in isolation without affecting the main codebase (usually referred to as the main or master branch). Once the work is co...

 Security principles are fundamental to ensuring the integrity, confidentiality, and availability of systems and data. Three core components of security in software systems are authentication , authorization , and encryption . Let’s explore each of these principles in detail. 1. Authentication Authentication is the process of verifying the identity of a user, device, or system. It ensures that the entity attempting to access the system is who it claims to be. Key Aspects of Authentication Methods of Authentication : Password-based Authentication : Users provide a username and password. This is the most common method but can be vulnerable to attacks if not implemented securely (e.g., weak passwords, phishing). Multi-Factor Authentication (MFA) : Requires two or more verification factors. This can include something the user knows (password), something the user has (a mobile device), or something the user is (biometrics). Token-based Authentication : After the user logs in, they rece...

 Scalability and high availability are critical principles in designing modern software architectures, particularly in distributed systems and cloud-based applications. Understanding these concepts helps ensure that applications can handle increasing loads and remain operational with minimal downtime. Below is a detailed explanation of both principles. Scalability Scalability refers to the ability of a system to handle increased loads without sacrificing performance or availability. It involves adding resources to a system to accommodate growing user demands, data volumes, or transaction rates. There are two primary types of scalability: 1. Vertical Scalability (Scale-Up) Definition : This involves adding more resources (CPU, memory, storage) to an existing server or node. Use Case : Ideal for applications that are not designed for distributed environments or require high levels of computational power. For example, upgrading a database server with more RAM to handle more queries. ...

 API design and RESTful best practices are essential for creating robust, scalable, and maintainable web services. A well-designed API facilitates easy integration and usage, while RESTful best practices ensure that the API is aligned with the principles of REST (Representational State Transfer). Below is a detailed explanation of both concepts, including key principles and best practices. API Design API design refers to the process of defining the interface and behavior of an application programming interface (API). Effective API design considers usability, performance, security, and maintainability. Here are some key aspects of API design: 1. Clarity and Consistency Naming Conventions : Use clear and descriptive names for endpoints, parameters, and data models. Follow consistent naming conventions (e.g., using camelCase or snake_case). Versioning : Implement versioning in your API (e.g., /api/v1/resource ) to manage changes without breaking existing clients. 2. HTTP Methods and S...

 The IDisposable interface in C# is implemented to provide a mechanism for releasing unmanaged resources such as file handles, database connections, or other system resources that require explicit cleanup. Here’s a brief example demonstrating how to use the IDisposable interface in a custom class, along with the recommended usage of the using statement for automatic resource management. Example: Implementing IDisposable csharp Copy code using System; public class Resource : IDisposable { // Flag to indicate whether the object has been disposed private bool disposed = false ; // Example of a resource (e.g., a file handle) private IntPtr unmanagedResource; public Resource () { // Allocate unmanaged resources unmanagedResource = /* Allocate some unmanaged resource */ ; Console.WriteLine( "Resource allocated." ); } // Implementation of the Dispose method public void Dispose () { Dispos...

 Performance optimization and memory management are critical aspects of developing efficient applications in C#. They directly influence how an application behaves, its speed, and how well it utilizes system resources. Here’s an in-depth explanation of both concepts: Performance Optimization in C# Performance optimization involves improving the speed and efficiency of a program, ensuring that it runs faster and uses resources more effectively. Here are some key strategies for optimizing performance in C#: 1. Profiling and Benchmarking Profiling : Use profiling tools (like Visual Studio Diagnostic Tools or JetBrains dotTrace) to identify performance bottlenecks in your application. Profilers can show you which methods consume the most time, memory, or other resources. Benchmarking : Measure the performance of specific parts of your code using benchmarking libraries like BenchmarkDotNet to analyze execution time and resource usage effectively. 2. Efficient Algorithms and Data Structu...

  Microservices Architecture and Service-Oriented Architecture (SOA) , along with their similarities, differences, and typical use cases. Microservices Architecture Microservices is an architectural style where applications are composed of small, independent services that communicate over a network. Each service is typically designed around a specific business function and operates as an isolated, self-contained unit. Here are some key characteristics: Independently Deployable : Each service can be developed, deployed, and scaled independently of others. Single Responsibility : Services are organized around business capabilities, such as “Order Processing” or “User Authentication.” Resilience : Each microservice operates independently, making the system more resilient since failures in one service do not necessarily impact others. Polyglot Persistence and Programming : Microservices allow for diverse technologies, frameworks, and databases across services, optimizing each service...

  Event-Driven Design is an architectural pattern where the flow of a system is driven by events, which are changes or actions that occur within the system. This approach is highly asynchronous, allowing systems to respond to events as they happen without waiting for other parts of the system to complete. It's widely used for applications requiring high responsiveness, real-time data processing, and loose coupling between components. Core Concepts in Event-Driven Design Events : An event is a significant change in state or an action that triggers a response. For example, a "user signup" or a "payment processed" can be considered events. Events are usually simple, lightweight messages containing information about what occurred (e.g., "order placed") and any relevant data (e.g., "order ID" and "user ID"). Event Producers : Producers are components that detect and create events. For instance, a user registration service would produce ...