Interview Strike: React & .NET Interview Prep

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⚡ Part 1: Introduction to Generics in C#

🌍 Why Do We Need Generics? Imagine you want to create a stack (like a pile of books 📚): You can push items on top You can pop items off the top If we write a stack for integers : public class IntStack { private int[] items = new int[10]; private int index = 0; public void Push(int item) => items[index++] = item; public int Pop() => items[--index]; } 👉 Problem: This only works for int . What if we want a string stack ? Or a Customer stack ? We’d have to duplicate code for every type. 😢 ✅ Solution: Generics Generics let us create type-safe reusable code without duplication. We can say: “I don’t care what type it is yet — I’ll decide later.” 1) Generic Classes Here’s a generic stack : // Generic class "Stack<T>" // The <T> is a placeholder for any type public class Stack<T> { private T[] items = new T[10]; // Array of type T private int index = 0; // Push adds an item of type T public void P...

⚡ Part 4: Complex Scenarios with Generics in C#

In Part 1–3 , we learned: Basics of generics (methods, classes, constraints) Advanced patterns (delegates, factories, strategies) Real-world use cases (repository, service, caching, API responses) Now in Part 4 , we’ll handle trickier topics : Nested Generics Covariance & Contravariance Generic Methods in LINQ-style APIs Performance Considerations with Generics Common Pitfalls and Best Practices 1) Nested Generics Sometimes we need a generic type inside another generic type . This looks confusing at first, but it’s actually quite powerful. Example: Dictionary of Lists // A dictionary where the key is string, and the value is a list of integers Dictionary<string, List<int>> studentMarks = new(); studentMarks["Alice"] = new List<int> { 90, 85, 88 }; studentMarks["Bob"] = new List<int> { 70, 75, 80 }; foreach (var kv in studentMarks) { Console.WriteLine($"{kv.Key}: {string.Join(", ", k...

⚡ Part 3 : Real-World Use Cases of Generics in C#

in Part 3, we’ll apply generics to real-world enterprise scenarios: Generic Repository Pattern Generic Service Layer Generic Caching Utility Generic API Response Wrapper Let’s dive in 🚀 1) Generic Repository Pattern The repository pattern is used to separate data access logic (like Add , Get , Remove ) from the rest of the code. Without a generic repository, you’d write separate repositories for each entity (CustomerRepository, OrderRepository, etc.), which leads to a lot of duplicate code . Generics solve this by creating one reusable repository for all entities. Code Walkthrough // All entities will implement IEntity so that we can guarantee they have an Id property public interface IEntity { int Id { get; set; } } 👉 Why? Because in most systems, every object (Customer, Order, Product) has an Id that uniquely identifies it. By enforcing IEntity , we make sure our repository can always look up objects by Id. // Repository interface with CRUD-like operations p...

⚡ Part 2: Advanced Generics in C#

In Part 1 , we explored the basics of generics : Generic methods Generic classes Constraints Interfaces and real-world examples Now in Part 2 , we’ll dive deeper into advanced scenarios where generics really shine. We’ll cover: Generic Delegates & Events Generic Abstract Classes Generic Comparers & Equality Checkers Factory Pattern with Generics Strategy Pattern with Generics Let’s go step by step 🚀 1) Generic Delegates & Events A delegate is like a pointer to a method — it stores a reference to a function so we can call it later. When we make delegates generic , we can reuse them for multiple data types. Example: Generic Delegate // A delegate that takes two parameters of type T and returns T // This can represent operations like Add, Multiply, etc. public delegate T Operation<T>(T a, T b); class Calculator { // A generic Add method that works for numbers // Constraint: "where T : struct" ensures only...

🧱 Part 17 — Advanced TypeScript Patterns (Branded Types, Results, Exhaustive Checks) 🧠

When your app grows, types become your safety net . Here are advanced—but approachable—TypeScript patterns that prevent entire classes of bugs. Every snippet is commented and copy‑paste ready. 1) Branded (Opaque) Types — prevent mixing IDs/units Avoid passing a ProjectId where a TaskId is expected. // src/types/brand.ts // Create an opaque subtype of T (compile-time only) export type Brand<T, B extends string> = T & { readonly __brand: B }; export type TaskId = Brand<string, 'TaskId'>; export type ProjectId = Brand<string, 'ProjectId'>; export const TaskId = (s: string): TaskId => s as TaskId; export const ProjectId = (s: string): ProjectId => s as ProjectId; // Usage function loadTask(id: TaskId) {/* impl */} // loadTask('123'); // ❌ plain string not allowed loadTask(TaskId('123')); // ✅ branded Brands exist only at compile time; runtime values are plain strings. 2) Discriminated Unions + Exhaustiv...

🧱 Part 16 — Accessibility First (Semantics, Keyboard, ARIA, Focus, Color)

Accessibility (a11y) is not optional : it helps keyboard users, screen‑reader users, and frankly everyone (think: low contrast screens, bright sun, fatigue). This part is beginner‑friendly and packed with commented patterns you can paste in today. 🎯 Goals Semantic HTML & landmarks (nav, main, header, footer) Keyboard support (Tab order, focus outlines, ESC to close) Visible focus with :focus-visible Skip link , visually hidden text, live regions Readable colors (contrast), reduced motion ARIA for dialog , tabs , and form errors 1) Baseline: semantic layout + skip link Make the structure obvious to assistive tech and provide a quick jump to content. // src/app/Layout.tsx import { SkipLink } from '@/components/a11y/SkipLink'; export default function Layout({ children }: { children: React.ReactNode }) { return ( <div> <SkipLink target="#main" /> <header role="banner" className="p-4 border-b...