dotnet_interview_questions

.NET Interview Questions – Complete Study Guide

A comprehensive collection of 130 interview questions for .NET developers Covering Arrays, Lists, Trees, and General .NET / C# / SQL — with clean C# implementations, multiple solutions per problem, and full complexity analysis.

Table of Contents

• Overview
• What's Inside
• Question Categories at a Glance
• Interview Question Types
• Arrays — 20 Questions
• Lists — 20 Questions
• Trees — 20 Questions
• General .NET / C# / SQL — 70 Questions
• Repository Structure
• How to Use
• Probability of Being Asked
• Key Data Structures Comparison
• Common Algorithm Patterns
• Big-O Complexity Cheat Sheet
• Interview Tips and Strategy
• Coverage and Confidence
• Author Notes

Overview

This repository is built for .NET interview preparation and contains:

Total: 130 interview questions covering the most commonly asked topics in .NET coding interviews — from junior to mid-senior level.

What's Inside

Every coding question (Arrays, Lists, Trees) includes:

• ✅ Problem explanation in the class summary
• ✅ 2–3 solutions per problem (brute force → optimal)
• ✅ Time & space complexity analysis for each approach
• ✅ Clean, commented C# code ready to run
• ✅ Edge case discussion (empty inputs, nulls, duplicates, negatives)

The General .NET section provides:

• ✅ Detailed answers to conceptual and framework questions
• ✅ Code examples demonstrating key concepts
• ✅ Coverage of Basic → Intermediate → Advanced → Framework-Specific → Testing & Best Practices → SQL

Question Categories at a Glance

…

Interview Question Types

Understanding the types of questions you'll face helps you prepare strategically:

1. Data Structure & Algorithm (DSA) Questions

""Write a function that...""

These require you to code a solution on the spot. They test:

• Problem decomposition
• Algorithm design (brute force → optimized)
• Big-O analysis
• Edge case handling

Covered by: Arrays (20), Lists (20), Trees (20) sections

2. Conceptual / Theoretical Questions

""Explain the difference between...""

These test your understanding of language and platform fundamentals:

• Value types vs. reference types
• Abstract class vs. interface
• Managed vs. unmanaged code
• Garbage collection internals

Covered by: General .NET (Q1–Q30)

3. Framework & Architecture Questions

""How would you implement...""

These test your practical knowledge of .NET ecosystem tools:

• ASP.NET Core middleware pipeline
• Entity Framework and ORM patterns
• Dependency Injection
• SignalR, Blazor, Web API versioning

Covered by: General .NET (Q31–Q40)

4. ✅ Testing & Best Practices Questions

""How do you ensure code quality...""

These assess your engineering maturity:

• Unit testing and mocking
• SOLID principles
• Repository pattern
• CI/CD pipelines

Covered by: General .NET (Q41–Q50)

5. SQL & Database Questions

""What is the difference between...""

These test your data layer knowledge:

• JOINs, indexes, normalization
• Transactions and ACID properties
• Query optimization
• SQL injection prevention

Covered by: General .NET — SQL (Q51–Q70)

Arrays — 20 Questions

Arrays are one of the first topics in any coding interview because they test fundamental problem-solving, loops, conditions, indexes, and serve as a basis for hashing, sorting, and algorithm design.

List\ — 20 Questions

List is the most commonly used collection in .NET, offering dynamic resizing, type safety with generics, and integration with LINQ.

Trees — 20 Questions

Trees test recursive thinking, divide-and-conquer, and appear in real-world applications like file systems, org charts, and DOM trees.

Tree Node Model

All binary tree problems share a minimal TreeNode class:

public class TreeNode
{
    public int Value { get; set; }
    public TreeNode? Left { get; set; }
    public TreeNode? Right { get; set; }

    public TreeNode(int value) { Value = value; }
}

General .NET / C# / SQL — 70 Questions

These conceptual questions cover the .NET platform, C# language, ASP.NET Core framework, testing, and SQL — essential for the non-coding portion of interviews.

Basic (Q1–Q10)

Intermediate (Q11–Q20)

Advanced (Q21–Q30)