Interview Roadmap | DotNetInterviews

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OOPS

Build a strong foundation in object-oriented design.

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What is OOPS and why is it useful?

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What is the difference between a class and an object?

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What is inheritance and which types does C# support?

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What is polymorphism? Compare overloading and overriding.

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Explain abstraction and encapsulation with a practical example.

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When should you use an interface instead of an abstract class?

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What is method overloading and how does it differ from method overriding?

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What are constructors and destructors in C#?

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SOLID Principles

Practice the design principles that keep object-oriented code maintainable.

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What are the SOLID principles and why do they matter?

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What is the Single Responsibility Principle?

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How does the Open/Closed Principle guide extension and modification?

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What is the Liskov Substitution Principle?

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How does the Interface Segregation Principle improve interfaces?

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What is Dependency Inversion and how does dependency injection support it?

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C# Fundamentals

Review the language features that appear in everyday interviews.

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What is the difference between value types and reference types?

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What is the difference between ref, out, and in parameters?

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How do async and await work in C#?

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What is IDisposable and how does the using statement help?

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What is boxing and unboxing in C#?

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What is the difference between var, dynamic, and object in C#?

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What is LINQ and how is it used in C#?

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What are the differences between IEnumerable, ICollection, IList, and IQueryable?

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What are the differences between structs and records in C#?

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What are attributes and how does reflection work in C#?

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What is the difference between const, readonly, and static in C#?

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What is the purpose of the using statement in C#?

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What are generics in C# and how do they improve type safety?

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What is the difference between throw and throw expressions in C#?

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What is the difference between synchronous and asynchronous programming in C#?

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ASP.NET Core

Understand how web applications are composed and served.

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How does the ASP.NET Core request pipeline work?

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Explain dependency injection lifetimes: transient, scoped, and singleton.

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What is middleware and how do you write custom middleware?

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How do authentication and authorization differ?

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What are different types of exception handling in ASP.NET Core?

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How does garbage collection work in .NET?

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How does logging work in ASP.NET Core?

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How does ASP.NET Core work with IIS?

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What is Kestrel and how does it serve requests?

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How do cookies and sessions work in ASP.NET Core?

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What are caching strategies in ASP.NET Core?

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What is the difference between Dispose and Finalize in ASP.NET Core?

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SQL and Entity Framework

Practice data access, queries, and performance fundamentals.

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What is Entity Framework Core and how does it work?

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What is DbContext and how does it manage database connections?

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What is DbSet and how does it represent a table in EF Core?

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What is the difference between lazy loading and eager loading in EF Core?

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What is the difference between tracking and no-tracking queries in EF Core?

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How does LINQ work with Entity Framework Core?

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What is change tracking in Entity Framework Core?

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What are stored procedures, views, and functions in SQL?

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What are primary, unique, and foreign keys in SQL?

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What is the difference between DELETE, DROP, and TRUNCATE in SQL?

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What are transaction isolation levels in SQL?

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What is the difference between SQL and NoSQL databases?

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What is the difference between VARCHAR and NVARCHAR in SQL?

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What is the difference between UNION and UNION ALL in SQL?

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Explain the common SQL joins and when to use them.

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What is an index and when can it hurt performance?

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What is a deadlock in SQL and how can it be resolved?

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What does ACID stand for in database transactions?

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What are triggers in SQL and when should they be used?

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Web API and System Design

Connect backend concepts to resilient, maintainable services.

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What are the common HTTP methods and when should they be used?

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What are common HTTP headers used in REST APIs?

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What is CORS and how does it affect API requests?

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What is the difference between authentication and authorization in APIs?

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Which HTTP status codes should an API return for common outcomes?

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What are practical approaches to API versioning?

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How would you design caching for a read-heavy service?

How would you scale a .NET API as traffic grows?