.NET/C# Interview Masterclass- Top 500 Questions (PDF)(2026)

discover the difference between c sharp and dot net, where c sharp is an object oriented language running on the dot net framework, with clr, framework class libraries, and assemblies.

Identify the limitations of OOP concepts in small applications, highlighting the need for planning and time when implementing inheritance, and balancing OOP ideals with execution and delivery.

Learn how classes and objects work in C sharp, where a class acts as a blueprint with fields, properties, methods, and a constructor, and objects are the in-memory instances.

Define a property as a class member that provides a flexible mechanism to read and write private fields, and enforce encapsulation by avoiding direct field access.

Understand how namespaces act as containers for related classes and other types, and learn to import and access classes such as stringbuilder from system.text.

Learn how inheritance creates a parent-child relationship that lets a derived class automatically reuse base class methods, improving code reusability and avoiding duplication.

Explore the different types of inheritance in c#, including single, multiple (via interfaces), multi-level, and hierarchical inheritance, with base and derived classes.

Explain how to prevent inheritance in C# by using sealed on a base class, contrast with using static for non-inheritable classes, and note that sealed allows objects while static cannot.

Explain that private class members are not inherited by derived classes. Note that only public and protected members can be inherited.

Explore method overloading in C# as a form of polymorphism, where same-name methods perform different tasks. Learn three overloads: different parameter counts, types, and orders.

Learn when to use method overloading in real projects to cover scenarios without proliferating unique method names, using examples like add and string substr overloads.

Explore the difference between method overloading and method overriding using base and derived classes, virtual and override keywords, and runtime versus compile-time polymorphism.

Explain the difference between abstraction and abstract class, noting that abstraction shows only required details while hiding background ones, and that an abstract class is one way to implement abstraction.

In C# you cannot declare abstract methods as private; abstract methods are only declarations and must be implemented by derived classes, otherwise a compiler error.

Explore how boxing and unboxing impact performance, why integer-to-object and object-to-integer conversions slow down execution, and why using a generic list is preferable unless necessary.

Use StringBuilder when you need to change a string multiple times to boost performance and avoid creating new strings; use string for infrequent updates, since it is lightweight.

Compare continue and break in loop control: continue transfers control to the loop start, skipping the rest of the iteration, while break exits the loop, showing 0,1,2 under continue.

Use the finally block to reliably dispose resources, such as closing a SQL connection, ensuring the connection closes whether an error occurs and improving performance by avoiding garbage collection delay.

Explore C# generics and collections through nine interview-style questions, covering array, list, hash table, dictionary, and differences questions, with a focus on enumerable and enumerator concepts, in about 18 minutes.

Explore collections in C#, their types and categories—normal, concurrent (thread-safe), and generic—along with examples like ArrayList, hash table, dictionary, List, Queue, and Stack.

Compare the difference between array and array list in .NET using code: arrays are strongly typed and fixed in size, while array lists store any type of item through boxing.

Compare array list and hash table by highlighting that array list stores values only, while hash table maps keys to values, enabling direct retrieval via keys.

Explore how IEnumerable enables for-each iteration in C# by using a list of employees; see how List derives from IEnumerable to support enumeration.

Compare enumerable and enumerator in C# by highlighting foreach-based iteration versus explicit GetEnumerator and MoveNext, and see how enumerable simplifies using the enumerator.

Compare IEnumerable and IQueryable in C#, noting that IQueryable inherits from IEnumerable and enables server-side filtering for SQL queries, improving performance by filtering at the database rather than loading data.

Explore constructors in c# through 12 concise questions, covering different constructor types in an easy-to-understand, eight-minute session.

Explore the types of constructors in C# — default, parameterized, copy, static, and private constructors, with step-by-step explanations.

Learn how a default constructor in .NET is automatically created by the compiler when no other constructors exist, and why defining a parameterized constructor prevents this default from being generated.

Understand how a parameterized constructor accepts at least one parameter and prints the x parameter value, as shown with x equals 100.

Explore the static constructor in C# and its real-world use: it runs before any static member and before calling static methods via the class name, without object creation.

Discover why static constructors cannot have parameters or access modifiers in C#, as explained in the lecture.

Learn what a private constructor does: it prevents inheritance and object creation, suits classes with only static members, and enables the singleton pattern.

Explain why you cannot instantiate or inherit a class with a private constructor in C#, and how a private constructor prevents object creation.

Explain that when creating a derived object, the base class constructor fires first, then the derived constructor, clarifying the constructor call order in C#.

Explain the difference between pass by value and pass by reference parameters using code examples, clarifying how the ref keyword alters variable addresses and outcomes.

Learn how extension methods add new functionality to existing classes without modifying source code. Explore static classes and this binding, with examples like a right substring extension.

Learn how multicast delegates in C# hold references to more than one function and invoke them in sequence, enabling multiple methods like add and multiply to run.

Discover how anonymous delegates in C# reference methods without names by providing the method body inline within the delegate declaration, i.e., an anonymous method.

The this keyword refers to the current instance of a class and distinguishes class fields from constructor parameters, preventing naming confusion between this.id and id.

Explain how the is operator checks an object's type and returns a boolean, while the as operator converts compatible reference types, not yielding a boolean.

Explain the static class as a container for static members only, with no object creation or inheritance. Learn when to use it to access static methods via the class name.

Explore why you cannot inherit an enum in C#. Enums are sealed class types, producing a compile time error when inheritance is attempted, and coding related concepts aid understanding.

Explore the yield keyword in C# and learn how yield return turns a get even numbers routine into a streaming iterator that generates values on the fly for efficiency.