C# Interview Questions
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August 26, 2026
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C# Interview Questions
Prepare for C# interviews with practical, concept-based and scenario-oriented questions. Each answer can be expanded without leaving the page.
Topics covered: C# Basics, OOPs, Collections, Exception Handling, Advanced C#, LINQ, Async/Await and practical scenarios.
C# Basics Interview Questions
Answer:
C# is a modern, object-oriented and type-safe programming language developed by Microsoft. It is commonly used with the .NET platform for building desktop, web, API, cloud and other applications.
C# is a modern, object-oriented and type-safe programming language developed by Microsoft. It is commonly used with the .NET platform for building desktop, web, API, cloud and other applications.
Interview Tip: Mention that C# is
object-oriented, strongly typed and commonly used with .NET.
Answer:
Important features include object-oriented programming, strong type checking, automatic memory management through garbage collection, exception handling, generics, delegates, LINQ and asynchronous programming.
Important features include object-oriented programming, strong type checking, automatic memory management through garbage collection, exception handling, generics, delegates, LINQ and asynchronous programming.
Interview Tip: Give 3–5 features and
briefly explain one rather than only listing names.
Answer:
C# is a programming language, while .NET is a development platform and runtime ecosystem that provides libraries, runtime services and tools for executing applications written in C# and other languages.
C# is a programming language, while .NET is a development platform and runtime ecosystem that provides libraries, runtime services and tools for executing applications written in C# and other languages.
Answer:
CLR stands for Common Language Runtime. It provides runtime services such as memory management, garbage collection, exception handling and execution support for managed .NET applications.
CLR stands for Common Language Runtime. It provides runtime services such as memory management, garbage collection, exception handling and execution support for managed .NET applications.
Answer:
Managed code is code executed under the control of the .NET runtime. The runtime manages services such as memory allocation, garbage collection and exception handling.
Managed code is code executed under the control of the .NET runtime. The runtime manages services such as memory allocation, garbage collection and exception handling.
Answer:
Value types directly contain their data, while reference types contain a reference to an object. Examples of value types include int, bool and struct; class, array and string are reference types.
Value types directly contain their data, while reference types contain a reference to an object. Examples of value types include int, bool and struct; class, array and string are reference types.
Answer:
Boxing converts a value type to object or another compatible reference type. Unboxing extracts the value type from the boxed object and requires a compatible type.
Boxing converts a value type to object or another compatible reference type. Unboxing extracts the value type from the boxed object and requires a compatible type.
int number = 10;
object obj = number; // Boxing
int value = (int)obj; // Unboxing
Answer:
var is resolved at compile time and still has a specific
type. dynamic defers member/type checking to runtime.
object is the base type of the .NET type system and may
require casting to use a specific value.
Answer:
A namespace logically groups related types and helps avoid naming conflicts between classes, interfaces and other types.
A namespace logically groups related types and helps avoid naming conflicts between classes, interfaces and other types.
Answer:
A class is a blueprint that defines data and behavior through fields, properties, methods, constructors and other members. Objects are instances of classes.
A class is a blueprint that defines data and behavior through fields, properties, methods, constructors and other members. Objects are instances of classes.
Answer:
An object is an instance of a class. It has state represented by data and behavior represented by methods.
An object is an instance of a class. It has state represented by data and behavior represented by methods.
Answer:
A constructor is a special member used to initialize an object when it is created. It has the same name as the class and does not have a return type.
A constructor is a special member used to initialize an object when it is created. It has the same name as the class and does not have a return type.
Answer:
Yes. Constructor overloading allows a class to have multiple constructors with different parameter lists.
Yes. Constructor overloading allows a class to have multiple constructors with different parameter lists.
Answer:
A
A
const value must be assigned at declaration and is
constant at compile time. A readonly field can be
assigned at declaration or in a constructor and is then not normally
assignable afterward.
Answer:
A static member belongs to the type itself rather than to an individual object. It can be accessed using the class name.
A static member belongs to the type itself rather than to an individual object. It can be accessed using the class name.
Answer:
Access modifiers control the visibility of types and members. Common modifiers include public, private, protected and internal.
Access modifiers control the visibility of types and members. Common modifiers include public, private, protected and internal.
Answer:
Method overloading means defining multiple methods with the same name but different parameter lists. It is compile-time polymorphism.
Method overloading means defining multiple methods with the same name but different parameter lists. It is compile-time polymorphism.
Answer:
Method overriding allows a derived class to provide a new implementation for an inherited virtual or abstract member.
Method overriding allows a derived class to provide a new implementation for an inherited virtual or abstract member.
Answer:
An interface defines a contract that implementing types agree to follow. It is commonly used to achieve abstraction and loose coupling.
An interface defines a contract that implementing types agree to follow. It is commonly used to achieve abstraction and loose coupling.
Answer:
An abstract class is a class intended to be used as a base class. It can contain implemented members as well as abstract members that derived classes must implement.
An abstract class is a class intended to be used as a base class. It can contain implemented members as well as abstract members that derived classes must implement.
Answer:
An abstract class can provide shared implementation and state, while an interface primarily defines a contract. A class can implement multiple interfaces, while class inheritance has a single direct base class.
An abstract class can provide shared implementation and state, while an interface primarily defines a contract. A class can implement multiple interfaces, while class inheritance has a single direct base class.
Answer:
A sealed class cannot be inherited. It is useful when a type's implementation should not be extended through inheritance.
A sealed class cannot be inherited. It is useful when a type's implementation should not be extended through inheritance.
Answer:
A struct is a value type that can contain fields, properties, methods and constructors. It is commonly useful for small values where value semantics are appropriate.
A struct is a value type that can contain fields, properties, methods and constructors. It is commonly useful for small values where value semantics are appropriate.
Answer:
An enum defines a set of named integral constants, making code easier to read when a value can belong to a fixed set of choices.
An enum defines a set of named integral constants, making code easier to read when a value can belong to a fixed set of choices.
Answer:
A nullable value type allows a value type to also represent null. For example,
A nullable value type allows a value type to also represent null. For example,
int? can contain an integer or null.
Answer:
A string object cannot be modified after it is created. Operations that appear to change a string create another string object.
A string object cannot be modified after it is created. Operations that appear to change a string create another string object.
Answer:
String is immutable, so repeated modifications can create multiple objects. StringBuilder is mutable and is generally more suitable when many string modifications are required.
String is immutable, so repeated modifications can create multiple objects. StringBuilder is mutable and is generally more suitable when many string modifications are required.
Answer:
Garbage collection automatically identifies objects that are no longer reachable and reclaims their managed memory.
Garbage collection automatically identifies objects that are no longer reachable and reclaims their managed memory.
Interview Tip: Do not describe GC
as immediately freeing every object after it goes out of scope.
Answer:
IDisposable provides a standard pattern for explicitly releasing resources such as file handles, database connections or other unmanaged resources held by an object.
IDisposable provides a standard pattern for explicitly releasing resources such as file handles, database connections or other unmanaged resources held by an object.
Answer:
The using statement is commonly used with IDisposable resources so that Dispose is called automatically when execution leaves the scope.
The using statement is commonly used with IDisposable resources so that Dispose is called automatically when execution leaves the scope.
using (var connection = CreateConnection())
{
connection.Open();
}