Top 50 C# Interview Questions and Answers

Overriding Equals method helps to compare objects based on their values rather than their references.

• Default implementation of Equals method compares object references

• Overriding Equals method allows custom comparison based on object values

• Helps in implementing value equality for custom classes

• Used in collections like HashSet to check for duplicates

C# is a programming language while .NET is a framework that supports multiple languages including C#.

• C# is a programming language developed by Microsoft.

• .NET is a framework developed by Microsoft that supports multiple languages including C#.

• C# is used to write code, while .NET provides libraries and tools for building applications.

• C# code is compiled into Intermediate Language (IL) which runs on the .NET Common Language Runtime (CLR).

Yes, I know both SQL and C#.

• I have experience in writing SQL queries for database management.

• I have worked on C# projects for developing desktop and web applications.

• I am familiar with object-oriented programming concepts and database design principles.

I have completed 5 projects in C# including a web application, a desktop application, and a game.

• Developed a web application using ASP.NET MVC

• Created a desktop application for data management

• Designed a game using Unity and C# scripting

Error handling in c# involves using try-catch blocks to handle exceptions and ensure graceful handling of errors.

• Use try-catch blocks to catch exceptions and handle errors gracefully.

• Use specific exception types to catch specific errors.

• Use finally block to ensure cleanup code is executed regardless of whether an exception is thrown.

• Throw custom exceptions to provide meaningful error messages to users.

• Use logging to track and debug errors in production environments.

C# is a modern, object-oriented programming language developed by Microsoft.

• C# is used to develop Windows desktop applications, games, mobile apps, and web applications.

• It is strongly typed and supports both value and reference types.

• C# uses a syntax similar to Java and C++.

• It includes features such as garbage collection, delegates, and lambda expressions.

• C# is part of the .NET framework and can be used with other .NET languages like VB.NET and F#.

Const keyword is used to declare constants at compile time, while read-only keyword is used to create immutable fields that can only be assigned a value at runtime.

• Const values are determined at compile time and cannot be changed, while read-only values can only be assigned a value once at runtime.

• Const fields are implicitly static, while read-only fields are not.

• Example: const int x = 5; read-only int y = 10;

The '==' operator checks if two values are equal, while 'Equal' is a method that checks if two objects are equal.

• The '==' operator is used to compare values of primitive types like int, float, etc.

• The 'Equal' method is used to compare objects of reference types like string, class, etc.

• The '==' operator can be overloaded to provide custom comparison logic for user-defined types.

• Example: int a = 5; int b = 5; bool result = (a == b); // result is true

• Example: string str1 = 'hell...read more

C# is a programming language developed by Microsoft for building applications on the .NET framework.

• C# is a modern, object-oriented language with similarities to Java.

• .NET is a software framework developed by Microsoft for building and running applications.

• C# and .NET are commonly used for developing web applications, desktop applications, and mobile apps.

• C# code is compiled into Intermediate Language (IL) which runs on the Common Language Runtime (CLR) in the .NET framework.

Yes, I have used indexer extensively in my previous projects.

• I have used indexer to access elements in arrays and lists.

• I have also used it to access properties and methods of objects.

• Indexer has helped me to write more concise and readable code.

• For example, I have used indexer to access specific elements in a dictionary object.

Collection is a group of related objects of the same type that can be accessed and manipulated using methods.

• Collections are used to store, retrieve, manipulate, and communicate aggregate data.

• C# provides several built-in collection types such as List, Dictionary, Queue, Stack, etc.

• Collections can be generic or non-generic, depending on whether they are type-safe or not.

• Collections can be used to improve performance, simplify code, and enhance functionality.

Sealed class is a class that cannot be inherited or subclassed.

• Sealed classes are used to restrict inheritance for security or design reasons

• They are often used in conjunction with when expressions in Kotlin

• Example: sealed class Result

• Example: sealed class Shape

Manageable codes in dot net are codes that are easy to understand, maintain, and debug.

• Well-structured and organized code

• Proper commenting and documentation

• Consistent naming conventions

• Modular design with reusable components

• Avoiding complex nested logic

• Using design patterns for better code architecture

I work on Visual C# 2019.

• I primarily work on Visual C# 2019 for my software development projects.

• I have experience with Visual C# 2017 and earlier versions as well.

• Visual C# 2019 offers new features and improvements over previous versions.

Value types store data directly, while reference types store a reference to the data's memory location.

• Value types include primitive types like int, float, bool, struct, enum.

• Reference types include classes, interfaces, arrays, delegates.

• Value types are stored on the stack, while reference types are stored on the heap.

• Value types are copied by value, while reference types are copied by reference.

C# is a modern, object-oriented programming language developed by Microsoft.

• C# is used to develop Windows desktop applications, games, mobile apps, and web applications.

• It is a statically-typed language, meaning that variables must be declared with a specific data type.

• C# supports object-oriented programming concepts such as encapsulation, inheritance, and polymorphism.

• It also includes features such as garbage collection, exception handling, and LINQ (Language Integrated Quer...read more

A sealed class is a class that cannot be inherited or extended by other classes.

• Sealed classes are used to restrict inheritance and ensure that a class cannot have subclasses.

• They are often used when a class is considered complete and should not be extended further.

• Sealed classes can have abstract members and can be used as base classes for other classes.

• An example of a sealed class in C# is the System.String class.

The 'using' keyword in C# is used to define a scope in which an object is created and used, and automatically disposes of the object when the scope is exited.

• Used for managing resources like files, database connections, etc.

• Ensures that the object is disposed of properly even if an exception occurs.

• Example: using (FileStream fileStream = new FileStream("example.txt", FileMode.Open)) { // code }

Constants are compile-time constants, while readonly variables can be assigned a value at runtime but cannot be changed after initialization.

• Constants are declared using the 'const' keyword, while readonly variables are declared using the 'readonly' keyword.

• Constants are evaluated at compile time, while readonly variables are evaluated at runtime.

• Constants can only be assigned a value at declaration, while readonly variables can be assigned a value in the constructor.

• Constant...read more

Convert.ToString() is a static method that handles null values, while .ToString() is an instance method that may throw a NullReferenceException.

• Convert.ToString() is a static method that can handle null values and return an empty string if the input is null.

• .ToString() is an instance method that is called on an object and may throw a NullReferenceException if the object is null.

• Example: string s = null; Convert.ToString(s) will return an empty string, while s.ToString() will ...read more

The difference between configure and configure services is that configure is a general term for setting up or adjusting something, while configure services specifically refers to setting up or adjusting services.

• Configure: General term for setting up or adjusting something

• Configure services: Specifically refers to setting up or adjusting services

• Example: Configuring a computer involves setting up its hardware and software components, while configuring network services involve...read more

C# is a programming language developed by Microsoft for building a wide range of applications on the .NET framework.

• C# is widely used for developing desktop applications, web applications, mobile apps, games, and more.

• It is an object-oriented language with features like type safety, garbage collection, and scalability.

• C# is commonly used in conjunction with the .NET framework to create Windows applications.

• Examples of popular applications built with C# include Microsoft Offic...read more

ref and out are keywords in C# used for passing arguments to methods by reference.

• ref keyword is used to pass arguments by reference, allowing the method to modify the value of the argument

• out keyword is similar to ref, but the argument does not have to be initialized before being passed to the method

• Example: void UpdateValue(ref int num) { num = num * 2; }

• Example: void GetValues(out int a, out int b) { a = 10; b = 20; }

Transient creates a new instance every time it is requested, Scoped creates a new instance per scope, Singleton creates a single instance for the entire application.

• Transient: Creates a new instance every time it is requested.

• AddScoped: Creates a new instance per scope, such as per HTTP request.

• AddSingleton: Creates a single instance for the entire application.

• Example: Transient can be used for lightweight services that don't hold state, Scoped for services that need to maint...read more

Auto event wireup is a feature in ASP.NET that automatically connects events to event handlers based on naming conventions.

• Auto event wireup simplifies event handling by automatically connecting events to event handlers without needing to manually wire them up in code.

• In ASP.NET Web Forms, auto event wireup is enabled by default, but can be disabled by setting the AutoEventWireup attribute to false in the Page directive.

• Event handlers are expected to follow a specific naming ...read more

const and readonly are keywords used in programming to define variables that cannot be modified.

• const is used to declare a constant variable that cannot be changed after initialization

• readonly is used to declare a variable that can only be assigned a value at the time of declaration or in the constructor

• const variables are implicitly static and must be initialized with a constant value

• readonly variables can have different values in different instances of a class

I was rated highly in C# language due to my strong understanding of object-oriented programming principles and experience with various C# frameworks.

• Strong understanding of object-oriented programming principles

• Experience with various C# frameworks such as .NET Core, ASP.NET, and Xamarin

• Ability to write clean and efficient code

• Familiarity with C# features like LINQ, async/await, and generics

Extension methods are a way to add new methods to existing types without modifying the original type.

• Extension methods are defined as static methods in a static class.

• They must be in the same namespace as the type being extended.

• They are called like instance methods on the extended type.

• Example: Adding a method to the String class to reverse a string.

var and dynamic are both used for type inference in C#, but var is statically typed while dynamic is dynamically typed.

• var is used to declare a variable with an inferred type at compile-time.

• dynamic is used to declare a variable with a type that is resolved at runtime.

• var variables are resolved at compile-time and cannot change their type.

• dynamic variables are resolved at runtime and can change their type.

• var is mainly used for local variables, while dynamic is often used for...read more

Indexers allow objects to be indexed like arrays

• Indexers are special properties in C# that allow objects to be indexed like arrays

• They are defined using the 'this' keyword followed by square brackets containing the index parameters

• Indexers can be used to access elements in a class as if it were an array

C# 10 introduces new features like file-scoped namespaces, global using directives, and interpolated string handlers.

• File-scoped namespaces allow defining namespaces at the file level instead of wrapping everything in a namespace block.

• Global using directives simplify the process of importing namespaces across the entire project.

• Interpolated string handlers provide a way to customize how interpolated strings are processed.

Namespace in C# is a way to organize and group related classes, interfaces, structs, enums, and delegates.

• Namespaces help in avoiding naming conflicts by providing a way to uniquely identify classes.

• They also help in organizing code and making it more readable and maintainable.

• Example: using System; - System is a namespace that contains fundamental classes and base classes.

C# is a programming language developed by Microsoft for building a wide range of applications on the .NET framework.

• C# is an object-oriented language with strong typing and support for component-oriented programming.

• It is commonly used for developing Windows applications, web applications, and games.

• C# is similar to Java and C++ in syntax and structure.

• Example: C# code for a simple 'Hello World' program: Console.WriteLine('Hello, World!');

C# is a programming language developed by Microsoft for building a wide range of applications on the .NET framework.

• C# is an object-oriented language with features like classes, inheritance, and polymorphism.

• It is strongly typed, meaning variables must be declared with a specific data type.

• C# supports modern programming concepts like async/await for asynchronous programming.

• It is commonly used for developing desktop, web, and mobile applications.

• Example: C# code snippet for a...read more

Basic C# concepts include data types, variables, loops, conditional statements, classes, and methods.

• Data types in C# include int, string, bool, double, etc.

• Variables are used to store data and can be declared using var keyword.

• Loops like for, while, and do-while are used for repetitive tasks.

• Conditional statements like if-else and switch-case help in decision making.

• Classes are used to define objects with properties and methods.

• Methods contain code that performs specific tas...read more

C# 10 introduces features like file-scoped namespaces, global using directives, and interpolated string handlers.

• File-scoped namespaces allow defining namespaces at the file level instead of wrapping everything in a namespace block.

• Global using directives simplify the process of importing namespaces across the entire project.

• Interpolated string handlers enable custom processing of interpolated strings at compile time.

Yield keyword is used in C# to return a sequence of values one at a time.

• Yield keyword is used in iterator methods to return each element one by one.

• It allows the method to return multiple values without needing to store them all in memory.

• Yield return statement is used to return a value from the iterator method.

var is statically typed while dynamic is dynamically typed in C#.

• var is resolved at compile time while dynamic is resolved at runtime.

• var is used for implicitly typed local variables while dynamic is used for dynamic types.

• var cannot change its type once declared while dynamic can change its type at runtime.

Proficient in coding in C# with experience in developing various applications.

• Experienced in using C# for developing web applications, desktop applications, and APIs.

• Familiar with object-oriented programming concepts and design patterns in C#.

• Knowledgeable in using C# for database operations and integration with other technologies.

• Have worked on projects involving C# frameworks like .NET Core and ASP.NET MVC.

Lock keyword is used in C# to synchronize access to a shared resource by allowing only one thread to enter a critical section at a time.

• Used to prevent multiple threads from accessing a shared resource simultaneously

• Helps in avoiding race conditions and maintaining data integrity

• Can be used with Monitor class or lock statement

Indexers in C# allow objects to be indexed like arrays, providing a way to access elements using an index value.

• Indexers are defined using 'this' keyword followed by square brackets containing the index parameters.

• They can be used to get or set the value of an element in a collection or class.

• Example: public string this[int index] { get { return myArray[index]; } set { myArray[index] = value; }}

View lifecycle refers to the sequence of events that occur during the creation, use, and destruction of a view. Partial class is a class that is split into multiple files.

• View lifecycle includes events such as onCreate, onStart, onResume, onPause, onStop, and onDestroy

• Partial class is commonly used in C# programming language to split a large class into smaller, more manageable parts

• Partial classes can be defined in separate files, but must have the same name and be in the sam...read more

C# 9.0 introduces new features like records, init-only setters, and top-level statements.

• Records provide a concise syntax for defining immutable types.

• Init-only setters allow setting properties only during object initialization.

• Top-level statements allow writing code without a class or namespace.

• Improved pattern matching with logical patterns and relational patterns.

• Function pointers and improved support for native interop.

• New target-typed expressions and covariant returns.

• So...read more

IEnumerable is a simple interface for iterating over a collection, while IQueryable is used for querying data from a data source.

• IEnumerable is in-memory data manipulation, while IQueryable is for querying data from a database.

• IEnumerable is suitable for LINQ to Objects, while IQueryable is suitable for LINQ to SQL.

• IEnumerable is evaluated on the client-side, while IQueryable is evaluated on the database server.

• IEnumerable is more flexible but less efficient, while IQueryable...read more

Var keyword is used for implicitly typed local variables, while dynamic keyword is used for runtime type checking.

• Var is resolved at compile time, while dynamic is resolved at runtime

• Var is strongly typed, while dynamic is not

• Var is used for local variables, while dynamic is used for objects whose type is not known until runtime

C# is a powerful programming language developed by Microsoft for building applications on the .NET framework.

• C# is an object-oriented language with features like classes, inheritance, and polymorphism.

• It is widely used for developing Windows applications, web applications, and games.

• C# supports asynchronous programming with the async and await keywords.

• LINQ (Language Integrated Query) is a powerful feature in C# for querying data from various sources.

• C# is a statically typed ...read more

Access modifiers in C# control the visibility and accessibility of classes, methods, and other members within a program.

• There are five access modifiers in C#: public, private, protected, internal, and protected internal.

• Public access modifier allows a class, method, or member to be accessed from any other class.

• Private access modifier restricts access to only within the same class.

• Protected access modifier allows access within the same class or derived classes.

• Internal access...read more

Key concepts in C# include classes, objects, inheritance, polymorphism, encapsulation, and exception handling.

• Classes: Blueprint for creating objects

• Objects: Instances of classes that hold data and behavior

• Inheritance: Allows a class to inherit properties and methods from another class

• Polymorphism: Ability to use a single interface to represent different types of objects

• Encapsulation: Bundling of data and methods into a single unit

• Exception Handling: Handling and managing err...read more

Interface in C# is a reference type that defines a contract for classes to implement certain methods and properties.

• Interfaces cannot have implementation, only method signatures and properties.

• Classes can implement multiple interfaces in C#.

• Interfaces are used to achieve abstraction and multiple inheritance in C#.

• Example: public interface IShape { void Draw(); }

• Example: public class Circle : IShape { public void Draw() { Console.WriteLine("Drawing a circle"); }}