60+ Junior .NET Developer Interview Questions and Answers

StringBuffer is a mutable sequence of characters. It is used to efficiently manipulate strings.

• StringBuffer is a class in Java that allows you to modify strings without creating a new object.

• It is used when you need to concatenate a large number of strings efficiently.

• StringBuffer is synchronized, so it is safe to use in multi-threaded environments.

• It provides methods like append(), insert(), delete(), and reverse() to modify the string.

• Example: StringBuffer sb = new StringBu...read more

ArrayList is a dynamic array that can store objects of any type. It is used to store and manipulate collections of data.

• ArrayList is part of the System.Collections namespace in .NET.

• It can store objects of any type, including value types and reference types.

• It automatically resizes itself as elements are added or removed.

• Elements can be accessed by their index.

• It provides methods for adding, removing, and searching for elements.

• Example: ArrayList names = new ArrayList(); name...read more

Code for prime and odd numbers

• For prime numbers, check if the number is divisible by any number less than itself

• For odd numbers, check if the number is not divisible by 2

• Use loops and conditional statements to implement the checks

• Consider edge cases such as negative numbers and 0

SQL query to retrieve the maximum salary from a database

• Use the SELECT statement with the MAX function to retrieve the maximum salary

• Specify the column name for the salary field in the table

• Example: SELECT MAX(salary) FROM employees

Identifying and deleting duplicate rows in a SQL table can be done using SQL queries.

• Use the GROUP BY clause along with the COUNT() function to identify duplicate rows.

• Use the HAVING clause to filter out rows with a count greater than 1.

• Use the DELETE statement with a subquery to delete duplicate rows.

• Example: SELECT column1, column2, COUNT(*) FROM table_name GROUP BY column1, column2 HAVING COUNT(*) > 1;

• Example: DELETE FROM table_name WHERE id NOT IN (SELECT MIN(id) FROM tab...read more

Indexing in a database improves query performance by allowing faster retrieval of data.

• Indexes are used to quickly locate data without having to search every row in a table.

• Types of indexes include clustered, non-clustered, unique, and composite indexes.

• Clustered indexes physically reorder the data in the table based on the index key.

• Non-clustered indexes store a separate structure that contains the index key and a pointer to the actual data.

• Unique indexes ensure that no two ...read more

Yes, I know SQL and I am familiar with various databases.

• I have experience in writing SQL queries for Microsoft SQL Server, MySQL, and Oracle databases.

• I am familiar with database design, normalization, and indexing.

• I have worked with Entity Framework and LINQ to SQL for database access in .NET applications.

Access modifiers control the visibility and accessibility of classes, methods, and variables in programming.

• Public - accessible from anywhere

• Private - accessible only within the same class

• Protected - accessible within the same class and its subclasses

• Internal - accessible within the same assembly

• Protected Internal - accessible within the same assembly or subclasses

Key concepts of OOP include encapsulation, inheritance, polymorphism, and abstraction.

• Encapsulation: Bundling data and methods that operate on the data into a single unit (class). Example: Class with private fields and public methods.

• Inheritance: Creating new classes based on existing classes, inheriting their attributes and behaviors. Example: Subclass extending a superclass.

• Polymorphism: Objects of different classes can be treated as objects of a common superclass. Example:...read more

Procedures do not return a value, while functions return a value.

• Procedures are used to perform an action, while functions are used to calculate and return a value.

• Functions have a return type specified, while procedures do not.

• Example: Procedure to display a message on the screen vs Function to calculate the sum of two numbers.

Interfaces and abstract methods are used to achieve abstraction and provide a blueprint for classes to implement.

• Interfaces allow for multiple inheritance and provide a contract for classes to adhere to.

• Abstract methods define a method signature without implementation, allowing subclasses to provide their own implementation.

• Interfaces and abstract methods promote code reusability and maintainability.

• Interfaces can be used to achieve loose coupling and dependency injection.

• Exa...read more

Answering interview questions on finding second highest salary, OOPs concepts, and ASP.NET Core.

• To find the second highest salary, we can use the SQL query 'SELECT MAX(salary) FROM employees WHERE salary < (SELECT MAX(salary) FROM employees)'.

• OOPs concepts include inheritance, polymorphism, encapsulation, and abstraction.

• ASP.NET Core is a cross-platform, open-source framework for building modern web applications.

• The main difference between ASP.NET and ASP.NET Core is that ASP...read more

The isPostBack property is used in the Page_Load event to determine if the page is being loaded for the first time or if it is a postback.

• The isPostBack property is a boolean property that indicates whether the page is being loaded for the first time or if it is a postback.

• It is commonly used to differentiate between the initial page load and subsequent postbacks.

• This property is useful when you want to perform certain actions only on the initial page load and not on postback...read more

Dependency injection is a design pattern where components are given their dependencies rather than creating them.

• Dependency injection helps in making components loosely coupled, making it easier to test and maintain code.

• There are three main lifetimes for dependencies: transient, scoped, and singleton.

• Transient dependencies are created each time they are requested.

• Scoped dependencies are created once per request.

• Singleton dependencies are created only once and reused througho...read more

Correlated subquery refers to a subquery that depends on the outer query, while nested subquery is a subquery within another subquery.

• Correlated subquery is executed for each row of the outer query, while nested subquery is executed only once.

• Correlated subquery can reference columns from the outer query, while nested subquery cannot.

• Example of correlated subquery: SELECT * FROM table1 WHERE column1 = (SELECT MAX(column2) FROM table2 WHERE table1.id = table2.id)

• Example of nes...read more

Abstract classes can have both abstract and non-abstract methods, while interfaces can only have abstract methods.

• Abstract classes can have constructors, fields, and properties, while interfaces cannot.

• A class can inherit from only one abstract class, but can implement multiple interfaces.

• Abstract classes are used when a class needs to provide a default implementation for some methods, while interfaces are used to define a contract for classes to implement.

• Example: Abstract c...read more

CORS stands for Cross-Origin Resource Sharing, a security feature that allows servers to specify who can access their resources.

• CORS is used to prevent web pages from making requests to a different domain than the one that served the original page.

• It is implemented using HTTP headers like Access-Control-Allow-Origin.

• CORS is commonly used in web development to enable secure cross-origin requests in browsers.

• Example: If a frontend application on domain A wants to make a request...read more

Connected architecture maintains a continuous connection to the database while disconnected architecture connects only when required.

• Connected architecture is suitable for applications that require real-time data updates.

• Disconnected architecture is suitable for applications that require occasional data updates.

• Connected architecture uses DataReader while disconnected architecture uses DataSet.

• Connected architecture is faster but consumes more resources than disconnected arch...read more

AutoMapper is a library for mapping objects, middleware is software that acts as a bridge between different systems, OOPs concepts are principles of object-oriented programming.

• AutoMapper is a popular object-to-object mapping library in .NET that helps to eliminate repetitive mapping code.

• Middleware in .NET is software that can handle requests and responses between a client and a server, providing additional functionalities like logging, authentication, etc.

• OOPs concepts in ....read more

Multiple inheritance is not directly supported in C#, but can be achieved using interfaces.

• C# does not support multiple inheritance of classes due to the Diamond Problem

• Multiple inheritance can be achieved using interfaces by implementing multiple interfaces in a class

• Example: public class MyClass : Interface1, Interface2 { }

TFS and GitHub are used for version control and collaboration in software development.

• TFS and GitHub provide version control, allowing developers to track changes and collaborate on code.

• They enable multiple developers to work on the same codebase simultaneously, avoiding conflicts.

• They offer features like branching and merging, making it easier to manage different versions of code.

• TFS and GitHub provide a centralized repository for code, ensuring its availability and backup....read more

DDL and DML are SQL queries used to manipulate databases. DDL is used to create, modify or delete database objects while DML is used to manipulate data.

• DDL stands for Data Definition Language and is used to create, modify or delete database objects like tables, indexes, etc.

• DML stands for Data Manipulation Language and is used to manipulate data in the database like inserting, updating or deleting records.

• DDL queries include CREATE, ALTER and DROP statements while DML queries...read more

Code to reverse a string

• Create an empty string variable to store the reversed string

• Loop through the original string from the end to the beginning

• Append each character to the empty string variable

• Return the reversed string

substr() extracts a substring from a string based on start and length, while charindex() finds the position of a character or substring within a string.

• substr() is used in SQL Server to extract a portion of a string based on the starting position and length.

• charindex() is used in SQL Server to find the position of a specific character or substring within a string.

• Example: SELECT SUBSTRING('Hello World', 1, 5) will return 'Hello'.

• Example: SELECT CHARINDEX('o', 'Hello World') w...read more

Schema for many to many relationship

• Create a junction table to connect the two entities

• Each record in the junction table represents a relationship between the two entities

• Both entities have a many-to-many relationship with each other

Dotnet Core offers improved performance, cross-platform compatibility, and open-source flexibility.

• Improved performance compared to traditional .NET Framework

• Cross-platform compatibility allows for development on Windows, macOS, and Linux

• Open-source flexibility enables community contributions and faster updates

• Support for microservices architecture and containerization

• Enhanced security features and easier deployment options

In disconnected architecture, class names should reflect the entities or objects they represent.

• Class names should be meaningful and descriptive.

• They should follow naming conventions, such as PascalCase or camelCase.

• Avoid using abbreviations or acronyms that may not be easily understood.

• Consider using domain-specific terminology to make the class names more intuitive.

• Examples: Customer, Order, Product, Employee

I am proficient in C#, SQL, and JavaScript.

• C#

• SQL

• JavaScript

Code for Fibonacci series

• Declare two variables to store the first two numbers of the series

• Use a loop to generate the next numbers in the series by adding the previous two

• Print or store the generated numbers

Delegates are used to create references to methods and pass them as arguments to other methods.

• Delegates allow for loose coupling between objects

• Delegates can be used to implement callbacks and event handlers

• Delegates can be used to implement the observer pattern

• Delegates can be used to implement the command pattern

• Delegates can be used to implement the strategy pattern

Yes, Angular is a popular front-end framework for building web applications.

• Angular is developed and maintained by Google.

• It uses TypeScript for building applications.

• It follows the MVC (Model-View-Controller) architecture.

• It provides features like two-way data binding, dependency injection, and directives.

• Examples of popular Angular applications include Gmail, PayPal, and Upwork.

Filters in .NET are used to perform logic before or after an action method is executed.

• Filters can be used for authorization, logging, exception handling, etc.

• Examples include AuthorizeFilter, ActionFilter, ExceptionFilter, ResultFilter.

• Filters can be applied globally, at controller level, or at action level.

Abstract classes in C# provide a way to define common behavior for derived classes while allowing specific implementations.

• Use the 'abstract' keyword to define an abstract class.

• Abstract classes cannot be instantiated and can contain abstract methods that must be implemented by derived classes.

• Derived classes must provide implementations for all abstract methods.

• Abstract classes can also have non-abstract methods and properties.

• Example: abstract class Shape { public abstract ...read more

Interface defines only method signatures while abstract class can have method implementations.

• Interface cannot have method implementations, abstract class can

• A class can implement multiple interfaces but can inherit only one abstract class

• Interfaces are used for defining contracts, abstract classes are used for code reusability

• Example: Interface - ILogger { void Log(string message); } Abstract class - Shape { public abstract double CalculateArea(); }

Authentication verifies the identity of a user, while authorization determines what actions a user is allowed to perform.

• Authentication confirms the user's identity through credentials like username and password.

• Authorization controls the access rights of authenticated users to specific resources or actions.

• Example: Logging into a website with a username and password is authentication. Accessing certain pages or features based on user roles is authorization.

Join is a SQL operation that combines rows from two or more tables based on a related column between them.

• Join is used to retrieve data from multiple tables in a single query.

• Common types of joins include inner join, left join, right join, and full outer join.

• Join conditions are specified using the ON keyword followed by the columns to join on.

• Example: SELECT * FROM table1 JOIN table2 ON table1.column = table2.column;

Functions and views are used in SQL Server to encapsulate logic and simplify querying.

• Functions are reusable blocks of code that can accept parameters and return a value.

• Views are virtual tables that are based on the result set of a SELECT query.

• Functions can be scalar functions, table-valued functions, or aggregate functions.

• Views can be used to simplify complex queries by encapsulating logic and joining multiple tables.

• Functions and views can improve performance by reducing...read more

Structured Query Language

• SQL stands for Structured Query Language

• It is a standard language for accessing and manipulating databases

• Commonly used for querying, updating, and managing relational databases

• Examples include SELECT, INSERT, UPDATE, DELETE statements

Middlewares are components that handle requests and responses in the pipeline of a web application.

• Middlewares are software components that are executed in the request-response pipeline of a web application.

• They can intercept, process, or modify incoming requests and outgoing responses.

• Examples include authentication middleware, logging middleware, and error handling middleware.

Partial class is a class that can be split into multiple files, allowing different parts of the class to be defined in different files.

• Partial classes are useful for organizing large classes and separating different concerns.

• All parts of a partial class must use the 'partial' keyword.

• When compiled, all parts of a partial class are combined into a single class definition.

A class is a blueprint for creating objects, while an object is an instance of a class.

• A class defines the properties and behaviors of objects.

• An object is created based on a class, and can have its own unique values for the properties defined in the class.

• Example: Class 'Car' may have properties like 'color' and 'model', while an object of class 'Car' could be 'red Ferrari'.

Signature of multicast delegate

• A multicast delegate is a delegate that can have multiple methods assigned to it

• The signature of a multicast delegate is the same as that of a regular delegate

• The signature includes the return type, name, and parameters of the delegate

First returns the first element of a sequence, while Single returns the only element of a sequence or throws an exception if there is not exactly one element.

• First is used to retrieve the first element of a sequence, while Single is used to retrieve the only element of a sequence.

• First does not throw an exception if there are no elements in the sequence, while Single throws an exception in this case.

• Example: var numbers = new List { 1, 2, 3 }; var firstNumber = numbers.First(...read more

A function is a standalone block of code that performs a specific task, while a method is a function that is associated with a class or object.

• Functions are independent and can be called from anywhere in the code.

• Methods are associated with a class or object and are called using the dot notation.

• Functions can be defined outside of classes, while methods are defined within classes.

• Example: Function to calculate the square root of a number vs Method to calculate the area of a r...read more

ref and out are both used for passing arguments by reference in C#, but out parameters are not required to be initialized before being passed.

• ref parameters must be initialized before being passed to a method, while out parameters do not need to be initialized

• out parameters are typically used for returning multiple values from a method

• ref parameters can be used for both input and output, while out parameters are typically used for output only

A static class is a class that cannot be instantiated and is used to group related methods and properties.

• Static classes are commonly used for utility classes that contain helper methods.

• They are also used for defining extension methods.

• Example: Math class in C# contains static methods like Math.Max() and Math.Min().

SQL query and OOPs concepts are essential for a Junior .NET Developer.

• Understand SQL queries for data retrieval, manipulation, and management.

• Learn Object-Oriented Programming principles like inheritance, encapsulation, and polymorphism.

• Practice writing SQL queries to retrieve specific data from databases.

• Implement OOPs concepts in .NET applications for better code organization and reusability.