70+ 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

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

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

To implement a recursive query in SQL, use Common Table Expressions (CTE) with a recursive part and a termination condition.

• Use a Common Table Expression (CTE) to define the recursive part of the query.

• Include a base case in the CTE to stop the recursion.

• Reference the CTE in the main query to retrieve the results.

• Example: WITH RecursiveCTE AS (SELECT * FROM TableName WHERE condition UNION ALL SELECT * FROM RecursiveCTE WHERE condition)

Generics in .NET allow you to create reusable code that can work with different types.

• Generics are declared using the 'generic' keyword followed by the type parameter(s) in angle brackets.

• Example: 'public class MyGenericClass<T> {}'

• You can use multiple type parameters separated by commas.

• Example: 'public class MyGenericClass<T1, T2> {}'

• Generics provide type safety and eliminate the need for casting.

• Example: 'List<string> myList = new List<string>();'

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

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.

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

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

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

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

Class names for a chess game using OOP concepts include pieces, board, and game logic components.

• ChessBoard: Represents the chessboard with an 8x8 grid.

• ChessPiece: Base class for all chess pieces (e.g., Pawn, Rook, Knight).

• Pawn: Inherits from ChessPiece, defines movement and capture rules.

• Rook: Inherits from ChessPiece, defines vertical and horizontal movement.

• Game: Manages the game state, player turns, and rules enforcement.

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

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

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