20+ Interview Questions and Answers

Enable JWT Authentication in ASP Core Web API with Roles

• Install the required NuGet packages like Microsoft.AspNetCore.Authentication.JwtBearer

• Configure JWT authentication in Startup.cs file

• Add authentication middleware in Configure method

• Implement role-based authorization using policies and attributes

I have 3 years of experience as an ASP Core Web API and ReactJs Developer.

• 3 years of experience in ASP Core Web API development

• Proficient in ReactJs development

• Developed multiple projects using ASP Core Web API and ReactJs

Use indexing, limit the columns retrieved, optimize queries, use pagination

• Create indexes on columns frequently used in queries

• Limit the columns retrieved to only those needed

• Optimize queries by using WHERE clauses and avoiding SELECT *

• Implement pagination to retrieve records in smaller chunks

Context API is a built-in feature in React for managing global state, while Redux is a standalone library for state management.

• Context API is built into React, while Redux is a separate library.

• Context API is primarily used for managing global state in a React application.

• Redux provides a centralized store for managing state across the application.

• Context API is simpler to use for smaller applications, while Redux is more suitable for complex state management needs.

• Redux allo...read more

Joins are used to combine rows from two or more tables based on a related column, while subqueries are nested queries used to return data for the main query.

• Joins are used to retrieve data from multiple tables based on a related column

• Subqueries are nested queries within a main query to return data for the main query

• Joins are typically more efficient than subqueries for large datasets

• Joins can be of different types like INNER JOIN, LEFT JOIN, RIGHT JOIN, etc.

• Subqueries can be...read more

Views are virtual tables, procedures are reusable code blocks, functions return values

• Views are virtual tables that display data from one or more tables

• Procedures are reusable code blocks that can be called multiple times

• Functions return a single value based on input parameters

• Views are read-only, while procedures and functions can modify data

• Examples: View - SELECT * FROM employees_view; Procedure - EXECUTE get_employee_details(101); Function - SELECT calculate_salary(101);

Key features of ASP Dot Net CORE include cross-platform support, high performance, and modularity.

• Cross-platform support allows developers to build and run applications on Windows, macOS, and Linux.

• High performance achieved through features like a new lightweight and modular HTTP request pipeline.

• Modularity enables developers to include only the necessary components in their applications, reducing the overall size and improving performance.

• Support for cloud-based applications...read more

Dependency Injection is a design pattern where the dependencies of an object are provided externally rather than created within the object itself.

• Dependencies are injected into a class through constructor injection, setter injection, or interface injection.

• This helps in achieving loose coupling between classes and makes the code more testable and maintainable.

• Example: Instead of creating an instance of a dependency within a class, the dependency is passed to the class from ou...read more

Code First: Develop database from code. Database First: Generate code from existing database.

• Code First: Focus on code design and then generate database schema.

• Database First: Focus on existing database schema and generate code classes.

• Code First: More control over database design and relationships.

• Database First: Faster development for existing databases.

• Code First: Entity Framework Code First approach.

• Database First: Entity Framework Database First approach.

To connect SQL to ASP Core Web API, you need to configure a database connection in the API project.

• Configure a connection string in the appsettings.json file of the API project.

• Install Entity Framework Core package in the API project.

• Create a DbContext class that inherits from DbContext and represents the database.

• Use dependency injection to inject the DbContext into the API controllers.

iOS design patterns include MVC, MVVM, Singleton, Factory, and Observer.

• MVC separates data, view, and controller logic

• MVVM adds a view model to handle data binding

• Singleton ensures only one instance of a class exists

• Factory creates objects without exposing the creation logic

• Observer allows objects to be notified of changes in other objects

ASP.NET Core is a cross-platform, high-performance framework for building modern, cloud-based, internet-connected applications.

• Cross-platform framework for building web applications

• High-performance and scalable

• Supports cloud-based and internet-connected applications

• Open-source and actively maintained by Microsoft

• Modular design for flexibility and extensibility

Use the DISTINCT keyword in an SQL query to remove duplicate records.

• Use the SELECT DISTINCT statement to retrieve unique records.

• Identify the columns that should be used to determine uniqueness.

• Consider using GROUP BY clause with aggregate functions if needed.

Optimizing SQL queries involves using indexes, minimizing data retrieval, and avoiding unnecessary joins.

• Use indexes on columns frequently used in WHERE clauses

• Minimize data retrieval by selecting only necessary columns

• Avoid unnecessary joins by using EXISTS or IN clauses instead of JOINs

Indexing in SQL is used to improve the performance of queries by creating a data structure that allows for faster retrieval of data.

• Types of indexing include clustered and non-clustered indexes

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

• Non-clustered indexes create a separate data structure that includes the indexed columns and a pointer to the actual data

• Indexes can be created on single or multiple columns to improve query performance

States are mutable data managed within a component, while Props are immutable data passed from parent to child components.

• States are managed within a component and can be changed by the component itself

• Props are passed from parent to child components and cannot be changed by the child component

• States are used for internal component data management, while Props are used for passing data from parent to child components

Yes, we can keep the reference variable of a parent class in the object of a child class.

• This is possible because a child class is a type of parent class and can inherit its properties and methods.

• This allows for polymorphism, where a parent class reference variable can refer to an object of a child class.

• For example, if we have a parent class Animal and a child class Dog, we can create an object of Dog and assign it to an Animal reference variable.

Entity Framework Core is an ORM framework that allows developers to work with databases using .NET applications.

• Entity Framework Core is an Object-Relational Mapping (ORM) framework for .NET applications.

• It allows developers to work with databases using .NET objects and LINQ queries.

• EF Core supports various database providers such as SQL Server, SQLite, MySQL, etc.

• It simplifies data access and persistence by handling database operations through code rather than SQL queries.

LINQ (Language Integrated Query) is a feature in C# that allows for querying data from different data sources using a uniform syntax.

• LINQ allows for querying data from collections, databases, XML, and more.

• It provides a set of standard query operators like Where, Select, OrderBy, etc.

• LINQ queries are written in a declarative syntax similar to SQL.

• Example: var result = from num in numbers where num % 2 == 0 select num;

Clustered index physically reorders the data in the table while non-clustered index creates a separate structure.

• Clustered index determines the physical order of data in the table, while non-clustered index does not.

• A table can have only one clustered index but multiple non-clustered indexes.

• Clustered index is faster for retrieval of data but slower for insert and update operations.

• Non-clustered index is slower for retrieval but faster for insert and update operations.

• Example...read more

Java doesn't support multiple inheritance to avoid the diamond problem.

• Java supports multiple interface inheritance.

• Diamond problem occurs when two superclasses have a common method.

• Java uses interfaces to achieve multiple inheritance.

• C++ supports multiple inheritance but requires virtual inheritance to avoid the diamond problem.

Objects get memory in Java from the heap memory.

• Java uses heap memory to allocate memory to objects.

• The heap memory is managed by the JVM.

• Objects are created using the 'new' keyword.

• The memory allocated to an object is released by the garbage collector when it is no longer in use.

OOPS principles are the basic concepts of Object-Oriented Programming that help in designing and implementing software solutions.

• Abstraction - hiding implementation details

• Encapsulation - binding data and functions together

• Inheritance - reusing code and creating new classes from existing ones

• Polymorphism - using a single interface to represent multiple types

• Composition - combining objects to create more complex ones

Exceptions in Java are handled using try-catch blocks.

• Exceptions are thrown when an error occurs during runtime.

• The try block contains the code that may throw an exception.

• The catch block catches the exception and handles it.

• Multiple catch blocks can be used to handle different types of exceptions.

• The finally block is executed regardless of whether an exception is thrown or not.

Typecasting is the process of converting one data type to another data type in programming.

• Typecasting is also known as type conversion.

• There are two types of typecasting: implicit and explicit.

• Implicit typecasting is done automatically by the compiler.

• Explicit typecasting is done manually by the programmer.

• Examples of typecasting include converting an integer to a float or a string to an integer.

Java program compiles into bytecode which is executed by JVM.

• Java code is written in .java files

• Compiler converts .java files into .class files containing bytecode

• JVM executes the bytecode

• JVM provides platform independence

• Java programs can be run on any platform with JVM installed

A reference variable in Java is a variable that holds the memory address of an object.

• Reference variables are used to access the methods and properties of an object.

• They are declared using the class name followed by the variable name.

• They can be assigned null or an object of the declared class or its subclasses.

• They are passed by value, but the value is the memory address of the object.

• Example: String str = new String("Hello World");

• Example: Object obj = null;

Upcasting is converting a derived class object to its base class type. Downcasting is the opposite.

• Upcasting is safe and implicit

• Downcasting is explicit and may cause runtime errors

• Upcasting can be used for polymorphism

• Downcasting is used to access derived class specific members

• Example: Animal a = new Dog(); // upcasting

• Example: Dog d = (Dog) a; // downcasting