50 Interview Questionnaire C# for experienced

 

C# & OOPS

1.      What is serialization? Object to binary stream.

2.      What is boxing and unboxing?- value to reference viceversa

3.      What are different types available in c#? value , reference

4.      Is it possible to serialize any HashMap? No in c#, yes in java, in c# HashTable

5.      What is CLR? Any dot.net language->CIL->CLR->Machine code

6.       How to create custom delegates? Use of it.

A custom delegate is a delegate that is created by the user. To create a custom delegate, you need to declare a custom delegate with the format which is exactly equal to the method, create the object of custom delegate, and invoke the method. improve readability, run time method selection, asynchronous execution and multicasting

7.      What is mean by low data type and high data type? Low/primitive high/non-primitive variables

8.      What is constant? Have you used it? PI, whose value set at compile, never change at run time.

9.      Difference between var and dynamic in c#? var knows the data type at compile time, dynamic at run time.

10.  What is object pool? Container that holds objects, also known as object caching.

11.  What is delegate, event handlers, Multicast Delegate? With example?pointer to function used for call back., multicast used for multiple call back. Event encapsulates delegate and implement publisher and subscriber model.

12.  Various classes that we have it in c#? Static class, Abstract class, Partial class, Sealed class

13.  What are partial class importance? extend functionality, multiple developers can work separately,

14.  What is sealed class? Can not be inherited.

15.  What is encapsulation and how to implement in code? Class hides private members and show public members.

16.  Difference between string and string builder? method shadowing / method hiding? Mutable means the string which can be changed. So String objects are immutable but StringBuilder is the mutable string type, method shadowing / method hiding: if both parent and child have same method name, the child class hides the parent.

17.  Difference between abstract class/interface?

18.  What is data abstraction? Hide

19.  Default behavior for the abstract class? Can not be instantiated, must be inherited,

20.  Usage of POCO classes? Plain old CLR object, which doesn't depend on any framework-specific base class.

21.  Abstract class and live project example?

·        An abstract class cannot be instantiated.

·        An abstract class may contain abstract methods and accessors.

·        Modifying an abstract class with the sealed modifier is impossible because the two modifiers have opposite meanings. The sealed modifier prevents a class from being inherited, and the abstract modifier requires a class to be inherited.

·        A non-abstract class derived from an abstract class must include actual implementations of all inherited abstract methods and accessors(get/set).

What are different types of classes in C#? (c-sharpcorner.com)

 

22.  Can we create static method in Abstract class? YES

23.  How to implement Interface class to dealing with multiple databases? using Repository/UnitOfWork patterns

24.  I have interface, I want to make protected interface is that possible? Nop,

25.  I have interface with 10 methods, I must inherit only certain method in derived class. Break the interface into smaller interfaces and inherit the interface you need.

26.  Can implement static method in abstract class? yes

27.  Can we override method in derived class and how? Always. Using virtual override 

28.  What do you mean encapsulation?

29.  what is the use of indexer? Indexer is a highly specialized property which allows instances of a class (or struct) to be indexed just like an array (properties can be static but indexers cannot).

30.  what is overloading, overriding?

31.  what is yield keyword? It helps to provide custom iteration without creating temp collections.

It helps to do stateful iteration.

32.  can you create instance for the abstract class?Nop

33.  what is the use static class? Simpler organized faster ex: math

34.  diff types of variables? Example: int Variable_Name=0;

35.  constant and read-only variable?

36.  diff var and dynamic?

37.  what extension methods?

38.  diff inheritance and extension?

39.  what is abstract class?

40.  what are oops concepts?

41.  What is reflection in C#

42.  Explain Generics & collections?

43.  What is dictionary type?

44.  Diff between hash table & dictionary?

45.  custom event handlers? Delegate custom event using subscriber client method

46.  What is Dependency Injection and types?3 types, Constructors, setters, interface setters

47.  Method hiding?

48.  Structure and class similarities?

49.  Is it possible to convert list to serialize?

 

 

 

Entity Framework

1.      Describe Entity Framework and how entity framework bridges connection between application and database?

2.      What is Entity Framework? Entity Framework Core is a great go-to ORM for .NET, for any type of application provides almost all the functionality required to do successful database access out the box.

3.      Disadvantage of EF?

·       Lazy loading is the main drawback of EF.

·       Its syntax is complicated.

·       Its logical schema is not able to understand business entities and relation among each other.

·       Logical schema of database is not capable of using certain parts of application.

·       It is not available for every RDMS.

 

4.      Explain Caching with example?

5.      Caching is there in EE, how you used caching in EE? Query caching

6.      Entity type data models.

7.      Which approach have you used? To synch data what are those files used using EF?

8.      Different loading mechanism we have it in EF?

9.      What is lazy loading is all about?

10.  What is DBContext used in EF?

11.  How do we use DB first approach in EF?

12.  What is edmx file contains?

13.  What is t4 for entity framework.

14.  What are the different types of data models?

·       Conceptual Data Model,

·       Representational Data Model

·       Physical Data Model

15.  I need to perform, delete record, and insert, rollback, how to achieve that?

16.  EF? highest salary write code in LINQ? (from emp in employees

                                                                       select salary).Max();

17.  Which type you used in EF, what is edmx?

18.  Nuget package is required for EF?

19.  Dataset, DbContext?

 

SOLID Principles

1.      What is solid principle is all about?

2.      What are those factors to be good design software code?

3.      Explain L part of solid with proper example?

4.      What is benefits when we use it solid principles?

5.      What is reduce complexity in solid principles?

6.      In what way solid principles will help?

7.      Explain Dependency Injection?

8.      Solid principle included in the example: farmer, child. how can we principle we can apply here, write code in hacker rank link?

9.      What is DI and types of DI and any tool which helps to implement?

10.  What is Multi tenancy?

11.  Solid principles importance?

DESIGN Patterns

1.      Is necessary to make singleton thread safe class?

2.      Give real time example for singleton class thread safe?

3.      Singleton is thread safe or not?

4.      Can you give example for factory design pattern?

5.      Have you worked on visitor pattern?

6.      What are design patterns?

7.      Explain Design pattern other than singleton pattern?

8.      Explain Singleton Design Pattern with project example?

9.      What is visitor pattern?

10.  Any commercial domain or take example, dependency injection is used?

11.  Can you discuss adapter design pattern?

12.  Write sample code step for the adapter design pattern using hacker rank link?

13.  Design pattern you aware of?

14.  Any idea about UnitOfWork? Repository pattern.

15.  What is use of UnitOfWork and its working?

16.  Situation: do we need to create multiple repository or one?

 

 

SQL SERVER

1.      What are DML command is all about?

2.      What is DLL command?

3.      What are message queues? have you used? And how used it?

4.      What are Joins in SQL Server?

5.      SQL? magic tables?

6.      Common table expression? SQL?

 

ASP.NET MVC

1.      Can you elaborate MVC architecture? Model view controller

2.      Explain MVC life cycle?

3.      How you handle validations in MVC?

4.      Authorization, Action, Result and exception filters?

5. ASP DOTNET MVC - ASP DOTNET Advanced
6. ASP DOTNET MVC - ASP DOTNET Basics
7. ASP DOTNET MVC - DOTNET Design
8. ASP DOTNET MVC - DOTNET Framework Basics
9. ASP DOTNET MVC - DOTNET Programming
10. ASP DOTNET MVC - Security
11. ASP NET MVC - Actions
12. ASP NET MVC - Caching and Filters
13. ASP NET MVC - Controller
14. ASP NET MVC - JavaScript and Ajax
15. ASP NET MVC - Model
16. ASP NET MVC - Overview
17. ASP NET MVC - Routing
18. ASP NET MVC - Validations
19. ASP NET MVC - Views
20. DOTNET Framework - Advanced
21. Web API
22. C#

23.   

LINQ

1.       Write LINQ query from a given scenario: highest salary from Employee table/Entity

Multi-Threading

1.      What is Threading?

Exception Handling & Troubleshooting

1.       Exception handling?

2.       How you handle exception?

3.       How Try, Catch & Finally blocks works?

Programming

1.       Design pattern? thread safe singleton pattern write code?

2.       Frequency of given character in the code example in hacker rank? and write piece of logic? display each char count in the given string ("this is an apple"). method to count character occurrences in C#:

3.       Write program for Split string and print url, username & pwd from string input=http://www.google.com:username@gmail.com:pwd

4.       what will be the output from the below code: code given from Hack rank link (some code snippet in C#)

5.       Write code for separate the char in the back at given text with & $%^& characters and Numbers 895623 in hr link.

 

 

 

 

 

 

React .js

1.      Explain props and state in React with differences

Props are used to pass data from one component to another. The state is local data storage that is local to the component only and cannot be passed to other components.

5. What is virtual DOM in React?

React uses Virtual DOM which is like a lightweight copy of the actual DOM(a virtual representation of the DOM). So for every object that exists in the original DOM, there is an object for that in React Virtual DOM. It is the same, but it does not have the power to directly change the layout of the document. Manipulating DOM is slow, but manipulating Virtual DOM is fast as nothing gets drawn on the screen. So each time there is a change in the state of our application, the virtual DOM gets updated first instead of the real DOM.

 

6. What is JSX?

JSX is basically a syntax extension of regular JavaScript and is used to create React elements. These elements are then rendered to the React DOM. All the React components are written in JSX. To embed any JavaScript expression in a piece of code written in JSX we will have to wrap that expression in curly braces {}.

 

Example of JSX: The name written in curly braces { } signifies JSX

 

 

const name = "Learner";

 

const element = (

  <h1>

    Hello,

    {name}.Welcome to GeeksforGeeks.

  </h1>

);

7. What are components and their type in React?

A Component is one of the core building blocks of React. In other words, we can say that every application you will develop in React will be made up of pieces called components. Components make the task of building UIs much easier.

 

 In React, we mainly have two types of components:

 

Functional Components: Functional components are simply javascript functions. We can create a functional component in React by writing a javascript function.

Class Components: The class components are a little more complex than the functional components. The functional components are not aware of the other components in your program whereas the class components can work with each other. We can pass data from one class component to another class component.

8. How do browsers read JSX?

In general, browsers are not capable of reading JSX and only can read pure JavaScript. The web browsers read JSX with the help of a transpiler. Transpilers are used to convert JSX into JavaScript. The transpiler used is called Babel

 

9. Explain the steps to create a react application and print Hello World?

To install React, first, make sure Node is installed on your computer. After installing Node. Open the terminal and type the following command.

 

npx create-react-app <<Application_Name>>

 

Navigate to the folder.

 

cd <<Application_Name>>

 

This is the first code of ReactJS Hello World!

 

 

import React from "react";

import "./App.css";

function App() {

  return <div className="App">Hello World !</div>;

}

export default App;

Type the following command to run the application

 

npm start

 

10. How to create an event in React?

To create an event write the following code.

 

 

function Component() {

  doSomething(e);

  {

    e.preventDefault();

    // Some more response to the event

  }

  return <button onEvent={doSomething}></button>;

}

11. Explain the creation of a List in react?

Lists are very useful when it comes to developing the UI of any website. Lists are mainly used for displaying menus on a website, for example, the navbar menu. To create a list in React use the map method of array as follows.

 

 

import React from "react";

import ReactDOM from "react-dom";

 

const numbers = [1, 2, 3, 4, 5];

 

const updatedNums = numbers.map((number) => {

  return <li>{number}</li>;

});

 

ReactDOM.render(<ul>{updatedNums}</ul>, document.getElementById("root"));

12. What is a key in React?

A “key” is a special string attribute you need to include when creating lists of elements in React. Keys are used in React to identify which items in the list are changed, updated, or deleted. In other words, we can say that keys are used to give an identity to the elements in the lists.

 

13. How to write a comment in React?

There are two ways to write comments in React.

 

Multi-line comment: We can write multi-line comments in React using the asterisk format /* */.

Single line comment: We can write single comments in React using the double forward slash //.

14. Explain the difference between React and Angular?

Field

React.js

Angular

Used as             

React.js is a JavaScript library. As it indicates react js updates only the virtual DOM is present and the data flow is always in a single direction.

 

Angular is a framework. Angular updates the Real DOM and the data flow is ensured in the architecture in both directions.

 

Architecture   

React.js is more simplified as it follows MVC ie., Model View Control.

 

The architecture is complex as it follows MVVM models ie., Model View-ViewModel.

 

Scalability         It is highly scalable.     It is less scalable than React JS.

Data Binding    It supports Uni-directional data binding which is one-way data binding.        It supports Bi-directional data binding which is two data binding.

DOM    It has a virtual DOM.   It has regular DOM.

15. Explain the use of render method in React?

React renders HTML to the web page by using a function called render(). The purpose of the function is to display the specified HTML code inside the specified HTML element. In the render() method, we can read props and state and return our JSX code to the root component of our app.

 

16. What is state in React?

The state is an instance of React Component Class that can be defined as an object of a set of observable properties that control the behaviour of the component. In other words, the State of a component is an object that holds some information that may change over the lifetime of the component.

 

17. Explain props in React?

React allows us to pass information to a Component using something called props (which stands for properties). Props are objects which can be used inside a component

 

We can access any props inside from the component’s class to which the props is passed. The props can be accessed as shown below:

 

this.props.propName;

 

18. What is higher-order component in React?

Higher-order components or HOC is the advanced method of reusing the component functionality logic. It simply takes the original component and returns the enhanced component. HOC are beneficial as they are easy to code and read. Also, helps to get rid of copying the same logic in every component.

 

19. Explain the difference between functional and class component in React?

Functional Components                                                 Class Components               

A functional component is just a plain JavaScript pure function that accepts props as an argument              A class component requires you to extend from React. Component and create a render function

No render method used           It must have the render() method returning JSX

Also known as Stateless components               Also known as Stateful components

React lifecycle methods (for example, componentDidMount) cannot be used in functional components.    React lifecycle methods can be used inside class components (for example, componentDidMount).

Constructors are not used.      Constructor is used as it needs to store state.

20. Explain one way data binding in React?

ReactJS uses one-way data binding which can be Component to View or View to Component. It is also known as one-way data flow, which means the data has one, and only one way to be transferred to other parts of the application. In essence, this means child components are not able to update the data that is coming from the parent component. It is easy to debug and less prone to errors.

 

React Intermediate Interview Questions

Here, we cover all intermediate level react interview questions with answers, that recommeded for freshers as well as for experienced professionals having 1 – 2 years of experience.

 

21. What is conditional rendering in React?

When there are multiple components in react and we want to render components according to our preference and some conditions then we use conditional rendering. In conditional rendering, a condition is specified and if the condition is passed then this component is rendered.

 

Let us look at this sample code to understand conditional rendering.

 

{isLoggedIn == false ? <DisplayLoggedOut /> : <DisplayLoggedIn />}

 

Here if the boolean isLoggedIn is false then the DisplayLoggedOut component will be rendered otherwise DisplayLoggedIn component will be rendered.

 

22. What is react router?

React Router is a standard library for routing in React. It enables the navigation among views of various components in a React Application, allows changing the browser URL, and keeps the UI in sync with the URL.

 

To install react router type the following command.

 

npm i react-router-dom

 

23. Explain the components of a react-router

The main components of a react-router are:

 

Router(usually imported as BrowserRouter):  It is the parent component that is used to store all of the other components. Everything within this will be part of the routing functionality

Switch: The switch component is used to render only the first route that matches the location rather than rendering all matching routes.

Route: This component checks the current URL and displays the component associated with that exact path. All routes are placed within the switch components.

Link: The Link component is used to create links to different routes.

24. Explain the lifecycle methods of components

A React Component can go through four stages of its life as follows.

 

Initialization: This is the stage where the component is constructed with the given Props and default state. This is done in the constructor of a Component Class.

Mounting: Mounting is the stage of rendering the JSX returned by the render method itself.

Updating: Updating is the stage when the state of a component is updated and the application is repainted.

Unmounting: As the name suggests Unmounting is the final step of the component lifecycle where the component is removed from the page.

25. Explain the methods used in mounting phase of components

Mounting is the phase of the component lifecycle when the initialization of the component is completed and the component is mounted on the DOM and rendered for the first time on the webpage. he mounting phase consists of two such predefined functions as described below

 

componentWillMount() Function: This function is invoked right before the component is mounted on the DOM.

componentDidMount() Function: This function is invoked right after the component is mounted on the DOM.

26. What is this.setState function in React?

We use the setState() method to change the state object. It ensures that the component has been updated and calls for re-rendering of the component. The state object of a component may contain multiple attributes and React allows using setState() function to update only a subset of those attributes as well as using multiple setState() methods to update each attribute value independently.

 

27.  What is the use of ref in React?

Refs are a function provided by React to access the DOM element and the React element that you might have created on your own. They are used in cases where we want to change the value of a child component, without making use of props and all. They have wide functionality as we can use callbacks with them.

 

The syntax to use ref is

 

const node = this.myCallRef.current;

 

28. What are hooks in React?

 Hooks are a new addition in React 16.8. They let developers use state and other React features without writing a class. Hooks doesn’t violate any existing React concepts. Instead, Hooks provide a direct API to react concepts such as props, state, context, refs and life-cycle

 

29. Explain the useState hook in React?

The most used hook in React is the useState() hook. It allows functional components to manipulate DOM elements before each render. Using this hook we can declare a state variable inside a function but only one state variable can be declared using a single useState() hook. Whenever the useState() hook is used, the value of the state variable is changed and the new variable is stored in a new cell in the stack.

 

We have to import this hook in React using the following syntax

 

import {useState} from 'react'

 

30. Explain the useEffect hook in react?

The useEffect hook in React eliminates the side effect of using class based components. It is used as an alternative to componentDidUpdate() method. The useEffect hook accepts two arguments where second argument is optional.

 

useEffect(function, dependency)

 

The dependency decides when the component will be updated again after rendering.

 

31. What is React Fragments?

when we are trying to render more than one root element we have to put the entire content inside the ‘div’ tag which is not loved by many developers. So since React 16.2 version, Fragments were introduced, and we use them instead of the extraneous ‘div’ tag. The following syntax is used to create fragment in react.

 

<React.Fragment> 

    <h2>Child-1</h2>  

    <p> Child-2</p>  

</React.Fragment> 

 

32. What is a react developer tool?

React Developer Tools is a Chrome DevTools extension for the React JavaScript library. A very useful tool, if you are working on React.js applications. This extension adds React debugging tools to the Chrome Developer Tools. It helps you to inspect and edit the React component tree that builds the page, and for each component, one can check the props, the state, hooks, etc.

 

33. How to use styles in ReactJS?

CSS modules are a way to locally scope the content of your CSS file. We can create a CSS module file by naming our CSS file as App.modules.css and then it can be imported inside App.js file using the special syntax mentioned below.

 

Syntax:

 

import styles from './App.module.css';

 

34. Explain styled components in React?

Styled-component Module allows us to write CSS within JavaScript in a very modular and reusable way in React. Instead of having one global CSS file for a React project, we can use styled-component for enhancing the developer experience. It also removes the mapping between components and styles – using components as a low-level styling construct

 

The command to install styled components is

 

npm i styled-components

 

Using the below code we can custom style a button in React

 

 

import styled from 'styled-components'

 

const Button = styled.div`

width : 100px ;

cursor: pointer ;

text-decoration : none;

`

 

export default Button;

35. What is prop drilling and its disadvantages?

Prop drilling is basically a situation when the same data is being sent at almost every level due to requirements in the final level. The problem with Prop Drilling is that whenever data from the Parent component will be needed, it would have to come from each level, Regardless of the fact that it is not needed there and simply needed in last.

 

For further reading, check out our dedicated article on Intermediate ReactJS Intermediate Interview Questions. Inside, you’ll discover over 20 questions with detailed answers.

 

React Interview Questions For Experienced

Here, we cover advanced react interview questions with answers for experienced professionals, who have over 5+ years of experience.

 

36. What is custom hooks in React?

Custom hooks are normal JavaScript functions whose names start with “use” and they may call other hooks. We use custom hooks to maintain the DRY concept that is Don’t Repeat Yourself. It helps us to write a logic once and use it anywhere in the code.

 

37. How to optimize a React code?

We can improve our react code by following these practices:

 

Using binding functions in constructors

Eliminating the use of inline attributes as they slow the process of loading

Avoiding extra tags by using React fragments

Lazy loading

38. What is the difference between useref and createRef in React ?

useRef

 

createRef

 

It is a hook.      It is a function.

It uses the same ref throughout.         It creates a new ref every time.

It saves its value between re-renders in a functional component.    It creates a new ref for every re-render.

It returns a mutable ref object.            It returns a read-only ref object.

The refs created using the useRef can persist for the entire component lifetime.   The refs created using the createRef can be referenced throughout the component.

It is used in functional components.  It is used in class components.

39. What is react-redux?

React-redux is a state management tool which makes it easier to pass these states from one component to another irrespective of their position in the component tree and hence prevents the complexity of the application. As the number of components in our application increases it becomes difficult to pass state as props to multiple components. To overcome this situation we use react-redux

 

40. What are benefits of using react-redux?

They are several benfits of using react-redux such as:

 

It provides centralized state management i.e. a single store for whole application

It optimizes performance as it prevents re-rendering of component

Makes the process of debugging easier

Since it offers persistent state management therfore storing data for long times become easier

41. Explain the core components of react-redux?

There are four fundamental concepts of redux in react which decide how the data will flow through components

 

Redux Store: It is an object that holds the application state

Acrtion Creators: These are unctions that return actions (objects)

Actions: Actions are simple objects which conventionally have two properties- type and payload

Reducers: Reducers are pure functions that update the state of the application in response to actions

42. How can we combine multiple reducers in React?

When working with Redux we sometimes require multiple reducers. In many cases, multiple actions are needed, resulting in the requirement of multiple reducers. However, this can become problematic when creating the Redux store. To manage the multiple reducers we have function called combineReducers in the redux. This basically helps to combine multiple reducers into a single unit and use them.

 

Syntax:

 

import { combineReducers } from "redux";

const rootReducer = combineReducers({

    books: BooksReducer,

    activeBook: ActiveBook

});

 

43. What is context API?

Context API is used to pass global variables anywhere in the code. It helps when there is a need for sharing state between a lot of nested components. It is light in weight and easier to use, to create a context just need to call React.createContext(). It eliminates the need to install other dependencies or third-party libraries like redux for state management. It has two properties Provider and Consumer.

 

44. Explain provider and consumer in ContextAPI?

A provider is used to provide context to the whole application whereas a consumer consume the context provided by nearest provider. In other words The Provider acts as a parent it passes the state to its children whereas the Consumer uses the state that has been passed.

 

45. Explain CORS in React?

In ReactJS, Cross-Origin Resource Sharing (CORS) refers to the method that allows you to make requests to the server deployed at a different domain. As a reference, if the frontend and backend are at two different domains, we need CORS there.

 

We can setup CORS evironment in frontend using two methods:

 

axios

fetch

46. What is axios and how to use it in React?

Axios, which is a popular library is mainly used to send asynchronous HTTP requests to REST endpoints. This library is very useful to perform CRUD operations.

 

This popular library is used to communicate with the backend. Axios supports the Promise API, native to JS ES6.

Using Axios we make API requests in our application. Once the request is made we get the data in Return, and then we use this data in our project.

To install aixos package in react use the following command.

 

npm i axios

 

47. Write a program to create a counter with increment and decrement?

 

import React, { useState } from "react";

 

const App = () => {

 

// Counter is a state initialized to 0

const [counter, setCounter] = useState(0)

 

// Function is called everytime increment

// button is clicked

const handleClick1 = () => {

 

// Counter state is incremented

setCounter(counter + 1)

}

 

// Function is called everytime decrement

// button is clicked

const handleClick2 = () => {

 

// Counter state is decremented

setCounter(counter - 1)

}

 

return (

<div>

    <div>

        {counter}

    </div>

    <div className="buttons">

        <button onClick={handleClick1}>

            Increment

        </button>

        <button onClick={handleClick2}>

            Decrement

        </button>

    </div>

</div>

)

}

 

export default App

48. Explain why and how to update state of components using callback?

It is advised to use a callback-based approach to update the state using setState because it solves lots of bugs upfront that may occur in the future.We can use the following syntax to update state using callback

 

this.setState(st => {

    return(

        st.stateName1 = state1UpdatedValue,

        st.stateName2 = state2UpdatedValue

    )

})

 

49. What is React-Material UI?

React Material UI is a framework built upon React library which contains predefined components to create React applications. Material UI is a design language built by Google in 2014 and works with various JavaScript frameworks apart from React such as Angular.js and Vue.js. The quality of the inbuilt designs of Material UI and its easy implementation makes it the first choice of most developers. The inbuilt components are also customizable so it helps easily recreate the designs.

 

50. What is flux architecture in redux?

Flux is AN architecture that Facebook uses internally when operating with React. It is merely a replacement quite an architecture that enhances React and also the idea of unidirectional data flow.