Top C# Interview Questions And Answers | C# Interview Preparation | C# Training | Simplilearn

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sharp interview questions and answers

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this tutorial video has 50 interview

questions and all these questions are

divided into three levels beginner

intermediate and advanced levels so

without further ado let's get started

with the first topic

now before getting into any interview

questions i would like to reveal the

first type of questions that are

recording interview questions it is

obvious that in any technical interview

you will be asked to code some or the

other program so we have bought the most

frequently asked top five coding based

questions in c sharp which are write a

program in c sharp to reverse a string

write a program in c sharp to find if a

given string is a palindrome or not

write a c sharp program to find the

substring from a given string write a c

sharp program to find if a positive

integer is prime or not and lastly write

a singleton design pattern and how to

implement them in c sharp

so these are the most frequently asked

coding based interview questions based

on c sharp and if you want we would like

to share these quotes with you please

feel free to share us your email ids in

the comments section below so that we

can share you all these codes

now let's start with the beginner level

interview questions

so our first question is how the c

programming language differs from

c-sharp programming language the first

difference is that the c programming

language allows for procedural

programming whereas c-sharp programming

language provides object-oriented

programming the second difference is

that c programming language supports

pointers whereas in c sharp pointers are

only used in unsafe mode the third

difference between c and c sharp is that

garbage collection is not supported in c

whereas in c sharp garbage collection is

handled by the common language runtime

or clr

the next difference between the both is

the c programming language is cross

platform in contrast the dot net

framework is required to run on the

c-sharp language only fifth difference

between c and c sharp is we can achieve

a low level of abstraction using c

programming language whereas in c sharp

we can achieve a high level abstraction

the last difference between the both is

the c programming language is primarily

used in commercial industries and

engineering whereas c sharp on the other

hand is used for software development

and other network related goals

the second question is what is an object

and a class in c c-sharp

the answer for this question is a class

is a collection of properties and

methods used to represent a real-time

entity it is data structure that groups

all the instances into a single unit

whereas an object of a class is defined

as an instance technically it is simply

a block of memory that can be stored as

variables arrays or collections for

example the car is working as a class on

my screen and the objects are ford and

rd which are the car manufacturers

next is what are the fundamentals of

object-oriented programming

the answer for this question is the

object-oriented programming language or

oops in c-sharp is divided into four

concepts that is encapsulation

abstraction

inheritance and polymorphism

let's take a closer look at each of the

four object oriented programming

concepts first encapsulation

encapsulation is defined as when an

object's internal representation is

hidden from the view outside its

definition it is said to be encapsulated

only the necessary information is

accessible while the rest of the data

implementation is hidden

next abstraction abstraction is the

process of identifying and eliminating

irrelevant details from the object's

critical behavior and data

following the oops concept inheritance

is the ability to create new classes

from existing ones it is accomplished by

gaining access to altering and extending

the behavior of objects in the parent

class

lastly we have polymorphism polymorphism

is defined as a name that means one name

many forms it is accomplished using

several methods with the same name but

different implementations

now we have the next question that is

what is the common language runtime or

clr so the answer for this question is

the common language runtime manages the

execution of dotnet programs clr the

just-in-time compiler translates

compiled code into machine instructions

this is the program that the computer

runs clr provides memory management

exception handling type safety and other

services now let's look at the next

question

what is managed and unmanaged code

so manage code is executed by clr common

language runtime on which all

application code is based the internet

platform because of this is regarded as

managed internally the dotnet framework

uses the garbage collector to clear

unused memory whereas unmanaged code is

any code executed by an application

runtime in a framework other than dotnet

the application runtime will handle

memory security and other performance

operations

next we have

what exactly is an interface

in c sharp an interface is a class

blueprint it is like an abstract class

and that all the methods declared within

the interface are abstract

it cannot have a method in body and

cannot be instantiated instead it can be

used to achieve multiple inheritances

that can't reach

the following example demonstrates an

odd even class has access to both the

even and odd classes

now we have the next question

what are the different types of classes

in c sharp so the answer for this

question is there are four different

types of classes in c sharp the first is

partial class which states that its

members can be divided or shared across

multiple files the keyword partial

denotes it

the second class is abstract an abstract

class is one was object cannot be

instantiated the only way to get the

class is to inherit it must include at

least one method the keyword abstract

denotes the abstract classes the next

class is sealed class a sealed class

cannot be inherited to access a sealed

class members we must create a classes

object then the keyword seal denotes it

the last and the fourth class in c sharp

is static this class does not allow

inheritance the classes members are also

static the keyword static denotes this

type of class the keyword instructs the

compiler to look for any static class

instances created by accident

now the ninth question

what is the difference between equality

operator and equals method in c sharp

the difference between the equality

operator which is double equals to and

equals method in c sharp is the the

double equals operator and the equals

method compare two values or reference

type data items

this answer explains the fundamental

distinction between two the comparison

operator is the equality operator and

the equals method compares the contents

of the string the double equals to

operator compares the identity of

reference whereas the equals method

compares the only reference

now we have the tenth question

explain code compilation in c sharp

the answer for this question is in c

sharp code compilation consists of three

steps the c-sharp compiler compiles the

source code into managed code putting

the newly created code together into

assemblies

then the common language runtime is

being loaded and clr is carrying out the

assembly

now we have the 11th question what are

the differences between a class and

struct

the answer for this question is

the first difference is class can

inherit whereas struct cannot the second

difference is a class is passed by

reference type whereas struct is passed

by value type

the next difference is class members are

private by default whereas in struct

members are public by default

the fourth difference is class is

appropriate for large complex operations

and objects though struct is appropriate

for small isolated models the last

difference between the boat is we can

use a garbage collector to manage memory

in class whereas a struct cannot use

garbage collector and thus cannot manage

memory

the next question is what is the

difference between virtual method and

abstract method

virtual method is default implementation

of virtual process is always required it

can however be overridden in the derived

class though this is not required for

example the override keyword can be used

to override it

though an abstract method has no

implementation it belongs to the

abstract class therefore derived class

must implement the abstract form

although an override keyword is not

required in this case it can be used

now the 13th question explain namespaces

in c sharp

namespaces are employed in organization

of large code projects for example in c

sharp the most common namespace is

system we can create our namespaces and

use one namespace with another known as

nested namespaces the keyword namespace

is used to identify them

following the c-sharp interview

questions and answers the next question

is what is the using statement the

answer for this question is the using

keyword indicates the program uses the

specified namespace as an example

consider system the system is a

namespace in this context

the class console is defined in the

system module so in our program we can

use a console write line and read line

now the next question is explain

abstraction

one of the object oriented concepts is

abstraction it is used to display only

the classes essential features and hide

unnecessary information

let us use a car for an example

a car driver should be familiar with the

vehicle's details such as color name

mirror steering gear brake and so on he

doesn't need to know about the internal

combustion engine and an exhaust system

as a result abstraction aids in knowing

what is required and concealing internal

details from the outside internal

information can be hidden by declaring

such as parameters as private and using

the private keyword

the following question is explain

polymorphism polymorphism in programming

means the same method but different

implementations it is classified into

two types compile time polymorphism and

runtime polymorphism the compile-time

polymorphism results the call in

compile-time polymorphism is also

referred to as static binding early

binding and overloading

the compiler does not resolve the

runtime polymorphism call and is also

referred to as dynamic binding late

binding or overriding

for example a man acts as a father a

husband and an employee all

simultaneously the next question

how is exception handling implemented in

c sharp in c sharp exception handling is

accomplished using four keywords try

catch finally and through

in try try contains a block of code that

will be checked for exceptions in catch

a program that catches an exception with

the help of the exception handler and

finally it is a block of code written to

run regardless of whether an exception

is scored or not and finally through

throw is when a problem occurs it throws

an exception

followed by exception handling we have

another question

that is what are the c sharp input and

output classes what are commonly used

for input and output classes

the system.io namespace in c sharp

contains classes used to perform various

operations on files such as creating

deleting opening closing etc

the following are some of the examples

of commonly used input output classes

which are file stream writer stream

reader string writer string reader part

etc

file aids to with the manipulation of a

file

stream writer is the class that is used

to write characters to a string

the stream reader is used to read

characters from stream the string writer

is used to write a string buffer the

string reader is used to read the string

buffer the path is used to perform

operations on path information followed

by that the next question is what is

stream reader or stream writer class the

answer for this question is

the name space system dot input output

contains the classes stream radar stream

writer which are used to read and write

character 90 database data

members of stream reader are close read

and read line members of stream writer

are close right and right line

there is an example on my screen where

you have code block to read and

a code block to write using stream

reader and stream writer now the next

question what is a destructor in

seashore destructor are used to clear

memory and free resources in c sharp

however this is handled by a garbage

collector on its own internally system

dot gc dot collect is used to clean up

but it may be necessary to implement

destructors in some classes manually

the following is an example of vehicle

acting as a destructor using the tide

symbol following the 20th question we

have the 21st question which says what

is an abstract class

so the answer for this question is an

abstract class is denoted by the

abstract keyword and only be used as a

base class this class should always be

inherited it is impossible to create an

instance of the class itself if we don't

want any program to create an object of

a class we can make it as categories

abstract there are no implementations of

any methods in the abstract class they

must be implemented in the child class

here's an example that shows an abstract

as abs then the child as child class

that inherits the abs abstract class and

finally an object as c is one of the

accesses

the addition function via a new process

called submission

and abstract classes methods are all

implicitly virtual as a result the

virtual keyword should not be used with

any abstract classes methods they must

however be implemented in the child

class the next question is what is the

difference between boxing and unboxing

codes

boxing is converting a value type to a

reference type at the same time unboxing

is the explicit conversion of the same

reference type back to the value type

the following is an example val 1 is 50

which is going through boxing process

and val 1 is converted into object

boxing val which is then converted back

into an unboxing variable after the

boxing process

the following question is what is the

difference between continue and break

statement the break statement terminates

the loop it causes the program control

to exit the loop in contrast the

continue statement instructs the

program's power to go only to the

current iteration however it does not

affect the loop

following is an example for break

statement in which the break keyword is

used to terminate the loop going from 0

to 10 immediately the continue block of

code is used to skip the current

iteration of 2. the final question for

the beginner level is what is difference

between final finally and finalized

blocks

final is a keyword that indicates that a

variable method or a class is

unchangeable to put it simply finally

like try and catch blocks it is used for

exception handling the final block is

always executed regardless of whether an

exception is raised

this block is mainly used to close

database connections input output

resources etc lastly the finalized

method in java.lang protected method

object type it is passed down to every

java class you create therefore the

garbage collector thread calls this

method before removing an object from

memory now we have reached the

intermediate level

the 25th question on our list is what

exactly is an array so the answer for

this question is an array is a data

structure that stores multiple variables

of the same data type it is a set of

variables stored in a single memory

location here's an example of marks

array with 5 integer values 10 20 30 40

and 50. a single dimensional array is a

linear array that stores variables in a

single row the preceding example is a

one-dimensional array arrays can have

multiple dimensions rectangular arrays

are another name for multi-dimensional

arrays we have a multi-dimensional array

as numbers with three rows and three

columns with one two and three in the

first row three four and five in the

second row and four five and six in the

third row

now the next question is what is a jack

arry

a jagged array is an array with array

elements it is also known as an array of

arrays and can have a single dimension

or multiple dimensions here's an example

of jack arry a jagged array with four

rows

in the first row we have two values one

and two the next row contains values

three four and five and six the third

row includes three values seven eight

and nine and the fourth row contains

five values that is three four five six

and seven

now the next question name some

properties of arrays

an array has following properties that

is length this function returns the

total number of elements in an irene

size

this indicates whether the array's

length is fixed or not

read-only this indicates whether the

array is read-only or not

now we have 28th question

what is an array class

arrays can be created manipulated

searched for and sorted using array

class however the array class does not

belong to the system however the

collection's namespace is still

considered because it implements the

list interface therefore the ira class

serves as the foundation for area

supporting language implementations

we have an array class called colors and

we have four colors red blue green and

yellow we print those colors in this

array class example

now the next question is what exactly is

a string what are the characters of

string class a string is the grouped

character objects string variables that

can be declared in c sharp a string

class in c sharp represents a string in

the following example we have a string

called name that is inserted by c sharp

interview questions and answers the

string class has the following

properties

character returns the current strings

character object the length function

returns the number of objects in this

current string

another 30th question

what is an escape sequence named some

strings escape sequences in c sharp in c

sharp a backslash indicates the escape

sequence the backslash indicates that

the character should be interpreted

literally or unique

an escape sequence is treated as if

there were a single character first we

have backslash n which means newline

character next we have backslash b which

is used for backspace then we have two

types of backslash which represents

backslash itself after that we have a

single backslash code and lastly we have

backslash double quote now the 31st

question

what are regular expressions search a

string using regular expressions

a regular expression is a template that

can match a set of input operators

constructs and character laterals can

all be used in the pattern for example

regex is used for string passing and

character string replacement an example

occurs 0 or more times before the

preceding character as a result

a star b predicts is equivalent to b

comma a b comma a a b comma a aap and so

on

following is the code language program

in which we have strings as c c plus

plus and c sharp then we have c l as an

object and try to find the string c

sharp as we can see c sharp is present

in the following string so we will print

as a match as found now the next

question what are the fundamental string

operations explain the following are

some examples of basic string operations

the first operation is concatenate a

system can concatenate two strings

string concatenate or use the plus

operator the next string operation is we

have modify replace x comma y is the

function that replaces one string with

another the trim function is used to cut

a string at the end or beginning third

string operation is compare operation

system dot string comparison is used to

compare two strings either case

sensitively or not at all it requires

two parameters the original string and

the string to be compared with the last

operation is a search operation used to

find specific string using the start

with and ends with methods

following question is what exactly is

passing how do you pass a date and time

string the answer with this question is

parsing is a process of converting a

string into another data type for

example consider the string value 100

which we are attempting to convert into

a number variable of integer data type

using pass function

as a result the pass method

converts string 100 into its base type

that is integer

following the same method to convert

date time string string date time is

equals to date july 24 2011.

datetime past while is equals to date

time and past method

date time

we will now move into the advanced level

interview questions

now the first one in advanced level

interview question is what is a delegate

explain

a delicate is a variable that holds the

reference to a method hence it is a

function pointer or reference type all

delegates are derived from

system.delegate namespace both delegate

and the technique that it refers can

have the same signature

declaring a delegate public delegate

void some numbers and number following a

delegate's declaration the

representative must create the object

using new keyword

some numbers sn1 is equals to some new

numbers of number the delegate acts as

an encapsulation for the reference

method which is called internally when a

delegate is called now the next question

how to use delegates with events

delegated authority is used to initiate

and manage events a delegate must always

particular at first following by the

events

this diagram gives three functions to

delete and the delegate to generate an

event that is an event generator

the next question is what are events

events are user actions that cause the

application to receive notifications to

which it must respond user actions can

include mouse movements keypress and so

on

a class that raises an event is known as

the publisher and the class that

responds or receives the event is known

as a subscriber

if an event does not have one subscriber

it is never raised events are declared

using delegates

in this example we have delegates as

print and os and event names as my event

1.

now the next question is what are the

different types of delegates and there

are three types of delegates the first

one is single delegate a single delegate

is a delegate that can only call one

method

the second type of delegate is the

multicast delegate a delegate that can

call multiple methods is known as a

multicast delegate the plus and minus

operators are used to subscribe and

unsubscribe the third type of delegate

is the generic delegate it does not

require a definition of an instance and

it is classified into three types that

is action function and

predicate

so the action is in the preceding

example of delegates the events we can

use the action keyword to replace the

definitions of delegate and even

function a function delegate defines a

method that can take arguments and

results and lastly we have predicate a

method that can be called with arguments

and always returns a bool

now followed by that we have the 38th

question

what do multicast delegates mean

the answer for this question is in c

sharp multicast delicate is a delegate

that holds the references to a multiple

functions when we invoke the multicast

delegate we gather all the tasks that

the delegate prefers for example if you

want to use a delegate to call multiple

methods all the method signatures must

be seen let's see a code example to

multicast delegate

this program uses a namespace delegate

and then declares delegate as a

multi-delegate with formal arguments a

and b

we define the addition and subtraction

functions in the class program which we

declare and calculate as class b and a

minus b respectively then in the main

function we create a class program

object p1 then we declare md1 and md2

objects for addition and subtraction

operations

then we assign md1 to md1 and md2 giving

a value of 100 to a and a value of 200

to b

now let's try to execute the program and

see the output

now the next question is what are

synchronous and asynchronous operations

so the answer for this question is

synchronization is a technique for

writing thread safe code in which only

one thread can access a resource at any

given time before continuing with the

program flow the asynchronous call waits

for the method to complete in

asynchronous mode the method calls

return immediately so that the program

can perform other operations while the

called method completes its work the

async and await keywords are used to

achieve asynchronous programming in c

sharp

our next question is what exactly is

reflection in c sharp reflection is the

ability of a code to access the

assemblies metadata during runtime a

program reflects itself and uses

metadata to inform or change its

behavior

system of namespace reflection includes

methods and classes for managing the

information of all loaded types and

techniques it is primarily used in

windows applications such as viewing the

properties of a button in a windows form

the class reflection members inform

object is used to discover the

attributes associated with the class

following that we have reached the next

question that is the 41st question what

is the generic class

generics is also known as gender classes

create courses or objects with no

specific data type for example the data

type can be assigned in runtime that is

the program uses it

let's see a simple code for generic

class

in this program we have name space as

generic class public class test class

and g to represent the generic class

after that we define an array namely

object 1 of generic type with length 5

then we have int variable as count 1

then we have a function as some adding

items mechanism into a generic type next

we have to keep adding items to an array

until the count plus one is less than

six then we have to keep increasing the

count value by one following that we

have an index variable for each

statement iteration in which we have to

get and set properties the get property

is used to return the index value and

the set property is used to set a value

with the same name as the index value

finally we instantiate a generic with an

integer with the object name int obj in

the main method then we add integer

values to the array and finally we

multiply all the values in the array

now let's try to execute this code and

see the output

now the program got successfully

executed and you can see the output

right on my screen

now the next question explain get and

set access properties

get and set are referred to accesses

properties make to use these the

property implements a mechanism for

reading and writing the value of a

private field these accesses are used to

gain access to a private field the get

property method is used to retrieve the

value of a property to change the value

use set property accessor and let's see

an example to understand this in a much

better way

we have a class name as a person name in

this program followed by two variants

firstly we have a private variable as n

for the person's name then we have

public variable

as name one we have get property that

returns variable n and finally we have a

set property that assigns variable m to

the variable value next the value

keyword denotes the value that we

transfer to the property n next in the

main function we have an object name as

my name where we give the name as abc

and finally we display the person's name

as abc

now the output is on my screen right

over here

now let's get back to the ppt

the next question is what exactly is a

thread

and what is multi-threading a thread is

a collection of instructions that can be

executed to allow our program to perform

concurrent processing confident

processing will enable us to perform

multiple operations at the same time

c-sharp has a thread by default however

the other threads can be created to run

code in parallel with the original code

this is accomplished by having different

threads handle different process

referred to as multi-threading to handle

multi-threaded operations several thread

methods are used start sleep about

suspend resume and join are all options

the next question is name some

properties of thread class

some of the properties of thread class

are first we have is alive property

it has work then when a thread is active

this value is actual

the following property is name which

returns the thread's name also can set

name for the thread following that we

have the next property as priority which

returns the prioritized value of this

task set by the operating system the

background is the following property of

thread class it gets or sets the value

that indicates whether a thread should

be a background process or a foreground

process last property is we have thread

state which describes the thread state

on the next question we have what are

the different states of a thread so the

different states of thread are

unstarted state which means a thread has

been created next we have running state

which means that the threat begins

execution weight sleep joint is the

third stage

in which a threat called sleep another

thread calls weight and another thread

calls join next we have suspense state

the thread has been halted about it is

the next state which the thread has died

but not being changed to the state

stopped

last is we have stop state which means

that this thread has come to a halt

followed by this we have the next

question which is what is a deadlock

a deadlock occurs when a process cannot

complete its execution because two or

more methods are awaiting the completion

of another

this is common in multi-threading

followed by that we have another

question explain lock monitors and mutex

object in multi-threading

a lock keyword ensures that only one

thread can enter a specific code section

at a time the preceding example lock ob

jx indicates that a lock placed on obx

until this process releases it at which

no point no other thread will be able to

access obj mutex is like lock but it can

work across multiple processes

simultaneously for example weight one

method is used to lock the lock and

release mutex is used to unlock it on

the other hand mutex is slower than lock

because it takes time to acquire and

release it monitor enter and observe

internally exits implements a lock a

lock is monitor shortcut internally and

lock objects is called you can see an

example right on my screen

the next question on the list is what is

race condition

a race condition occurs when two threads

access the same resource and attempt to

change it simultaneously it is

impossible to predict which thread will

be the first to access the resource if

we have two threads t1 and t2 both

attempt to access a shared resource

called x if both threads try to access

or write a value to x the last value

returned to x is saved

49th question in the list is what is

serialization and dc realization the

answer for this question is converting

code to binary format is known as

serialization once converted to budget

is simple to store and write to a disk

or other storage devices serialization

is most valuable when we don't want to

lose the original form of the code and

want to retrieve it at any time in the

future

dc realization refers to recovering

c-sharp code from binary form now the

50th question

what are the different types of

serialization now there are various

types of serialization which are as

follows

the first type of serialization is the

xml serialization the second one is soap

and the last and the third one is the

binary serialization

another 51st question what is an xsd

file

so an xsd file is an abbreviation for

xml schema definition it defines the

structure of an xml file it determines

which element should be represented in

the form of xml and in what order and

which property should be current

during serialization of c sharp code and

x sd.exe converts the classes into xsd

compiler form

now as discussed initially we will go

through some coding based interview

questions the document of code will be

sent to you feel free to write your

emails in the comment section below so

that we can respond to you at the

earliest

now program one is string reverse

so you can see that it is converting

simply learn into the reverse string

which is here

now let us go through the second program

real quick

now on my screen you can see the second

program the second program is based on

converting or checking if the string is

palindrome or not let's quickly execute

this

you can see that it is asking for enter

string

let us enter

p op pop

and it is saying as the string is apalan

rom now let us quickly execute the third

now the third one is based on substring

operations let's quickly execute the

code let's enter a string here simply

learn

so here you can see the substrings that

can be created using simply learn

now let's execute the fourth code so

this program is based on if checking the

number is prime or not

so now let's enter a number let's enter

7 which is a prime number which says

number is prime now the fifth question

is based on single ton

now let's try to execute this code and

see the output

now you can see the code got

successfully executed and the output is

over here hello and hi

now don't you worry about the code

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now with that we have come to an end of

this session on

c-sharp interview questions if you have

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