Top interview questions | Practice Quiz, MCQ Questions | Solutions for interview

Question 1

Which of the following is true about C#?

1

C# is a statically-typed language

2

C# supports multiple inheritance directly

3

C# does not support garbage collection

4

C# does not support object-oriented programming

5

None of the above

Question 2

What is the default access modifier for a class in C#?

1

Internal

2

Private

3

public

4

Protected

Question 3

Which of the following is NOT a valid C# data type?

1

double

2

int

3

real

4

float

Question 4

What is the output of the following C# code?

int a = 5, b = 2;
double result = a / b;
Console.WriteLine(result);

1

2.0

2

2.5

3

2

4

Compilation error

Question 5

Which of the following statements about C# constructors is true?

1

A class can have only one constructor

2

A constructor must always have a return type

3

A constructor is automatically called when an object is created

4

A constructor can be called explicitly like a normal method

Question 6

What is the keyword used to inherit a class in C#?

1

implements

2

extends

3

inherits

4

: (colon)

Question 7

What is the difference between == and .Equals() in C#?

1

Both are the same and compare object references

2

== compares values, whereas .Equals() compares references

3

== compares references, whereas .Equals() compares values

4

None of the above

Question 8

What will be the output of the following code?

string s1 = "Hello";
string s2 = "Hello";
Console.WriteLine(s1 == s2);
Console.WriteLine(s1.Equals(s2));

1

True True

2

False True

3

True False

4

False False

Question 9

Which of the following statements about C# interfaces is true?

1

An interface cannot be inherited by another interface

2

An interface can provide default method implementation

3

An interface can have fields

4

An interface can contain constructors

Question 10

What is the purpose of the using statement in C#?

1

It imports namespaces

2

It defines scope for disposing objects

3

It handles exceptions

4

Both 1 and 2

Question 11

What is the output of the following C# code?

using System;

class Program
{
    static void Main()
    {
        int x = 10;
        object obj = x;
        int y = (int)obj;
        Console.Write(y);
    }
}

1

Compilation error

2

10

3

Runtime error

4

NullReferenceException

Question 12

What is the correct way to define a nullable integer in C#?

1

null int num;

2

int? num = null;

3

int num = nullable;

4

nullable<int> num = null;

Question 13

Which of the following is true about C# properties?

1

Properties can have different access modifiers for get and set

2

Properties are just variables with additional syntax

3

Properties must always have both get and set

4

Properties cannot be read-only

Question 14

Which keyword is used to prevent a class from being inherited?

1

private

2

static

3

sealed

4

abstract

Question 15

Which of the following correctly implements an interface in C#?

1

interface ITest { void Show(); }
class MyClass : ITest { public void Show() { Console.WriteLine("Hello"); } }

2

interface ITest { void Show(); }
class MyClass : ITest { void Show() { Console.WriteLine("Hello"); } }

3

interface ITest { void Show(); }
class MyClass : ITest { protected void Show() { Console.WriteLine("Hello"); } }

4

interface ITest { void Show(); }
class MyClass { public void Show() { Console.WriteLine("Hello"); } }

Question 16

What will be the output of the following LINQ query?

var numbers = new List<int> { 2, 3, 4, 5 };
var result = numbers.Where(n => n % 2 == 0);
Console.WriteLine(result.Count());

1

2

4

3

2

4

3

Question 17

What will happen if you call ToString() on a null object in C#?

1

It returns an empty string

2

It depends on the object's type

3

It throws a NullReferenceException

4

It returns "null"

Question 18

What is the output of the following C# code?

async Task<int> GetNumberAsync() { return 5; }
async Task Main()
{
    Task<int> task = GetNumberAsync();
    Console.WriteLine("Before await");
    int result = await task;
    Console.WriteLine($"Result: {result}");
}

1

Random execution order

2

Result: 5
Before await

3

Before await
Result: 5

4

Compilation error

Question 19

Which of the following statements about Dictionary in C# is true?

1

Keys in a dictionary must be unique

2

A dictionary allows only string keys

3

A dictionary stores elements in a sorted order

4

All of the above

Question 20

What type of inheritance is not supported in C#?

1

Multiple Inheritance

2

Single Inheritance

3

Hierarchical Inheritance

4

Multilevel Inheritance

Question 21

Which of the following is true about abstract classes in C#?

1

Abstract classes can be instantiated.

2

Abstract classes must have at least one abstract method.

3

Interfaces and abstract classes are the same.

4

An abstract class can have concrete methods.

Question 22

Which keyword prevents method overriding in C#?

1

private

2

sealed

3

final

4

abstract

Question 23

Which of the following best describes the .NET framework?

1

A hardware component

2

An operating system

3

A development platform

4

A database management system

Question 24

Which language influenced the development of C# the most?

1

C++

2

Java

3

Python

4

PHP

Question 25

What is the primary runtime used to execute C# programs?

1

Common Language Runtime (CLR)

2

Dynamic Link Library (DLL)

3

Common Runtime Interface (CRI)

4

Java Virtual Machine (JVM)

Question 26

If you receive a 'namespace not found' error, what is the likely cause?

1

Missing semicolon

2

Typo in the class name

3

Incorrect file extension

4

Missing 'using' directive

Question 27

What will be the output of the following code?

int a = 5, b = 2;
Console.WriteLine(a / b);

1

2.5

2

Error

3

4

2

Question 28

Which operator has the highest precedence in C#?

1

+

2

*

3

=

4

()

Question 29

What does the ?? operator do in C#?

1

Performs null-coalescing

2

Checks equality

3

Checks type

4

Performs bitwise OR

Question 30

What is the result of this expression: true || false && false?

1

Cannot determine

2

false

3

true

4

Error