I’ve put together a list of 51 best C# .NET interview questions and answers for freshers that are commonly asked in interviews. If you are looking for a job in .Net, especially in C#.Net, then these questions will help you to answer correctly in the interview and get the job.
Also, if you are an interviewer and taking interviews for C# freshers, then check out all the questions and answers. When interviewing for a C# .NET position, it’s crucial to assess a candidate’s understanding of the programming language and framework, as well as their ability to apply that knowledge in real-world scenarios.
C# Interview Questions and Answers for Freshers
If you are a beginner in C# or a fresher in C#, still you should trust your practical knowledge. You should practice and prepare some practical C# topics along with these C# interview questions and answers for freshers.
If you are an experienced developer, check out the best 75 C# Interview Questions and Answers for Experienced Professionals.
1. What is C#?
C# (pronounced “C-sharp”) is a versatile, modern, object-oriented programming language developed by Microsoft. It’s part of the .NET framework and is designed to develop applications ranging from desktop to web-based. With C#, developers can create robust, secure, and scalable applications that run on the .NET framework.
2. What is .NET framework?
The .NET framework is a software development framework created by Microsoft. It provides a runtime environment, a rich class library, and support for multiple programming languages, including C#, Visual Basic, and F#.
The .NET framework simplifies the development process by providing a consistent programming model and a common set of APIs that can be used across different types of applications.
3. What are the main features of C#?
C# is known for its strong type-checking, automatic memory management (garbage collection), and support for modern programming paradigms, including object-oriented, component-oriented, and more.
Some other notable features of C# include properties, indexers, delegates, events, and the ability to create custom attributes.
4. What are the main features of .NET framework?
The .NET framework provides a runtime environment known as the Common Language Runtime (CLR), which manages the execution of code and provides services like memory management, security, and exception handling.
Additionally, the .NET framework includes a comprehensive class library that contains pre-built functions and types for common tasks like file I/O, networking, and data access.
5. What is the difference between C# and .NET?
C# is a programming language, whereas .NET is a software framework that supports multiple programming languages. C# code is compiled into an intermediate language that runs on the Common Language Runtime (CLR), which is part of the .NET framework.
6. What is an assembly in .NET?
In .NET, an assembly is a compiled code library used by applications. An assembly contains one or more files (DLLs or EXEs), and metadata that describes the types, resources, and other information about the library. Assemblies are the building blocks of .NET applications and provide a way to manage and deploy code.
7. What is the CLR in .NET?
The Common Language Runtime (CLR) is the execution engine of the .NET framework. It provides a range of services, including memory management, security, and exception handling, that enable developers to create reliable and secure applications. The CLR also provides just-in-time (JIT) compilation, which converts intermediate language code into native machine code at runtime.
8. What is the difference between value types and reference types in C#?
Value types are stored on the stack and contain the actual data, whereas reference types are stored on the heap and contain a reference to the data. Value types include primitive types like int, float, and char, as well as structs. Reference types include classes, objects, arrays, and strings.
The main difference between value types and reference types in C# lies in how they are stored in memory. Value types are stored in the stack, and their value is stored directly in the memory location. On the other hand, reference types are stored in the heap, and the memory location contains a reference to the actual data.
Here is an example with code to demonstrate the difference between value types and reference types in C#:
// Example of value types and reference types in C#
class Program
{
static void Main()
{
// Value type example
int a = 5;
int b = a; // b is a copy of a
b = 10; // changing b does not affect a
Console.WriteLine(a); // Output: 5
// Reference type example
int[] arr1 = { 1, 2, 3 };
int[] arr2 = arr1; // arr2 references the same array as arr1
arr2[0] = 10; // changing arr2 affects arr1
Console.WriteLine(arr1[0]); // Output: 10
}
}
9. What is polymorphism in C#?
Polymorphism is one of the fundamental concepts of object-oriented programming. In C#, polymorphism enables a single function or method to work in different ways based on the input or context. There are two types of polymorphism in C#: compile-time polymorphism (method overloading) and runtime polymorphism (method overriding). In C#, polymorphism can be achieved using method overriding or interfaces.
// Example of polymorphism in C#
class Animal
{
public virtual void MakeSound()
{
Console.WriteLine("Animal makes a sound");
}
}
class Dog : Animal
{
public override void MakeSound()
{
Console.WriteLine("Dog barks");
}
}
class Cat : Animal
{
public override void MakeSound()
{
Console.WriteLine("Cat meows");
}
}
class Program
{
static void Main()
{
Animal myAnimal = new Animal();
myAnimal.MakeSound();
Dog myDog = new Dog();
myDog.MakeSound();
Cat myCat = new Cat();
myCat.MakeSound();
}
}
// Output:
// Animal makes a sound
// Dog barks
// Cat meows
10. What is inheritance in C#?
Inheritance is one of the fundamental concepts of object-oriented programming in C#. It allows a class (derived class) to inherit attributes and behaviors from another class (base class). The derived class can also override or extend the behaviors of the base class.
// Example of inheritance in C#
class Animal
{
public void Eat()
{
Console.WriteLine("Eating...");
}
}
class Dog : Animal
{
public void Bark()
{
Console.WriteLine("Barking...");
}
}
class Program
{
static void Main()
{
Dog myDog = new Dog();
myDog.Eat();
myDog.Bark();
}
}
// Output:
// Eating...
// Barking...
11. What is encapsulation in C#?
Encapsulation is one of the four fundamental OOP concepts. The other three are inheritance, polymorphism, and abstraction. It is the technique of making the fields in a class private and providing access to them via public methods. It’s a protective barrier that keeps the data safe within the object and prevents outside code from directly accessing it.
// Example of encapsulation in C#
class BankAccount
{
private double balance;
public void Deposit(double amount)
{
if (amount > 0)
balance += amount;
}
public void Withdraw(double amount)
{
if (amount > 0 && amount <= balance)
balance -= amount;
}
public double GetBalance()
{
return balance;
}
}
class Program
{
static void Main()
{
BankAccount account = new BankAccount();
account.Deposit(1000);
account.Withdraw(500);
Console.WriteLine(account.GetBalance()); // Output: 500
}
}
12. What is an interface in C#?
An interface defines a contract for classes that implement it. It can contain declarations for methods, properties, events, and indexers, but no implementations. A class that implements an interface must provide an implementation for all the members declared in the interface.
// Example of an interface in C#
interface IDisplay
{
void Display();
}
class MyClass : IDisplay
{
public void Display()
{
Console.WriteLine("Displaying...");
}
}
class Program
{
static void Main()
{
MyClass obj = new MyClass();
obj.Display(); // Output: Displaying...
}
}
13. What is a delegate in C#?
A delegate is a type that represents references to methods with a particular parameter list and return type. Delegates are used to define callback methods and can be used to create custom events in C#.
// Example of a delegate in C#
delegate int MyDelegate(int x, int y);
class MathOperations
{
public static int Add(int x, int y)
{
return x + y;
}
public static int Subtract(int x, int y)
{
return x - y;
}
}
class Program
{
static void Main()
{
MyDelegate d1 = MathOperations.Add;
MyDelegate d2 = MathOperations.Subtract;
Console.WriteLine(d1(5, 3)); // Output: 8
Console.WriteLine(d2(5, 3)); // Output: 2
}
}
14. What are events in C#?
Events are a way to provide notifications. They are based on the delegate type and are used to define custom notifications that can be raised by an object when something of interest happens.
// Example of an event in C#
class Counter
{
private int threshold;
private int total;
public event EventHandler ThresholdReached;
public Counter(int passedThreshold)
{
threshold = passedThreshold;
}
public void Add(int x)
{
total += x;
if (total >= threshold)
{
ThresholdReached?.Invoke(this, EventArgs.Empty);
}
}
}
class Program
{
static void Main()
{
Counter c = new Counter(10);
c.ThresholdReached += c_ThresholdReached;
c.Add(5);
c.Add(6);
}
static void c_ThresholdReached(object sender, EventArgs e)
{
Console.WriteLine("Threshold reached.");
}
}
15. What is an exception in C#?
An exception is a way to handle errors or unexpected conditions that occur during the execution of a program. C# provides a structured way to handle exceptions using try, catch, and finally blocks.
16. What is a namespace in C#?
A namespace is a logical grouping of related classes, interfaces, and other types. It provides a way to organize code and prevent name conflicts between types.
// Example of a namespace in C#
namespace MyNamespace
{
class MyClass
{
public void Display()
{
Console.WriteLine("Displaying...");
}
}
}
class Program
{
static void Main()
{
MyNamespace.MyClass obj = new MyNamespace.MyClass();
obj.Display(); // Output: Displaying...
}
}
17. What is LINQ in C#?
LINQ (Language Integrated Query) is a powerful feature in C# that enables developers to write queries for collections of data using a SQL-like syntax. LINQ supports querying collections, databases, XML, and more.
// Example of LINQ in C#
using System.Linq;
class Program
{
static void Main()
{
int[] numbers = { 1, 2, 3, 4, 5 };
var evenNumbers = from num in numbers
where num % 2 == 0
select num;
foreach (int num in evenNumbers)
{
Console.WriteLine(num);
}
}
}
// Output: 2 4
18. What is the difference between a class and an object in C#?
A class is a blueprint for creating objects and defining the properties, methods, and events that the objects will have. An object is an instance of a class created using the new keyword in C#.
19. What is a constructor in C#?
A constructor is a special method in a class that is used to initialize the object. Constructors have the same name as the class and can be overloaded to provide different ways to initialize the object.
// Example of a constructor in C#
class Person
{
string name;
int age;
// Constructor
public Person(string n, int a)
{
name = n;
age = a;
}
public void DisplayInfo()
{
Console.WriteLine($"Name: {name}, Age: {age}");
}
}
class Program
{
static void Main()
{
// Creating an instance of Person using constructor
Person person = new Person("John", 25);
person.DisplayInfo();
}
}
// Output: Name: John, Age: 25
20. What is garbage collection in C#?
Garbage collection is a feature of the CLR (Common Language Runtime) that automatically reclaims memory occupied by objects that are no longer in use.
There is no specific example to demonstrate garbage collection as it is a background process handled by the CLR. However, you can force garbage collection using the GC.Collect() method, but it is generally not recommended as it can have performance implications.
21. What is a destructor in C#?
A destructor is a special method in a class that is used to clean up resources before the object is garbage collected. Destructors are called automatically by the garbage collector and should not be called explicitly.
22. What is the difference between a static class and an instance class in C#?
A static class is a class that cannot be instantiated and its members can be accessed without creating an instance of the class. An instance class is a class that can be instantiated and its members are accessed through instances of the class.
23. What is the difference between a method and a function in C#?
In C#, a method is a function that is associated with an object, whereas a function is a standalone procedure. Methods are defined inside classes and can access the data and other methods of the class.
24. What is the difference between a property and a field in C#?
A property is a member of a class that provides access to a field, and may include logic to validate the data. A field is a variable that is defined inside a class and stores data.
25. What is the difference between a public and private member in C#?
A public member can be accessed from anywhere, whereas a private member can only be accessed from within the class. This allows developers to control the visibility of the data and methods of a class.
26. What is the difference between an abstract class and an interface in C#?
An abstract class can have both abstract and concrete methods, whereas an interface can only have abstract methods. Abstract classes are used to define a common base class for derived classes, whereas interfaces are used to define a contract that must be implemented by any class that implements the interface.
27. What is the difference between a for loop and a while loop in C#?
A for loop in C# is used when you know the number of iterations in advance. It has three parts: initialization, condition, and increment/decrement. A while loop is used when the number of iterations is not known in advance and depends on a condition being true.
// Example of a for loop
for (int i = 0; i < 5; i++)
{
Console.WriteLine(i);
}
// Example of a while loop
int j = 0;
while (j < 5)
{
Console.WriteLine(j);
j++;
}
28. What is an array in C#?
An array is a collection of elements of the same type that are stored in contiguous memory locations in C#. Arrays are zero-based, meaning that the first element is at index 0.
// Example of an array in C#
int[] numbers = { 1, 2, 3, 4, 5 };
for (int i = 0; i < numbers.Length; i++)
{
Console.WriteLine(numbers[i]);
}
29. What is a string in C#?
A string is a sequence of characters that represents text. In C#, the string type is used to represent strings, and it provides a range of methods for working with text.
// Example of a string in C#
string greeting = "Hello, world!";
Console.WriteLine(greeting);
30. What is a List in C#?
A C# List is a collection of elements that can grow or shrink in size dynamically. It’s part of the System.Collections.Generic namespace and provides methods for adding, removing, and searching elements.
// Example of a List in C#
List<int> numbers = new List<int> { 1, 2, 3, 4, 5 };
numbers.Add(6);
numbers.Remove(3);
foreach (int number in numbers)
{
Console.WriteLine(number);
}
31. What is the using statement in C#?
The using statement in C# is used to include a namespace in your program. It can also be used to create a scope for an object, ensuring that the object’s Dispose method is called when the scope is exited.
// Example of a using statement for a namespace
using System;
// Example of a using statement for an object
using (StreamWriter writer = new StreamWriter("file.txt"))
{
writer.WriteLine("Hello, world!");
}
Here is another example:
// Example of using statement in C#
using System;
using System.IO;
class Program
{
static void Main()
{
using (StreamWriter writer = new StreamWriter("example.txt"))
{
writer.WriteLine("Hello, World!");
}
}
}
32. What is the else if statement in C#?
The C# else if statement is used to test multiple conditions in a sequence. If the condition of the if statement is false, the program will check the condition of the else if statement. If the condition of the else if statement is true, the statements inside the else if block will be executed. If the condition of the else if statement is also false, the program will move on to the next else if or else block, if any.
// Example of else if statement in C#
int num = 5;
if (num < 0)
{
Console.WriteLine("Number is negative");
}
else if (num == 0)
{
Console.WriteLine("Number is zero");
}
else
{
Console.WriteLine("Number is positive");
}
// Output: Number is positive
33. What is the switch statement in C#?
The switch statement in C# is used to test a variable against a list of values and execute the corresponding block of code. The break statement is used to exit the switch block once the match is found.
// Example of switch statement in C#
int num = 3;
switch (num)
{
case 1:
Console.WriteLine("One");
break;
case 2:
Console.WriteLine("Two");
break;
case 3:
Console.WriteLine("Three");
break;
default:
Console.WriteLine("Other");
break;
}
// Output: Three
34. What is the difference between break and continue in C#?
The break statement is used to terminate the loop or switch statement and resume execution at the next statement following the loop or switch in C#. The continue statement is used to skip the rest of the code inside the loop for the current iteration and move to the next iteration of the loop.
// Example of break in C#
for (int i = 0; i < 5; i++)
{
if (i == 3)
break;
Console.WriteLine(i);
}
// Output: 0 1 2
// Example of continue in C#
for (int i = 0; i < 5; i++)
{
if (i == 3)
continue;
Console.WriteLine(i);
}
// Output: 0 1 2 4
35. What is method overloading in C#?
Method overloading in C# allows a class to have multiple methods with the same name but different parameter lists. The correct method to call is determined at compile-time based on the number and type of arguments passed.
// Example of method overloading in C#
class MathOperations
{
public int Add(int a, int b)
{
return a + b;
}
public double Add(double a, double b)
{
return a + b;
}
}
class Program
{
static void Main()
{
MathOperations math = new MathOperations();
Console.WriteLine(math.Add(2, 3)); // Output: 5
Console.WriteLine(math.Add(2.5, 3.5)); // Output: 6
}
}
36. What is a static method in C#?
A static method in C# belongs to the class rather than any specific instance of the class. It can be called on the class itself, without creating an instance.
// Example of a static method in C#
class MathOperations
{
public static int Add(int a, int b)
{
return a + b;
}
}
class Program
{
static void Main()
{
int result = MathOperations.Add(2, 3);
Console.WriteLine(result); // Output: 5
}
}
38. What are properties in C#?
Properties in C# are a way to expose fields of a class in a controlled manner. They allow you to encapsulate the field and provide get and set accessors to read and write the value of the field.
// Example of properties in C#
class Person
{
private string name;
public string Name
{
get { return name; }
set { name = value; }
}
}
class Program
{
static void Main()
{
Person person = new Person();
person.Name = "John";
Console.WriteLine(person.Name); // Output: John
}
}
39. What is a readonly field in C#?
A readonly field in C# is a field that can only be assigned a value during its declaration or within the constructor of the class it belongs to. Once a readonly field is assigned a value, it cannot be modified.
// Example of a readonly field in C#
class MyClass
{
public readonly int MyField;
public MyClass(int value)
{
MyField = value;
}
}
class Program
{
static void Main()
{
MyClass obj = new MyClass(5);
Console.WriteLine(obj.MyField); // Output: 5
// The following line would cause a compilation error
// obj.MyField = 10;
}
}
41. What is the null value in C#?
The null value represents an absence of a value or an undefined value. In C#, a reference type variable can be assigned the null value to indicate that it does not reference any object. A value type variable cannot be assigned the null value directly, but it can be made nullable by using the Nullable <T> structure or the ? modifier.
// Example of null value in C#
string str = null;
Console.WriteLine(str); // Output:
int? nullableInt = null;
Console.WriteLine(nullableInt); // Output:
42. What is the purpose of the try and catch blocks in C#?
The try and catch blocks are used for exception handling in C#. The try block contains the code that might throw an exception, and the catch block contains the code that will be executed if an exception is thrown.
// Example of try and catch blocks in C#
class Program
{
static void Main()
{
try
{
int num = int.Parse("abc");
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
}
// Output: Input string was not in a correct format.
43. What is exception handling in C#?
Exception handling is a mechanism to handle runtime errors in a program. In C#, exception handling is done using try, catch, finally, and throw statements.
// Example of exception handling in C#
class Program
{
static void Main()
{
try
{
int num = int.Parse("abc");
}
catch (FormatException ex)
{
Console.WriteLine(ex.Message);
}
finally
{
Console.WriteLine("This block is always executed.");
}
}
}
// Output:
// Input string was not in a correct format.
// This block is always executed.
44. What are loops in C#?
Loops in C# are used to execute a block of code multiple times. There are several types of loops in C#, such as for loop, while loop, do-while loop, and foreach loop.
// Example of a for loop in C#
for (int i = 0; i < 5; i++)
{
Console.WriteLine(i);
}
// Output: 0 1 2 3 4
45. What is an array in C#?
An array is a collection of elements of the same type, stored in contiguous memory locations. In C#, you can declare and initialize an array using the new keyword.
// Example of an array in C#
int[] numbers = new int[5] { 1, 2, 3, 4, 5 };
foreach (int num in numbers)
{
Console.WriteLine(num);
}
// Output: 1 2 3 4 5
46. What is the difference between string and StringBuilder in C#?
The main difference between string and StringBuilder in C# lies in their mutability. string is immutable, which means that once a string object is created, its value cannot be changed. On the other hand, StringBuilder is mutable, which means that its value can be changed without creating a new object.
// Example of string and StringBuilder in C#
using System.Text;
class Program
{
static void Main()
{
// String example
string str1 = "Hello";
str1 += ", World!"; // This creates a new string object
// StringBuilder example
StringBuilder sb = new StringBuilder("Hello");
sb.Append(", World!"); // This modifies the existing StringBuilder object
}
}
47. What is the null keyword in C#?
The null keyword in C# represents the absence of a value or an object. It can be assigned to any reference type, but it cannot be assigned to a value type.
// Example of null in C#
class Program
{
static void Main()
{
string str = null; // Valid
// int num = null; // Invalid, because int is a value type
}
}
48. What is the ?? operator in C#?
The ?? operator in C# is called the null-coalescing operator. It is used to return the left-hand operand if it is not null, otherwise it returns the right-hand operand.
// Example of ?? operator in C#
class Program
{
static void Main()
{
string str = null;
string result = str ?? "Default"; // Returns "Default" because str is null
}
}
49. What is the virtual keyword in C#?
The virtual keyword in C# is used to declare a method that can be overridden in derived classes.
// Example of virtual keyword in C#
class Shape
{
public virtual void Draw()
{
Console.WriteLine("Drawing a shape");
}
}
class Circle : Shape
{
public override void Draw()
{
Console.WriteLine("Drawing a circle");
}
}
50. What is the override keyword in C#?
The override keyword in C# is used to override a virtual or abstract method in a derived class.
// Example of override keyword in C#
class Shape
{
public virtual void Draw()
{
Console.WriteLine("Drawing a shape");
}
}
class Circle : Shape
{
public override void Draw()
{
Console.WriteLine("Drawing a circle");
}
}
51. What are extension methods in C#?
Extension methods in C# are a way to add new methods to existing types without modifying the original type. They are defined as static methods in a static class, and they use the this keyword as a modifier on the first parameter, which specifies the type that the method will operate on. This allows the method to be called as if it were an instance method on that type.
Here is an example to illustrate how to create and use extension methods in C#:
// Example of extension methods in C#
public static class StringExtensions
{
// Extension method to count the number of words in a string
public static int WordCount(this string str)
{
return str.Split(new char[] { ' ', '.', '?' }, StringSplitOptions.RemoveEmptyEntries).Length;
}
}
class Program
{
static void Main()
{
string example = "This is an example string.";
// Use the extension method
int wordCount = example.WordCount();
Console.WriteLine(wordCount); // Output: 5
}
}
Conclusion
Whether you are a fresher preparing for an interview or an interviewer looking for questions to ask, these C# interview questions and answers for freshers will help you to click on the interviews. I hope these interview questions and answers for freshers in C# will be helpful to you.
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Bijay Kumar is a renowned software engineer, accomplished author, and distinguished Microsoft Most Valuable Professional (MVP) specializing in SharePoint. With a rich professional background spanning over 15 years, Bijay has established himself as an authority in the field of information technology. He possesses unparalleled expertise in multiple programming languages and technologies such as ASP.NET, ASP.NET MVC, C#.NET, and SharePoint, which has enabled him to develop innovative and cutting-edge solutions for clients across the globe. Read more…