20 Common .NET Coding Interview Questions

Preparing for a .NET interview can be a challenging yet rewarding experience. In this tutorial, we will cover 20 common .NET coding interview questions frequently asked in interviews. These questions span various aspects of .NET development, including C#, ASP.NET, and general programming concepts. Let’s dive in.

Common .NET Coding Interview Questions with Answers

As we begin to explore Common .NET Coding Interview Questions with Answers, let’s first deepen our understanding of key concepts in C# and .NET development.

Question: How do ref and out parameters differ in C#?

Answer:
In C#, both ref and out parameters allow a method to modify the value of the parameter. However, the key difference lies in initialization. ref parameters must be initialized before being passed to the method, while out parameters do not require prior initialization; the method is responsible for assigning a value.

// Example of ref parameter
void ModifyWithRef(ref int x)
{
    x += 10;
}

// Example of out parameter
void ModifyWithOut(out int y)
{
    y = 20;
}

Question: Describe the distinction between String and StringBuilder in C#.

Answer:
String is immutable in C#, meaning once created, it cannot be modified. StringBuilder, on the other hand, is mutable, allowing for efficient manipulation of string data.

// Example using String
string immutableString = "Hello, ";
immutableString += "world!";  // Creates a new string

// Example using StringBuilder
StringBuilder mutableString = new StringBuilder("Hello, ");
mutableString.Append("world!");  // Modifies the existing StringBuilder

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

Answer:
In C#, the using statement helps manage resources automatically. It ensures proper cleanup of IDisposable objects, such as streams or database connections, after use.

// Example using FileStream with using statement
using (FileStream fileStream = new FileStream("example.txt", FileMode.Open))
{
    // Perform operations with fileStream
} // fileStream is automatically disposed

Question: What sets apart IEnumerable and IEnumerator in C#?

Answer:
IEnumerable represents a collection of objects that can be enumerated, and IEnumerator provides a mechanism for iterating through the elements of a collection.

// Example using IEnumerable and IEnumerator
IEnumerable<int> numbers = new List<int> { 1, 2, 3, 4, 5 };

foreach (int num in numbers)
{
    Console.WriteLine(num);
}

Question: Explain the concept of boxing and unboxing in C#.

Answer:
Boxing is the process of converting a value type to a reference type, and unboxing is the reverse process. It can impact performance, so it’s essential to be aware of when it occurs.

// Example of boxing and unboxing
int intValue = 42;
object boxedValue = intValue;   // Boxing
int unboxedValue = (int)boxedValue; // Unboxing

Question: In C#, what distinguishes an abstract class from an interface?

Answer:
An abstract class can have both abstract and non-abstract methods, while an interface can only have abstract methods. A class can implement multiple interfaces, but it can inherit from only one abstract class.

// Example of abstract class and interface
abstract class Shape
{
    public abstract void Draw();
}

interface IDrawable
{
    void Draw();
}

Question: Explain the concept of polymorphism in C#.

Answer:
Polymorphism makes it possible to treat different types of objects as if they are of the same base type. This involves changing methods and overloading operators.

// Example of polymorphism
class Shape
{
    public virtual void Draw()
    {
        Console.WriteLine("Drawing a shape");
    }
}

class Circle : Shape
{
    public override void Draw()
    {
        Console.WriteLine("Drawing a circle");
    }
}

Question: What is encapsulation in C#?

Answer:
Encapsulation is the bundling of data and methods that operate on the data into a single unit, known as a class. It helps in hiding the implementation details from the outside world.

// Example of encapsulation
class Person
{
    private string name;

    public string GetName()
    {
        return name;
    }

    public void SetName(string newName)
    {
        name = newName;
    }
}

Question: Differentiate between method overloading and method overriding.

Answer:
Method overloading involves having multiple methods with the same name but different parameters in the same class. Method overriding occurs when a derived class provides a specific implementation for a method that is already defined in its base class.

// Example of method overloading and overriding
class Calculator
{
    public int Add(int a, int b)
    {
        return a + b;
    }

    public double Add(double a, double b)
    {
        return a + b;
    }
}

class AdvancedCalculator : Calculator
{
    public override int Add(int a, int b)
    {
        return a + b * 2;
    }
}

Question: What is the purpose of the base keyword in C#?

Answer: In C#, a derived class uses the base keyword to access members of the base class. Developers often employ it to invoke the base class constructor or access overridden methods.

// Example using base keyword
class Animal
{
    public void Eat()
    {
        Console.WriteLine("Animal is eating");
    }
}

class Dog : Animal
{
    public void Bark()
    {
        Console.WriteLine("Dog is barking");
    }

    public void EatAndBark()
    {
        base.Eat();  // Calling base class method
        Bark();
    }
}

Question: What is ASP.NET MVC, and how does it differ from ASP.NET Web Forms?

Answer:
ASP.NET MVC is a way of building websites that separates the code into three parts: Model (for data), View (for the user interface), and Controller (for managing user input). This makes it organized and easier to maintain.

On the other hand, ASP.NET Web Forms bundles everything together on a page, providing a simpler approach. It speeds up development but might result in slightly less organization.

So, in a nutshell, ASP.NET MVC is like having separate rooms for different tasks, while ASP.NET Web Forms is more like having everything in one room. The choice depends on how you prefer to organize your work.

Question: Explain the purpose of ViewState in ASP.NET.

Answer:
In ASP.NET WebForms, ViewState persists state info between postbacks. It helps the server remember the values of controls on the page across requests.

Question: Compare the features of GET and POST requests in ASP.NET.

Answer:
In ASP.NET, both GET and POST are HTTP request methods. They act as a carrier to exchange data with the server. GET adds the data to the trailing part of the URL, while POST patches the data within the body of the HTTP packet.

Question: What is the role of the Global.asax file in ASP.NET?

Answer:
The Global.asax file in ASP.NET contains application-level events and settings. It is used to handle application-level events like Application_Start, Application_End, Session_Start, and Session_End.

Question: Explain the purpose of the App_Code folder in ASP.NET.

Answer:
In ASP.NET, the App_Code folder stores source code files auto-compiled at runtime. Code here can be shared across multiple pages and components for convenience.

Let’s now check out a few generic questions instead of just focusing on the NET coding interview questions.

Question: In general programming, how does an abstract class differ from an interface?

Answer:
An abstract class can have both abstract and non-abstract methods, and a class can inherit from only one abstract class. An interface can only have abstract methods, and a class can implement multiple interfaces.

Question: What is the purpose of the try-catch block in exception handling?

Answer:
The try-catch block is used for handling exceptions in a controlled manner. Code within the try block is monitored for exceptions, and if an exception occurs, it is caught and handled in the catch block.

Question: Explain the concept of threading in Dot NET.

Answer:
Threading allows multiple operations to run concurrently. In .NET, the System. Threading namespace provides classes for creating and managing threads.

Question: What is dependency injection, and why is it beneficial?

Answer:
Dependency injection is a design pattern where dependencies are injected into a class rather than created within the class. It promotes loose coupling, making the code more maintainable and testable.

Question: How does garbage collection work in .NET?

Answer:
Garbage collection in .NET automatically reclaims memory occupied by objects that are no longer in use. The Common Language Runtime (CLR) is responsible for managing the garbage collection process.

Don’t leave without checking these out.

• 15 C# Interview Questions for Your Quick Ref
• Test C# Programming Skills – 15 Questions on Classes for Beginners
• 20 C# Programming Questions on Object-Oriented Concepts
• 50 Must Know C# Coding Interview Questions for Developers

Preparing for a .NET coding interview requires a solid understanding of C#, OOP, ASP.NET, and general programming concepts. This tutorial covered 20 common coding interview questions with detailed answers to help you.

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Enjoy coding,
TechBeamers.