C# Junior Developer Interview Questions

What is the relationship between an interface and a class

A class is like a blueprint for creating objects. It tells us what properties and actions those objects will have. An interface is like a contract that classes can sign. It says, "If you want to be this type of thing, you must be able to do these actions." A class can promise to follow the rules of an interface by implementing it. When a class implements an interface, it must provide code for all the actions the interface requires. Interfaces help different classes work together, even if they are different types. They make it easy to use objects interchangeably, as long as they follow the same rules. I n simple terms, classes are like blueprints for objects, while interfaces are like agreements that classes can sign to promise they'll behave a certain way.

What is a method in C# and how do you define and call one? Can you explain parameters and return types in methods with examples?

A method in C# is a code block that performs a specific task. You define a method using the public or private access modifier, followed by the return type (void if no return value), the method name, and parameters if any. For example, public void PrintMessage(string message) { Console.WriteLine(message); }. To call a method, you use its name followed by parentheses and provide any required arguments. For example, PrintMessage('Hello!');

Define name spaces

A namespace is a way to organize code elements such as classes, functions, and variables into logical groups to prevent naming conflicts. For example, you might have multiple classes named "Logger" in different parts of your codebase. To differentiate between them, you can place each class in a separate namespace namespace Logging { public class Logger { // Logger implementation } } csharp namespace Networking { public class Logger { // Logger implementation } } Then, when you want to use one of these classes, you specify the namespace along with the class name to disambiguate: Logging.Logger logger1 = new Logging.Logger(); Networking.Logger logger2 = new Networking.Logger(); Namespaces also help with code organization and readability, making it easier to understand the structure of a codebase and locate specific code elements. They promote code reusability and maintainability by providing a clear separation of concerns.

What is an abstract class

An abstract class in C# is a class that cannot be instantiated on its own, but can be used as a base for other classes. It serves as a blueprint for other classes to inherit from, providing common functionality and defining methods that subclasses must implement. Heres an example of accessing an abstract class: public abstract class Animal { public abstract void MakeSound(); // Abstract method without implementation public void Eat() { Console.WriteLine("Animal is eating."); // Concrete method with implementation } } public class Dog : Animal { public override void MakeSound() { Console.WriteLine("Woof!"); // Implementation of abstract method } } public class Cat : Animal { public override void MakeSound() { Console.WriteLine("Meow!"); // Implementation of abstract method } } class Program { static void Main(string[] args) { Animal dog = new Dog(); Animal cat = new Cat(); dog.MakeSound(); // Output: Woof! cat.MakeSound(); // Output: Meow! } }

What are the different data types available in C# and can you provide examples of each?

C# supports various data types such as int for integers, double for floating-point numbers, string for text, and bool for boolean values. For example, int age = 25;, double price = 19.99;, string name = 'John';, and bool isTrue = true;

What are the Request methods of CRUD functions

Create (Post), Read (Get), Update(put), Delete

What is debugging and how do you debug C# code in Visual Studio? Can you explain the process of setting breakpoints and stepping through code?

Debugging is the process of identifying and fixing errors or bugs in a program. In Visual Studio, you can set breakpoints in your code to pause execution at specific points and inspect the state of variables and objects. You can then use the debugging tools to step through the code line by line and identify the source of the problem. For example, you can set breakpoints by clicking in the margin next to a line of code, and then start debugging by clicking the 'Start Debugging' button or pressing F5.

Dictionaries example

Dictionaries are mutable which means their state can be modified after they are created. This means you can add, or modify the elements of a dictionary after it is created. For example, you can use the Add() method of the System.Collections.Generic.Dictionary<TKey, TValue> class to add new key-value pairs to a dictionary, or you can use the Remove() method to remove elements from a dictionary- While mutable dictionaries can be useful in some cases, it is generally considered good pratice to use immutable data structures wherever possible. In .NET, you can use the System.Immutable.ImmutableDictionary<TKey, TValue> class to create an immutable dictionary.

What is encapsulation, and how is it utilized in object-oriented programming? Can you provide an example?

Encapsulation is a concept in OOP that involves bundling data (variables) and methods (functions) that operate on the data into a single unit (class). It helps in data hiding and abstraction. For example, a Car class may encapsulate variables like speed and fuelLevel, along with methods like accelerate() and refuel()

What are exceptions in C# and how do you handle them using try, catch, and finally blocks? Can you provide an example of exception handling?

Exceptions are unexpected or exceptional events that occur during program execution. In C#, exceptions are handled using try, catch, and finally blocks. The try block contains the code that may throw an exception, the catch block catches and handles the exception, and the finally block is used to execute code that should always run, regardless of whether an exception occurred. For example: try { int result = 10 / 0; // Division by zero } catch (DivideByZeroException ex) { Console.WriteLine('Error: ' + ex.Message); } finally { Console.WriteLine('Finally block executed.'); } ```"

IEnumerable vs IEunumerator

IEnumerable is an interface that represents a collection of objects that can be enumerated, while IEnumerator is an interface that provides methods for iterating through a collection. IEnumerable provides a way to obtain an IEnumerator object, which is then used to iterate over the elements of the collection manually

How do you read user input from the console in C#? Can you explain the purpose of the Console.WriteLine() and Console.ReadLine() methods with examples?

In C#, you can read user input from the console using the Console.ReadLine() method, which reads a line of text entered by the user and returns it as a string. You can use the Console.WriteLine() method to display output to the console. This method accepts a string argument and writes it to the console followed by a newline character. For example: Console.WriteLine('Enter your name:'); string name = Console.ReadLine(); Console.WriteLine('Hello, ' + name + '!'); ```"

What is the relationship between a class and an object

In simple terms, you can think of a class as a recipe, while an object is a specific dish prepared according to that recipe. The class defines the ingredients and instructions (properties and methods), while the object is the actual dish you can see, touch, and interact with.

What is C#?

It is a strong typing, object-oriented programming language created by Microsoft that runs on the .NET Framework. Used for building a wide range of software applications, including desktop, web, mobile, and gaming applications, among others.

What is the difference between a list and an array

Lists are more commonly used in scenarios where the size of the collection may change frequently, or where you need to perform a lot of insertions or deletions.

List the differences between Static, Public, and Void

Static - It's a keyword that declares the Main method as the global one and can be called without creating a new instance of the class. Public - It's an access modifier keyword that tells the compiler that anyone can access the Main method. Void - It's a type modifier keyword that states that the Main method doesn't return any value.

What are strings in C# and how do you manipulate them? Can you provide an example of string concatenation and finding the length of a string?

Strings in C# are sequences of characters enclosed in double quotes. You can manipulate strings using various methods and operators. For example, you can concatenate two strings using the + operator or the String.Concat() method. The Length property returns the number of characters in a string. For example: string firstName = 'John'; string lastName = 'Doe'; string fullName = firstName + ' ' + lastName; int length = fullName.Length; Console.WriteLine(fullName); // Output: 'John Doe' Console.WriteLine(length); // Output: 8 ```"

How does the foreach loop work in C# and when would you use it? Can you explain the purpose of the List<T> class and provide an example?

The foreach loop in C# is used to iterate over elements in a collection, such as arrays or lists. It simplifies the process of iterating through each element in the collection without having to manually manage an index variable. You would use it when you want to perform an operation on each item in a collection. The List<T> class in C# is a generic collection that can store elements of a specified type. It provides methods for adding, removing, and accessing elements in the list. For example: List<int> numbers = new List<int>() { 1, 2, 3, 4, 5 }; foreach (int num in numbers) { Console.WriteLine(num); } ```"

When faced with a programming challenge, what approach do you typically take to solve it? Can you walk me through an example of how you've tackled a problem in the past?

When faced with a programming challenge, I typically start by breaking down the problem into smaller, more manageable tasks. I analyze the requirements and identify the inputs, outputs, and any constraints or edge cases. Then, I develop a plan or algorithm to solve each sub-problem, implementing and testing each step iteratively until the overall solution is complete and meets the requirements. For example, in a recent project, I was tasked with implementing a sorting algorithm. I began by researching different sorting algorithms, then I chose one that suited the requirements and implemented it step by step, testing along the way to ensure correctness and efficiency.

Float vs Double

float = less memory and faster operations, double = more precise and can hold bigger

How to find if the given input is a palindrome?

function Palindrome(str){ for (let i = 0; i < str.length / 2; i++){ if (str[i] != str[str.length - i - 1]) return false; } return true; }

How to reverse a string

function reverseString(str) { let reversed = ''; for (let i = str.length - 1; i >= 0; i--) { reversed += str[i]; } return reversed; } console.log(reverseString("hello")); // Output: "olleh"

How to find if a positive integer is a prime number or not

public static bool IsPrime(int number) { if (number <= 1) return false; if (number == 2) return true; if (number % 2 == 0) return false; int sqrt = (int)Math.Sqrt(number); for (int i = 3; i <= sqrt; i += 2) { if (number % i == 0) return false; } return true; }