CODING Questions

💻 C# Concepts & Examples (Interview Ready)

This section covers important C# coding examples including LINQ, Recursion, Sorting, OOP, Delegates, and Algorithms — all commonly asked in interviews.

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🔢 Filter & Sort Numbers Using LINQ

📌 Problem

Filter numbers greater than 10 and sort them in descending order.

✅ Solution

using System;
using System.Linq;

public class Program
{
	public static void Main()
	{
		int[] arr = {1,2,4,56,8,11,23,54,28};

		var orderedRecords = arr.Where(x => x > 10).OrderByDescending(num => num);

		Console.WriteLine(String.Join(",",orderedRecords));
	}
}

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🔁 Factorial Calculation

📌 Problem

Calculate factorial of a number using iteration.

✅ Solution

using System;

public class Program
{	   
	public static int factorialCalculation(int input)
	{
	   if(input <= 1)
	   {
		   return 1;
	   }
	   else
	   {
		  int result = 1;
	      for(int i = 2; i <= input; i++)
		  {
		     result = result * i;
		  }
		  return result;
	   }
	} 
	
	public static void Main()
	{
		Console.WriteLine("Enter the  number:");
		int val = int.Parse(Console.ReadLine());
		int factVal = factorialCalculation(val);
		Console.WriteLine("The Fact is: " + factVal);
	}
}

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🔄 Bubble Sort Algorithm

📌 Problem

Sort an array using Bubble Sort.

✅ Solution

using System;

public class Program
{	// Bubble Sort
	public static int[] sortAnArray(int[] inputArr)
	{
	    for(int i = 0; i < inputArr.Length; i++)
		{
			for(int j = 0; j < inputArr.Length - 1; j++)
		    {
				if(inputArr[j] > inputArr[j+1])
				{
					int temp = inputArr[j+1];
					inputArr[j+1] = inputArr[j];
					inputArr[j] = temp;
				}
			}
		}
		return inputArr;
	} 
	
	public static void Main()
	{
        int[] arr = {3,45,76,1,24,90,44};
		int[] sortedArray = sortAnArray(arr);
		Console.WriteLine("The Sorted Array is: " + String.Join(",",sortedArray));
	}
}

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🚗 Interface Implementation

📌 Concept

Demonstrates abstraction using interfaces.

✅ Solution

using System;

public class Program
{	//  Interface Implementation
	public static void Main()
	{
        IVehicle vehicle = new Car();
		vehicle.StartEngine();
		vehicle.StopEngine();
	}
}

public class Car : IVehicle
{
  public void StartEngine()
  {
	   Console.WriteLine("Started Engine");
  }
  
  public void StopEngine()
  {
	   Console.WriteLine("Stop Engine");
  }
}

public interface IVehicle
{
	void StartEngine();
    void StopEngine();	
}

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🔢 Prime Numbers

📌 Problem

Print all prime numbers up to a given number.

✅ Solution

using System;

public class Program
{	
	public static bool IsPrime(int input)
	{
		if(input <= 1)
			return false;

		for(int i= 2; i < input; i++)
		{
			if(input % i == 0)
			{
				return false;
			}
		}
		return true;
	}
	
	//  Prime Numbers
	public static void Main()
	{
		int input = int.Parse(Console.ReadLine());

        for(int i = 2; i <= input; i++)
		{
			if(IsPrime(i))
			{
			  Console.WriteLine(i + " ");
			}
		}
	}
}

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🔁 Delegates (Custom)

📌 Concept

Demonstrates multicast delegates.

✅ Solution

using System;

public class Program
{	
	public delegate void MultiOperations(int x, int y);
	
	public static void Add(int a, int b)
	{
		Console.WriteLine("Addition:" + (a + b));
	}
	
	public static void Subtract(int a, int b)
    {
		Console.WriteLine("Subtraction:" + (a - b));
    }

    public static void Multiply(int a, int b)
    {
		Console.WriteLine("Multiplication:" + (a * b));
    }

    public static void Divide(int a, int b)
    {
        if (b != 0)
        {
			Console.WriteLine("Division:" + (a / b));
        }
        else
        {
            Console.WriteLine("Division by zero is not allowed.");
        }
    }
	
	//  Delegates
	public static void Main()
	{
      MultiOperations multiOperations = Add;

	  multiOperations += Subtract;
	  multiOperations += Multiply;
	  multiOperations += Divide;

	  Console.WriteLine("Performing operations on 20 and 5:");
      multiOperations(20, 5);
	}
}

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⚡ Built-in Delegates (Func, Action, Predicate)

📌 Concept

Modern way of using delegates in C#.

✅ Solution

using System;					

public class Program
{		
	// Built-in Delegates - Func, Action, Predicate
	public static void Main()
	{
     Func<int, int, int> Add = (a, b) => a + b;

	 Action<string> greet = (a) => Console.WriteLine("Good Morning " + a);

	 Predicate<int> isEven = x => x % 2 == 0;

	 Console.WriteLine(Add(10,23));
	 greet("Chitransh");
	 Console.WriteLine(isEven(16));
	}
}

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🔢 Fibonacci Series

📌 Problem

Generate Fibonacci sequence up to n terms.

✅ Solution

using System;					

public class Program
{		
	// Fibonacci
	public static void Main()
	{
     int n = 10;

     int[] fibbo = new int[n];

	 fibbo[0] = 0;
	 fibbo[1] = 1;

	 for(int i= 0; i < n - 2; i++)
	 {
	   	fibbo[i+2] = fibbo[i] + fibbo[i+1];
	 }

	 Console.WriteLine(String.Join(",",fibbo));
	}
}

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🧠 Key Takeaways

• LINQ simplifies filtering and sorting operations.

• Iterative logic is important for problems like factorial and Fibonacci.

• Sorting algorithms like Bubble Sort help understand fundamentals.

• Interfaces enable abstraction and loose coupling.

• Delegates (custom & built-in) are powerful for method referencing.

• Prime number logic is a common interview problem.

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These examples cover core C# fundamentals + problem-solving skills, making them highly valuable for interviews and real-world development.