C# Tutorial

Write a method IsEven(int n) that returns a bool, and a method Describe(int n) that returns "4 is even" or "7 is odd" using IsEven.

Count how many times each word appears in the array ["apple", "mango", "apple", "kiwi", "apple"] using a Dictionary<string, int>, then print each word and its count.

Given string fullName = " ravi KUMAR ", print it as "Ravi Kumar" (trimmed, each word capitalised).

Write a method GetDisplayName(string? nickname, string fullName) that returns the nickname when it is not null or empty, otherwise the full name.

Create a Product class with Name and Price properties, a constructor, and a method PriceWithGst() that returns the price plus 18%. Create two products and print both prices with GST.

Create a Temperature class with a Celsius property that rejects values below -273.15, and a read-only Fahrenheit property calculated from Celsius.

Create a Vehicle class with a virtual Describe() returning "Vehicle with N wheels", and a Bike class that inherits it, passes 2 wheels to the base constructor and overrides Describe to add " (bike)".

Create a base class Notification with a virtual Send() returning "Sending notification", and EmailNotification / SmsNotification that override it. Loop over a list of both and print the results.

Create an abstract class Shape with an abstract double Area() and a normal method Describe() returning "Area: X" (2 decimals). Implement Circle and Square.

Create an IDiscount interface with decimal Apply(decimal price). Implement PercentDiscount(10%) and FlatDiscount(50). Apply both to a price of 500 and print the results.

Write SafeDivide(int a, int b) that returns a / b, but returns 0 and prints "Cannot divide by zero" when b is 0, by catching DivideByZeroException.

Write a generic method Swap<T>(ref T a, ref T b) that swaps two values, and test it with ints and strings.

Write a method Transform(List<string> items, Func<string, string> change) that returns a new list with change applied to every item. Call it with a method that adds "#" in front of each word.

Given List<string> names = ["Asha", "Ravi", "Meera", "Kabir"], use FindAll with a lambda to keep names longer than 4 letters, then print them.

Return the names of all Angular students in alphabetical order.

Write an async method DownloadAsync(string name, int ms) that waits ms milliseconds and returns "<name> done". Start three downloads together and print all results with Task.WhenAll.

Create a record Money(decimal Amount, string Currency). Create 100 INR, make a copy with Amount 250 using with, and print both plus whether new Money(100, "INR") equals the first one.

Write a switch expression that returns a ticket price by age: under 5 → 0, 5–17 → 100, 60 and over → 120, everyone else → 200.

Write xUnit tests for a static method bool IsValidPin(string pin) that is true only for exactly 6 digits. Use a Theory with at least 4 rows.