C# Playground

A starter program to experiment with. Edit it here, press Copy, paste it into a file called Program.cs, and run it with dotnet run Program.cs — no project needed. Lesson 2 shows how to install the .NET SDK.

List<Item> basket =
[
    new("Notebook", 3.50m, 4),
    new("Pen", 1.20m, 10),
    new("Backpack", 39.90m, 1),
];

foreach (Item item in basket.OrderByDescending(i => i.Total))
{
    Console.WriteLine($"{item.Name,-10}{item.Quantity,3} x {item.Price,6:F2} = {item.Total,7:F2}");
}

decimal sum = basket.Sum(i => i.Total);
Console.WriteLine($"Total: {sum:F2}");
Console.WriteLine($"Cheapest line: {basket.MinBy(i => i.Total)?.Name}");

record Item(string Name, decimal Price, int Quantity)
{
    public decimal Total => Price * Quantity;
}

Edit the code, copy it into Program.cs and run it with dotnet run Program.cs (.NET 10 or later). How to set up .NET

Output

Backpack    1 x  39.90 =   39.90
Notebook    4 x   3.50 =   14.00
Pen        10 x   1.20 =   12.00
Total: 65.90
Cheapest line: Pen

Ideas to try

Apply a 10% discount when the total is over 50 (lessons 12–13).
Ask the user for an item and quantity with Console.ReadLine and add it to the basket (lesson 11).
Group the items into "cheap" and "expensive" with LINQ's GroupBy (lesson 50).
Reject negative prices by adding validation to the record (lesson 40).
Save the basket to a JSON file and load it back (lesson 55).
Format prices as currency for another culture with CultureInfo (lesson 18).

Running C# without installing anything

Online playgrounds such as .NET Fiddle and SharpLab compile and run C# in your browser. They're fine for quick experiments, but some features — files, packages, and the newest language versions — may not be available there.

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