C# playground

C# examples

Each one was run with .NET SDK 8.0 before it was published. Load one, change it, run it.

•  C# · Count down with a loopCopy

  // A kettle timer: print each remaining second, then the boil message.
  for (int seconds = 5; seconds >= 1; seconds--)
  {
      Console.WriteLine($"{seconds}...");
  }
  Console.WriteLine("Boiled!");
  

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•  C# · Define and call a methodCopy

  // A method with a return value, called three times.
  Console.WriteLine(Discount(2000, 15));
  Console.WriteLine(Discount(999, 0));
  Console.WriteLine(Discount(450, 50));
  
  // price and result in pence, percent as a whole number
  static int Discount(int pricePence, int percent)
  {
      return pricePence - pricePence * percent / 100;
  }
  

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•  C# · Work with a ListCopy

  // A parcel queue: add, remove, inspect.
  var parcels = new List<string> { "lamp", "books", "kettle" };
  parcels.Add("plant pot");
  parcels.Remove("books");
  
  Console.WriteLine($"{parcels.Count} parcels waiting");
  foreach (string p in parcels)
  {
      Console.WriteLine($"- {p} ({p.Length} letters)");
  }
  Console.WriteLine(parcels.Contains("kettle") ? "kettle is queued" : "no kettle");
  

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•  C# · String handlingCopy

  // Tidy up a mailing label typed in a hurry.
  string raw = "   ms. Rowan Ashby , unit 4b  ";
  string tidy = raw.Trim();
  string[] parts = tidy.Split(',');
  string name = parts[0].Trim().ToUpper();
  string unit = parts[1].Trim();
  
  Console.WriteLine(name);
  Console.WriteLine(unit);
  Console.WriteLine(name.Contains("ROWAN") ? "matched" : "not matched");
  Console.WriteLine(unit.Replace("unit", "Unit").PadLeft(12, '.'));
  

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•  C# · A class with a computed propertyCopy

  // Bus stops know how far they are from the depot.
  var stops = new List<BusStop>
  {
      new BusStop("Depot", 0),
      new BusStop("High Street", 1800),
      new BusStop("Old Mill", 4300),
  };
  
  foreach (BusStop s in stops)
  {
      Console.WriteLine($"{s.Name,-12} {s.DistanceKm:F1} km");
  }
  
  class BusStop
  {
      public string Name { get; }
      public int DistanceMetres { get; }
  
      public BusStop(string name, int distanceMetres)
      {
          Name = name;
          DistanceMetres = distanceMetres;
      }
  
      public double DistanceKm => DistanceMetres / 1000.0;
  }
  

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•  C# · LINQ query over recordsCopy

  // Pick the fastest lap per driver from a list of lap times.
  var laps = new List<Lap>
  {
      new("Ines", 1, 92.4), new("Ines", 2, 90.1), new("Ines", 3, 90.8),
      new("Tomas", 1, 91.7), new("Tomas", 2, 89.9),
  };
  
  var fastest = laps
      .GroupBy(l => l.Driver)
      .Select(g => g.MinBy(l => l.Seconds)!)
      .OrderBy(l => l.Seconds);
  
  foreach (Lap lap in fastest)
  {
      Console.WriteLine($"{lap.Driver}: lap {lap.Number} in {lap.Seconds:F1}s");
  }
  
  // type declarations go after the top-level statements
  record Lap(string Driver, int Number, double Seconds);
  

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