C# 14 cheatsheet

C# 14: Records, classes and pattern matching

12 common C# 14 tasks.

Declare an immutable data type

A record gives you value equality, ToString and deconstruction.

public record Person(string Name, int Age);

var ada = new Person("Ada", 36);

Create a modified copy and leave the original unchanged.

var older = ada with { Age = 37 };

Put constructor parameters on the type declaration and use them in members.

public class Greeter(string name)
{
    public string Greet() => $"Hello, {name}!";
}

Force callers to set a property, and make it settable only during initialization.

public class User
{
    public required string Email { get; init; }
    public string? Nickname { get; set; }
}

C# 14: use the field keyword to reach the compiler-generated backing field.

public string Name
{
    get;
    set => field = value.Trim();
} = "";

A compact switch that returns a value, with a default.

string label = score switch
{
    >= 90 => "A",
    >= 80 => "B",
    _ => "C"
};

Check a type and bind it to a variable in one expression.

if (shape is Circle { Radius: > 10 } c)
    Console.WriteLine(c.Radius);

Match arrays and lists by length and contents.

var result = numbers switch
{
    [] => "empty",
    [var only] => $"one: {only}",
    [var first, .., var last] => $"{first}..{last}"
};

A named set of constants, and parsing one from text.

enum Status { Draft, Published, Archived }

var status = Enum.Parse<Status>("Published");

A static method in a static class, with this on its first parameter.

public static class StringExtensions
{
    public static bool IsBlank(this string? s) => string.IsNullOrWhiteSpace(s);
}

Require that a type argument has certain capabilities.

T Max<T>(T a, T b) where T : IComparable<T>
    => a.CompareTo(b) >= 0 ? a : b;

An interface can include an implementation that classes may override.

public interface ILogger
{
    void Log(string message);
    void Info(string message) => Log($"INFO: {message}");
}