C# Quick Reference

Console.WriteLine("Hello");

int count = 10;

var name = "Ada";

const int Max = 100;

int? age = null;

string? nickname = null;

string? line = Console.ReadLine();

int.Parse("42")

int.TryParse(text, out var n)

42.ToString()

name ?? "guest"

user?.Address?.City

$"Hi {name}, you are {age}"

$"{price:C}", $"{ratio:P1}", $"{n:N0}"

s.ToUpper()

s.Trim()

s.Contains("x")

s.Replace("a", "b")

s.Split(',')

string.Join(", ", names)

var json = """
    { "name": "Ada" }
    """;

var nums = new List<int> { 3, 1, 2 };

nums.Add(4);

nums.Remove(1);

var ages = new Dictionary<string, int> { ["Ada"] = 36 };
ages.TryGetValue("Bob", out var age);

int[] scores = [90, 85, 77];

var names = users.Where(u => u.Age > 18).Select(u => u.Name).ToList();

users.OrderBy(u => u.Name)

OrderByDescending(u => u.Age)

nums.Reverse();

nums.AsEnumerable().Reverse()

nums.Sum()

nums.Average()

nums.Max()

users.FirstOrDefault(u => u.Id == 7)

users.Any(u => u.IsAdmin)

users.GroupBy(u => u.Role)

if (x > 0) { } else if (x == 0) { } else { }

var label = n switch
{
    0 => "zero",
    > 0 => "positive",
    _ => "negative",
};

for (var i = 0; i < 5; i++) { }

foreach (var item in items) { }

while (running) { }

if (shape is Circle { Radius: > 10 } c) { }

public class User
{
    public required string Name { get; init; }
    public int Age { get; set; }
}

public class Dog(string name)
{
    public string Bark() => $"{name}: Woof";
}

public record Point(int X, int Y);

public interface IShape { double Area(); }

public class Puppy : Dog { }

public enum Status { Active, Disabled }

public async Task<string> LoadAsync()
{
    using var http = new HttpClient();
    return await http.GetStringAsync(url);
}

await Task.WhenAll(LoadA(), LoadB());

try
{
    Risky();
}
catch (InvalidOperationException ex)
{
    Console.WriteLine(ex.Message);
}
finally
{
    Cleanup();
}

File.ReadAllText("in.txt")

File.WriteAllText("out.txt", text)

dotnet new console -n MyApp

dotnet run

dotnet build

dotnet test

dotnet add package Newtonsoft.Json

dotnet publish -c Release