public class Celebrity
{
    public string? Name { get; set; }
    public int Age { get; set; }

    public override string ToString() => $"{Name}: {Age}";

    public void Test()
    {
        var celebrity = new Celebrity { Name = "Jennifer Aniston", Age = 54 };
        ChangeCelebrity(celebrity);

        Console.WriteLine(celebrity);
    }

    static void ChangeCelebrity(Celebrity celebrity)
    {
        celebrity.Name = "Brad Pitt";
        celebrity.Age = 60;

        celebrity = new Celebrity { Name = "Angelina Jolie", Age = 48 };
    }
}

public record struct Celebrity2(string Name)
{
    public override string ToString() => Name;

    public void Test()
    {
        var celebrity = new Celebrity2("Jennifer Aniston");
        ChangeCelebrity(celebrity);

        Console.WriteLine(celebrity);
    }

    static void ChangeCelebrity(Celebrity2 celebrity)
    {
        celebrity.Name = "Brad Pitt";
        celebrity = new Celebrity2("Angelina Jolie");
    }
}

public async Task Test()
{
    try
    {
        await Task.Factory.StartNew<int>(() => throw new Exception())
            .ContinueWith(x => 2 * 2)
            .ContinueWith(x => Math.Sqrt(x.Result))
            .ContinueWith(x => Console.WriteLine(x.Result));
    }
    catch (AggregateException)
    {
        Console.WriteLine(nameof(AggregateException));
    }
    catch (Exception)
    {
        Console.WriteLine(nameof(Exception));
    }
}

abstract class A
{
    public abstract string GetName();
}

class B : A
{
    public override string GetName() => nameof(B);
}

class C : B
{
    public new string GetName() => nameof(C);
}

public void Test()
{
    A b = new B();
    A c = new C();
    Console.WriteLine(b.GetName() + c.GetName());
}

private object _lock = new();
private int _counter;

public async Task Test()
{
    Task.WhenAll(
        Increment(),
        Increment(),
        Increment());

    Console.WriteLine(_counter);
}

async Task Increment()
{
    lock (_lock)
    {
        await Task.Delay(1000);
        _counter++;
    }
}

public void Test()
{
    try
    {
        using (null)
        {
            Console.Write("I'm in");
            return;
        }

        Console.Write("I'm out");
    }
    catch (Exception)
    {
        Console.Write(nameof(Exception));
    }
}