C#

Magic Methods Curiosity

The C# language includes a number of duck-typed “Magic Methods”. Unusually (for C#), these methods are special because of their name, not because of the interface they’re on!

`.GetAwaiter`

GetAwaiter() lets you define what happens when a value is awaited.

class Program
{
    static async Task Main(string[] args)
    {
        await 10000; // Delays execution by 10,000ms
    }
}

public static class IntExtensions
{
    public static TaskAwaiter GetAwaiter(this int i)
    {
        return Task.Delay(i).GetAwaiter();
    }
}

`.Add`

.Add<T> lets you define how to include a value in a collection when using the collection initializer syntax.

In this example, we’ll teach C# to let you include one list inside another, by flattening the inner list:

 class Program
{
    static void Main(string[] args)
    {
        var list1 = new List<string> {"two", "three", "four"};
        var list2 = new List<string> {"one", list1, "five"};

        // list2 is "one, two, three, four, five"
    }
}

public static class ListExtensions
{
    // Tell C# that we know how to include an IEnumerable in a list
    public static void Add<T>(this List<T> list, IEnumerable<T> things)
    {
        foreach (var thing in things)
        {
            list.Add(thing);
        }
    }
}

C# Garbage Collector implementation Curiosity

The C# garbage collector is implemented as a single 1.8 MB, 52,000 line C++ file.

https://raw.githubusercontent.com/dotnet/runtime/main/src/coreclr/gc/gc.cpp