Playground

import System;
import System.Reflection;

public attribute Column
{
	public:
		str Name;
		i32 Width;
		bool Required;

		new(str name) { Name = name; }
}

public attribute Note : Column
{
	public:
		new() : base("note") { }
}

[Column("people", Width = 40)]
public class Person
{
	public:
		[Column("full name", Required = true)] str Name = "";
		[Note] i32 Age;

		[Column("greet")]
		Greet([Column("who")] str other) : str => "hi " + other;
}

Main()
{
	Type t = typeof(Person);
	loop (any a in t.GetCustomAttributes())
	{
		if (a is ColumnAttribute c)
			Console.WriteLine("type: " + c.Name + " " + c.Width);
	}
	FieldInfo? name = t.GetField("Name");
	if (name is FieldInfo f && f.GetCustomAttributes(typeof(ColumnAttribute))[0] is ColumnAttribute col)
		Console.WriteLine("field: " + col.Name + " " + col.Required);
	if (t.GetField("Age") is FieldInfo age)
		Console.WriteLine("Age has Note: " + age.IsDefined(typeof(NoteAttribute)));
	MethodInfo? greet = t.GetMethod("Greet");
	if (greet is MethodInfo m)
	{
		ParameterInfo p = m.GetParameters()[0];
		if (p.GetCustomAttributes()[0] is ColumnAttribute pc)
			Console.WriteLine("parameter: " + pc.Name);
	}
	Console.WriteLine(t.IsDefined(typeof(NoteAttribute)));
}