Demonstrates callbacks inside events using Action<T> or Func<T>

CallbacksInEvents.cs

public delegate void CreateThingHandler(Func<Thing, Thing> preCreate, Thing thing);

public class Thing
{
  public static event CreateThingHandler OnMadeThing;
  public bool Valid { get; set;}
  List<Thing> things = new List<thing>();

  public static Thing MakeThing(Func<Thing, Thing> func)
  {
    var thing = new Thing();
    thing = OnMadeThing(func, thing);
    things.Add(thing);
    return thing;
  }
}


//// Usage

void ValidateThing(Func<Thing, Thing> func, Thing thing)
{
  return func(thing);
}
Thing.OnMadeThing += ValidateThing;

thing = Thing.MakeThing(t => t.Valid = true);
thing.Valid // true