public static PropertyChangedEventHandler MakeWeak(this PropertyChangedEventHandler handler, Action <PropertyChangedEventHandler> unregister)
{
Validate(handler, unregister);
var method_type = handler.Method.DeclaringType ?? throw new Exception($"method handler declaring type is null");
var weh_type = typeof(WeakPropChangedHandlerImpl <>).MakeGenericType(method_type);
var cons = weh_type.GetConstructor(new[] { handler.GetType(), unregister.GetType() }) ?? throw new Exception($"weak event handler constructor not found");
var weh = (IWeakPropChangedHandler)cons.Invoke(new object[] { handler, unregister });
return(weh.Handler);
}
