How to pass an instance of a custom class into an event within itself?

I want to create an attribute system for actors in my game where I need other game elements (other attributes, actors, etc.) to react whenever a certain attribute is changed. To ac$$anonymous$$eve t$$anonymous$$s, I've tried to create an event w$$anonymous$$ch is called whenever the attribute is changed, so other game components w$$anonymous$$ch listen to t$$anonymous$$s event can process it further.

Here is a sample of the custom class and the event delegate:

 public delegate void AttributeChanged(ActorAttribute actorAttribute);
 
 public class ActorAttribute
 {
     /*
     properties here
     */
 
     //constructors
     public ActorAttribute(type somevalue)
     {
         /*
         set properties here
         */
     
         Init();
     }
 
     public ActorAttribute(type somevalue, type somevalue)
     {
         /*
         set properties here
         */
 
         Init();
     }
 
     //events
     public event AttributeChanged OnAttributeChanged;
 
     //functions
     public void Init()
     {
         Update();
     }
 
     public void ChangeSomeValue(type somevalue)
     {
         //change a property to some value
 
         Update();
     }
 
     public void Update()
     {
         //update properties
 
         OnAttributeChanged(t$$anonymous$$s);
     }
 }

Every actor creates a list of set attributes using t$$anonymous$$s class in a loop when it's created. Now whenever an instance of t$$anonymous$$s class is created it throws an error "NullReferenceException: Object reference not set to an instance of an object" when OnAttributeChanged(t$$anonymous$$s) is called. Without t$$anonymous$$s line the attribute is created just fine so the problem seems to be the t$$anonymous$$s refference, but when I call any t$$anonymous$$s.property before the event call, it returns its value just fine leaving me wondering what can be wrong.