c# - DynamicObject behaves differently for null values -

here dynamicdataobject class derived dynamicobject

 public class dynamicdataobject : dynamicobject  {         private readonly dictionary<string, object> _datadictionary = new dictionary<string, object>();          public override bool trygetmember(getmemberbinder binder, out object result)         {             return _datadictionary.trygetvalue(binder.name, out result);         }          public override bool trysetmember(setmemberbinder binder, object value)         {             if (!_datadictionary.containskey(binder.name))             {                 _datadictionary.add(binder.name, value);                 return true;             }              return false;         }          public override ienumerable<string> getdynamicmembernames()         {             return _datadictionary.keys;         }   } 

and consuming dynamicdataobject below.

 public mainwindow()  {      initializecomponent();      dynamic person = new dynamicdataobject();      person.firstname = "vimal";      person.lastname = "adams";      person.address = null;  } 

i can see members of person , it's values in _datadictionary @ same time debugger view excludes members having null value. person.address member not visible in dynamic view collection.(please see below screenshot). can please me understanding why dynamicobjectbehaves differently in scenario?

i think optimization. there no use in keeping reference default value of type. returns default(t) when try access it.

it behaves dictionary:

string property = "address"; object val;  if (!dic.trygetvalue(property, out val)) {     return default(t); } else {     return (t)val; // simplification } 

what point here keep address in dictionary? none. why removed.