C# - an example of creating an observable object with C# custom event

 public class ValueChangeData
 {
        public object oldValue;
        public object newValue;
 }
 public IObservable<ValueChangeData> CreateObservableSourceChange()
 {
     return Observable.Create<ValueChangeData>(
             observer =>
             {
                 DelegateValueChanged changedFunc = new DelegateValueChanged((oldValue, newValue) =>
                 {
                       ValueChangeData data = new ValueChangeData();
                       data.oldValue = oldValue;
                       data.newValue = newValue;
                       observer.OnNext(data);
                  });
                  OnValueChanged += changedFunc;
                  return () =>
                  {
                      OnValueChanged -= changedFunc;
                  };
              }
        );
   }