c# - Why is WPF not updating on INotifyPropertyChanged? -

i implementing inotifypropertychanged implementing same interfaces , passing calls observablecollection`1:

class wrappedobservablecollection<telement> : inotifypropertychanged, inotifycollectionchanged //, ...others {     private readonly observablecollection<telement> baselist;      public wrappedobservablecollection(observablecollection<telement> baselist)     {         contract.requires(baselist != null);          this.baselist = baselist;     }      #region wrapping of baselist      public event propertychangedeventhandler propertychanged     {         add { ((inotifypropertychanged)baselist).propertychanged += value; }         remove { ((inotifypropertychanged)baselist).propertychanged -= value; }     }      #endregion } 

this works fine, when bind .count property, ui never updates. suspect wrong implementation of inotifypropertychanged have verified propertychanged.add called, , event raised when property being changed.

passing .add call internal list insufficient wpf uses sender parameter of event determine bindings need updated. use following wrap inotifypropertychanged while updating sender:

class wrappedobservablecollection<telement> : inotifypropertychanged, inotifycollectionchanged //, ...others {     private readonly observablecollection<telement> baselist;      public wrappedobservablecollection(observablecollection<telement> baselist)     {         contract.requires(baselist != null);          this.baselist = baselist;         ((inotifypropertychanged)this.baselist).propertychanged += (sender, e) => propertychanged?.invoke(this, e);     }      #region wrapping of baselist      public event propertychangedeventhandler propertychanged;      #endregion }