c# - wp7 and dependency property : onChanged and onRead? -

well want build wp7 control,so write , go well, problem can intercept on write(see onitemssourcepropertychanged)but not on read explain better:

public static readonly dependencyproperty itemssourceproperty=          dependencyproperty.register(              "itemssource",              typeof(observablecollection<objwithdesc>),              typeof(horizontallistbox),              new propertymetadata(onitemssourcepropertychanged)          );         static void onitemssourcepropertychanged(dependencyobject obj,dependencypropertychangedeventargs e) {          ((horizontallistbox) obj).onitemssourcepropertychanged(e); } 

onitemssourcepropertychanged called when use setvalue(dp,..) there isn't onitemssourcepropertyread ? called when use getvalue()? thanks

you add onread action getter of backing field:

    public string itemssource     {                  {              // call onread functionality here!             return (string)getvalue(itemssourceproperty);          }          set          {              setvalue(itemssourceproperty, value);         }     }