// This gets called once when we register, but shouldn't get called again
 // except build case. in build case, VS will refresh all errors at the end of build
 public virtual int EnumTaskItems(out IVsEnumTaskItems ppenum)
 {
     ppenum = new EmptyVsEnumTaskItems();
     return(VSConstants.S_OK);
 }
 // This gets called once when we register, but shouldn't get called again 
 // except build case. in build case, VS will refresh all errors at the end of build
 public virtual int EnumTaskItems(out IVsEnumTaskItems ppenum)
 {
     ppenum = new EmptyVsEnumTaskItems();
     return VSConstants.S_OK;
 }