updated PageParameterData

PageParameterData.cs

public class PageParameterData<TVm> : AbstractNotifyPropertyChanged
    {
        private int _currentPage;
        private int _pageCount;
        private int _pageSize;
        private int _totalSize;
        private int _startingIndex;
        private int _endingIndex;
        private readonly Command _cmdPageForward;
        private readonly Command _cmdPageToEnd;
        private readonly Command _cmdPageBackward;
        private readonly Command _cmdPageToStart;

        private readonly IObservableCollection<TVm> _masterList;
        private readonly IObservableCollection<TVm> _filteredList;

        public PageParameterData(int currentPage, int pageSize, IObservableCollection<TVm> filteredList, IObservableCollection<TVm> masterList)
        {
            _masterList = masterList;
            _filteredList = filteredList;
            _currentPage = currentPage;
            _pageSize = pageSize;
            _totalSize = masterList.Count;

            _masterList.CollectionChanged += _masterList_CollectionChanged;
            _filteredList.CollectionChanged += _filteredList_CollectionChanged;

            _cmdPageForward = new Command(() => CurrentPage = CurrentPage + 1, () => CurrentPage < PageCount);
            _cmdPageBackward = new Command(() => CurrentPage = CurrentPage - 1, () => CurrentPage > 1);
            _cmdPageToEnd = new Command(() => CurrentPage = PageCount, () => CurrentPage < PageCount);
            _cmdPageToStart = new Command(() => CurrentPage = 1, () => CurrentPage > 1);
        }

        void _filteredList_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {
            StartingIndex = ((CurrentPage - 1) * PageSize) + 1;

            if (_filteredList.Count == 0)
                StartingIndex = EndingIndex = 0;
            else if (_currentPage == _pageCount && StartingIndex > 0)
                EndingIndex = StartingIndex + (_filteredList.Count - 1);
            else
                EndingIndex = _currentPage*_pageSize;
        }

        void _masterList_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {
            if (CurrentPage == PageCount)
                EndingIndex = _masterList.Count;
        }

        public void Update(IPageResponse response)
        {
            CurrentPage = response.Page;
            PageSize = response.PageSize;
            PageCount = response.Pages;

            if (response.TotalSize != 0)
                TotalSize = response.TotalSize;

            _cmdPageForward.Refresh();
            _cmdPageBackward.Refresh();
            _cmdPageToEnd.Refresh();
            _cmdPageToStart.Refresh();
        }

        public ICommand CmdPageForward
        {
            get { return _cmdPageForward; }
        }

        public ICommand CmdPageBackward
        {
            get { return _cmdPageBackward; }
        }

        public ICommand CmdPageToEnd
        {
            get { return _cmdPageToEnd; }
        }

        public ICommand CmdPageToStart
        {
            get { return _cmdPageToStart; }
        }

        public int TotalSize
        {
            get { return _totalSize; }
            private set { SetAndRaise(ref _totalSize, value); }
        }

        public int PageCount
        {
            get { return _pageCount; }
            private set { SetAndRaise(ref _pageCount, value); }
        }

        public int CurrentPage
        {
            get { return _currentPage; }
            private set { SetAndRaise(ref _currentPage, value); }
        }

        public int PageSize
        {
            get { return _pageSize; }
            private set { SetAndRaise(ref _pageSize, value); }
        }

        public int StartingIndex
        {
            get { return _startingIndex; }
            private set { SetAndRaise(ref _startingIndex, value); }
        }

        public int EndingIndex
        {
            get { return _endingIndex; }
            private set { SetAndRaise(ref _endingIndex, value); }
        }
    }