I need your suggestion regarding loop in Model to ViewModel MVVM - loops

Question

I'am new to WPF and MVVM and I was given the task to continue working on one of the unfinished project that is made using the said technology. I've written a sample code below that is similar to the structure of the project.
My concern is, the loop used in GetBookPages() to display the details on the grid might take some time to finish.
public class BookModel
{
public string BookTitle { get; set; }
public List<BookDetailModel> BookDetails { get; set; }
}
public class BookDetailModel
{
public int Pages { get; set; }
public string Others { get; set; }
// ....
}
public class BookViewModel : INotifyPropertyChanged
{
private BookModel _model;
private ObservableCollection<BookDetailViewModel> _bookDetailSource;
private BookService _service;
public BookViewModel()
{
_model = new BookModel();
_service = new BookService();
GetBookPages();
}
/// <summary>
/// This is the item source of datagrid that is located in view
/// </summary>
public ObservableCollection<BookDetailViewModel> BookDetailSource
{
get { return _bookDetailSource; }
set
{
if (value == _bookDetailSource)
return;
_bookDetailSource = value;
OnPropertyChanged();
}
}
private void GetBookPages()
{
BookModel bookModel = _service.GetBookData();
var listOf = new List<BookDetailViewModel>();
bookModel.BookDetails.ForEach(e =>
{
// This is were the system's bottle neck is.
// can someone please suggests me a good work around.
listOf.Add(
new BookDetailViewModel
{
Others = e.Others,
// ....
});
});
BookDetailSource = new ObservableCollection<BookDetailViewModel>(listOf);
}
public string BookTitle
{
get { return _model.BookTitle; }
set
{
if (value == _model.BookTitle)
return;
_model.BookTitle = value;
OnPropertyChanged();
}
}
#region Property Change
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
public class BookDetailViewModel : INotifyPropertyChanged
{
private BookDetailModel _model;
#region Constructor
public BookDetailViewModel()
{
_model = new BookDetailModel();
ViewPageDataCommand = new RelayCommand(x => ViewPageData());
RemovePageCommdand = new RelayCommand(x => RemovePage());
}
#endregion
#region Properties
public int Page
{
get { return _model.Pages; }
set
{
if (value == _model.Pages)
return;
_model.Pages = value;
OnPropertyChanged();
}
}
public string Others
{
get { return _model.Others; }
set
{
if (value == _model.Others)
return;
_model.Others = value;
OnPropertyChanged();
}
}
#endregion
// These are the button command inside the grid's row
public ICommand ViewPageDataCommand { get; private set; }
public ICommand RemovePageCommdand { get; private set; }
private void ViewPageData()
{
// view the page data by clicking the row button inside the grid
}
private void RemovePage()
{
// will remove the currently selected row inside the grid
}
#region Property Change
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
public class BookService
{
public BookModel GetBookData()
{
var data = GetBookData(99);
data.BookDetails = GetBookDetail(99);
return data;
}
private BookModel GetBookData(int bookId)
{
// return 1 row only
}
private List<BookDetailModel> GetBookDetail(int bookId)
{
// return List<BookDetailModel> that might consists of more than 100 index's
}
}
I hope you understand what I mean. Your suggestion will be much appreciated. Thanks in advance!