Binding a DataGrid to a large IList dataset

Question

I'm trying to use System.Windows.Controls.GridView (specifically, it is wrapped by Eto.Forms.GridView) to display a large dataset (1m+ rows) and finding it is unusable.

From what I can see, when the GridView.ItemsSource property is set, the grid immediately calls GetEnumerator() and therefore causes a large lag before it can display the enumerated dataset. As such, I have implemented a workaround to quickly display the grid using the code shown below.

Basically what the code attempts to do is override the usual List.GetEnumerator() functionality and initially give a small chunk of rows from the underlying list. After that, it utilizes the INotifyCollectionChanged.CollectionChanged event to add the remaining rows, chunks at a time.

While the solution works as far as displaying the grid relatively quickly on the initial load, there are a number of problems including:

• As the list is populated via the thread, it becomes very unresponsive and of course the aesthetics of seeing the scroll-bar extending doesn't look great and;
• The biggest of issue is that the grid becomes entirely unresponsive for a minute (+) each time you attempt to scroll down.

Does anyone know how I can make a DataGrid work with a large IList datasource? For the record, I cannot change controls as I am using ETO.Forms for cross-platform desktop UI capability.

Thanks.

// The underlying IList containing a large list of rows
IList<T> _underlyingList;

public IEnumerator<T> GetEnumerator() {
  // Create an initial chunk of data to immediately return to the grid for display
  long i = 0;
  for (i = 0; i < _underlyingList.Count; i++) {
    yield
    return _underlyingList[i];
    if (i > 100) break;
  }

  // Record the UI context so we can update the collection in that thread
  var uiContext = SynchronizationContext.Current;

  // Now we create a task that will populate the rest of the grid by
  // raising "CollectionChanged" events to add the remaining rows.
  Task.Run(() => {
    // Create a temporary list to add to
    var list = new List <T> ();

    // Add to our list
    for (long x = i; x < _underlyingList.Count; x++) {
      list.Add(_underlyingList[x]);

      // Every x items, fire a "CollectionChanged" event.
      if (x % 1000 == 0) {
        var e = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, list);

        // Invoke the CollectionChanged event on the UI thread
        uiContext.Send(p => CollectionChanged?.Invoke(this, e), null);

        list.Clear();
      }
    }

    // Fire any last event as required.
    if (list.Count > 0) {
      var e = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, list);
      CollectionChanged?.Invoke(this, e);
      uiContext.Send(p => CollectionChanged?.Invoke(this, e), null);
    }
  });
}```