ItemsControl that loads items one by one asynchronously.

Question

Hey Guys,

I am creating a custom DataGrid by deriving the traditional tookit based WPF DataGrid. I want a functionality in the grid to load items one by one asynchronously, wherein as soon as ItemsSource is changed i.e. a new collection is Set to the ItemsSource property or the bound collection is Changed dues to items that rae added, moved or removed (wherein the notifications comes to the data grid when the underlying source implements INotifyCollectionChanged such as ObservableCollection).

This is because even with virtualising stackpanel underneath the datagrid takes time to load (2-3 seconds delay) to load the data rows when it has several columns and some are template based. With above behavior that delay would "appear" to have reduced giving datagrid a feel that it has the data and is responsive enough to load it.

How can I achieve it?

Thx Vinit.

Answer 1

Sounds like you are looking for data virtualization', which typically means creating your own custom type that resembles IList, and doing a lot of work to hydrate objects after-the-fact.

You will end up having your data that the grid is displaying look something like this:

Index 0: new MyDataObject(0);
Index 1: new MyDataObject(1);

And MyDataObject implements INotifyPropertyChanged.

In the constructor, you do the logic necessary to time, schedule, or interpret when the real results should be read. Until then, you return rather empty data... null and string.Empty from your properties.

Then, once the data becomes available (ideally in a background thread, read from wherever - your own local data, or a database or web service), then you can update the real underlying property values and fire the property change notifications so that the UI gets properly loaded then.

It's a little too complex to just jump into, so some searching will help. Hope this gets you started.