I’ve made small demo how to create easily endless scrolling of almost 2 mil. records (exact count is 1770607) using RadGridView for WPF.

When you reach the bottom of the vertical scrollbar, more data will be retrieved on-the-fly from the data-base server:

For asynchronous data loading you can use BackgroundWorker:

BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
worker.RunWorkerAsync();

…

void worker_DoWork(object sender, DoWorkEventArgs e)
{ 
    NorthwindDataContext context = new NorthwindDataContext();
    queryable = from o in context.Orders
                from od in context.Order_Details
                       select new
                       {
                           od.OrderID,
                           od.ProductID,
                           od.UnitPrice,
                           od.Quantity,
                           od.Discount,
                           o.CustomerID,
                           o.EmployeeID,
                           o.OrderDate
                       };

}

and on GridViewScrollViewer VerticalScrollEnded event you can get more records:

void ScrollOwner_VerticalScrollEnded(object sender, System.Windows.Controls.Primitives.ScrollEventArgs e)
{
    if (((ScrollBar)e.OriginalSource).Maximum == e.NewValue)
    {
        pageSize = pageSize + 50;
        worker.RunWorkerAsync();
    }
}

In this demo you can find also how to cancel the default grid sorting and perform your own sorting and how to make nice loading image for your asynchronous operations.

Enjoy!

[Download]