this.virtualGrid.FilterColumn(2);

var virtualizingCanvasBase = this.virtualGrid.ChildrenOfType<VirtualizingCanvasBase>().FirstOrDefault();

var columnsRenderInfoInfo = virtualizingCanvasBase.GetType().GetProperty("ColumnsRenderInfo", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);

var columnsRenderInfo = columnsRenderInfoInfo.GetValue(virtualizingCanvasBase);

var offsetMethodInfo = columnsRenderInfo.GetType().GetMethod("OffsetFromIndex");

var filteringPopupPropertyInfo = this.virtualGrid.GetType().GetProperty("FilteringPopup", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);

Popup filteringPopup = (Popup)filteringPopupPropertyInfo.GetValue(this.virtualGrid);

filteringPopup.HorizontalOffset = (double)offsetMethodInfo.Invoke(columnsRenderInfo, new object[1] { 2 });

// SomeVirtualGrid.xaml.cs
public SomeVirtualGrid()
{
    InitializeComponent();
    vg.PinColumnLeft(0);
    vg.PinColumnLeft(1);
    vg.PinColumnLeft(2);
}

static MainWindow()
{   
	CommandManager.RegisterClassCommandBinding(typeof(RadVirtualGrid), new CommandBinding(RadVirtualGridCommands.Copy, OnVirtualGridCopyExecuted, OnVirtualGridCopyCanExecute));
}

private static void OnVirtualGridCopyCanExecute(object sender, CanExecuteRoutedEventArgs e)
{
	e.Handled = true;
	e.CanExecute = true;
}

private static void OnVirtualGridCopyExecuted(object sender, ExecutedRoutedEventArgs e)
{
	var virtualGrid = (RadVirtualGrid)sender;
	var strBuilder = new StringBuilder();
	// DataView is a custom property in MyDataProvider (deriving from DataProvider) and it just returns this.Source (which is a protected property).
	var items = ((MyDataProvider)virtualGrid.DataProvider).DataView; 
	int pinnedColumnsCount = (int)virtualGrid.Tag;
	
	foreach (VirtualGridCellInfo cell in virtualGrid.SelectedCells)
	{
		int columnIndex = cell.ColumnIndex + pinnedColumnsCount;
		ItemPropertyInfo propertyInfo = virtualGrid.DataProvider.ItemProperties[columnIndex];
		var descriptor = (PropertyDescriptor)propertyInfo.Descriptor;
		object rowData = items.GetItemAt(cell.RowIndex);
		object cellValue = descriptor.GetValue(rowData);

		strBuilder.Append(cellValue + " ");
	}

	Clipboard.SetText(strBuilder.ToString());
}

private void VirtualGrid_PreviewKeyDown(object sender, System.Windows.Input.KeyEventArgs e)
{
	var virtualGrid = (RadVirtualGrid)sender;
	if (e.Key == System.Windows.Input.Key.Right)
	{
		var currentCell = virtualGrid.CurrentCellInfo;
		var newCellIndex = Math.Min(currentCell.ColumnIndex + 1, virtualGrid.InitialColumnCount - 1);
		var nextCell = new VirtualGridCellInfo(currentCell.RowIndex, newCellIndex, vg);
		virtualGrid.CurrentCellInfo = nextCell;
		virtualGrid.SelectedCells.Clear();                
		virtualGrid.SelectedCells.Add(nextCell);

		var viewportWidth = this.panel.ViewportWidth - virtualGrid.RowHeaderWidth;
		var newCellX = (virtualGrid.ColumnWidth * nextCell.ColumnIndex) - this.panel.HorizontalOffset;
		if (newCellX >= viewportWidth)
		{
			var delta = virtualGrid.ColumnWidth + (newCellX - viewportWidth);
			this.panel.SetHorizontalOffset(this.panel.HorizontalOffset + delta);
		}
		e.Handled = true;
	}
}

private VirtualGridCompoundPanel panel;

private void VirtualGrid_Loaded(object sender, RoutedEventArgs e)
{
	var virtualGrid = (RadVirtualGrid)sender;
	this.panel = virtualGrid.FindChildByType<VirtualGridCompoundPanel>();            
}