Display for selection multiple document (as in files) thumbnails

private void loadImagesIntoListToolStripMenuItem_Click(object sender, EventArgs e)
{
    var browserDlg = new FolderBrowserDialog();
    if (browserDlg.ShowDialog() == System.Windows.Forms.DialogResult.OK)
    {
        var filePaths = System.IO.Directory.GetFiles(browserDlg.SelectedPath, "*.pdf");
        _rasterImageList.BeginUpdate();
        var count = 1;
        foreach (var file in filePaths)
        {
            using (var thumbnailImage = _codecs.Load(file,1))
            {
                var item = new ImageViewerItem();
                item.Image = thumbnailImage.Clone();
                item.PageNumber = count;
                item.Text = "Page " + item.PageNumber.ToString();  
                _rasterImageList.Items.Add(item);
                count++;
            }
        }
        _rasterImageList.EndUpdate();
    }
}

var imageViewer;
var thumbnailViewer;

window.onload = function () {
	InitImageViewer();
	InitThumbnailViewer();
};

function InitThumbnailViewer()
{
	var thumbnailViewerDiv = document.getElementById("thumbnailViewerDiv");
	var createOptions = new lt.Controls.ImageViewerCreateOptions(thumbnailViewerDiv);
	createOptions.viewLayout = new lt.Controls.ImageViewerVerticalViewLayout();
    thumbnailViewer = new lt.Controls.ImageViewer(createOptions);
	thumbnailViewer.imageBorderThickness = 1;
	thumbnailViewer.itemBackgroundColor = "yellow";
	thumbnailViewer.itemBorderThickness = 1;
	
	thumbnailViewer.itemSize = lt.LeadSizeD.create(150, 150);
	thumbnailViewer.itemSizeMode = lt.Controls.ControlSizeMode.fit;
	
	thumbnailViewer.items.addFromUrl("Images/Page1.png", lt.LeadSizeD.empty);
	thumbnailViewer.items.addFromUrl("Images/Page2.png", lt.LeadSizeD.empty);
	thumbnailViewer.items.addFromUrl("Images/Page3.png", lt.LeadSizeD.empty);
	thumbnailViewer.items.addFromUrl("Images/Page4.png", lt.LeadSizeD.empty);	 
	
	thumbnailViewer.interactiveModes.beginUpdate();
	var interactiveMode = new lt.Controls.ImageViewerSelectItemsInteractiveMode();
	interactiveMode.isEnabled = true;
	thumbnailViewer.interactiveModes.add(interactiveMode);
	thumbnailViewer.interactiveModes.endUpdate();

	thumbnailViewer.selectedItemBackgroundColor = "lightblue";
	
	thumbnailViewer.selectedItemsChanged.add(function(sender,e){
		imageViewer.imageUrl = this.items.getSelected()[0].url;
	});
}

function InitImageViewer()
{
	var imageViewerDiv = document.getElementById("imageViewerDiv");
    var createOptions = new lt.Controls.ImageViewerCreateOptions(imageViewerDiv);
    imageViewer = new lt.Controls.ImageViewer(createOptions);
    // Load an image in the viewer
    imageViewer.imageUrl = "Images/Page1.png";
}