C#

public class BusinessObjectBase
{
}

public class BusinessObjectList<T> : List<T> where T : BusinessObjectBase
{}

public class BusinessObjectDataSet : DataSet
{
    protected BusinessObjectList<BusinessObjectBase>[] _BusinessObjectListArray = null;

    public virtual void AddBusinessObjectList(BusinessObjectList<BusinessObjectBase> List)
    {

    }


}

private class MyBusinessObject : BusinessObjectBase
{
    public MyBusinessObject()
    {

    }
}

private class MyBusinessObjectList<MyBusinessObject> : BusinessObjectList<T> where T : BusinessObjectBase
{

}


 BusinessObjectDataSet Set = new BusinessObjectDataSet();

 MyBusinessObject Bo = new MyBusinessObject();                                                 // Derives from BusinessObjectBase

 MyBusinessObjectList<MyBusinessObject> BoList = new MyBusinessObjectList<MyBusinessObject>(); // Derives from BusinessObjectList<T>

 Set.AddBusinessObjectList(BoList);  // Here it says "Error CS1503  Argument 1: cannot convert from 'MyBusinessObjectList<MyBusinessObject>' to 'BusinessObjectList<BusinessObjectBase>'

using Microsoft.WindowsAPICodePack.Taskbar;
private TabbedThumbnail customThumbnail;
protected override void OnShown(EventArgs e)
		{
			base.OnShown(e);

			customThumbnail = new TabbedThumbnail(this.Handle, this.Handle);
			TaskbarManager.Instance.TabbedThumbnail.AddThumbnailPreview(customThumbnail);
			customThumbnail.TabbedThumbnailBitmapRequested += customThumbnail_TabbedThumbnailBitmapRequested;
        }

		private Bitmap GenerateBitmap()
		{
			Bitmap bitmap = new Bitmap(150, 150);

			using (var g = Graphics.FromImage(bitmap))
			{
                g.DrawImage(Properties.Resources.tx, new Rectangle(0,0,150,150));
			}

			return bitmap;
		}
		void customThumbnail_TabbedThumbnailBitmapRequested(object sender, TabbedThumbnailBitmapRequestedEventArgs e)
		{
			var bitmap = GenerateBitmap();
			customThumbnail.SetImage(bitmap);

			ThreadPool.QueueUserWorkItem(c =>
			                             	{
			                             		Thread.Sleep(2000);
			                             		this.Invoke(new MethodInvoker(InvalidateThumbnail));
			                             	});
		}
		private void InvalidateThumbnail()
		{
			customThumbnail.InvalidatePreview();
		}