Thread-safe Silverlight Cairngorm

using System;
using System.Text;

namespace SilverlightCairngormDemo.Model
{
	public class FlickRPhoto
	{
		public string Id { get; set; }
		public string Owner { get; set; }
		public string Secret { get; set; }
		public string Server { get; set; }
		public string Farm { get; set; }
		public string Title { get; set; }
		public string ImageUrl
		{
			get
			{
				if (String.IsNullOrEmpty(Farm) || String.IsNullOrEmpty(Server) ||
					String.IsNullOrEmpty(Id) || String.IsNullOrEmpty(Secret))
					return null;
					
				return string.Format("http://farm{0}.static.flickr.com/{1}/{2}_{3}.jpg",
					Farm, Server, Id, Secret);
			}
		}
	}
}