internal void RegisterTiledTexture(String key, TiledTexture texture, TextureCachePolicy cachePolicy)
{
if(String.IsNullOrWhiteSpace(key))
throw new ArgumentNullException();
if(texture == null)
throw new ArgumentNullException();
if(TiledTextures.ContainsKey(key))
throw new ArgumentException("Attempt to register duplicate key.");
TiledTextures.Add(key, texture);
CachePolicies.Add(key, cachePolicy);
Users.Add(key, new List<DrawableBase>());
}