Custom Unity lifetime manager

SessionLifetimeManager.cs

public class SessionLifetimeManager<T> : Microsoft.Practices.Unity.LifetimeManager
    {
        private string key;

        public SessionLifetimeManager()
        {
            this.key = typeof(T).Name;
        }

        /// <summary>
        /// Retrieve a value from the backing store associated with this Lifetime policy.
        /// </summary>
        /// <returns>
        /// the object desired, or null if no such object is currently stored.
        /// </returns>
        public override object GetValue()
        {
            return HttpContext.Current.Session[this.key];
        }

        /// <summary>
        /// Stores the given value into backing store for retrieval later.
        /// </summary>
        /// <param name="newValue">The object being stored.</param>
        public override void SetValue(object newValue)
        {
            HttpContext.Current.Session[this.key] = newValue;
        }

        /// <summary>
        /// Remove the given object from backing store.
        /// </summary>
        public override void RemoveValue()
        {
        }
    }

SimpleSessionStore.cs

public interface ISession{
  string Get(string key);
  void Set(string key, string value);
}

public class SimpleSessionStore : ISession{
  public string Get(string key){
    return HttpContext.Current.Session[key];
  }
  
  public void Set(string key, string value){
    HttpContext.Current.Session[key] = value;
  } 
}