public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback)
 {
     return false;
 }

 public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback)
 {
     _expireCallBack = expireCallback;
     return true;
 }

 /// <summary>
 /// This method sets the reference for the ExpireCallback delegate if setting is enabled.
 /// </summary>
 /// <param name="expireCallback"></param>
 /// <returns>false </returns>
 public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback)
 {
   if (this.enableExpireCallback)
   {
     this.expireCallback = expireCallback;
     return true;
   }
   return false;
 }

 // Called by SessionStateModule to notify the provider that Session_End is defined
 // in global.asax, and so when an item expires, it should call the expireCallback
 // If the provider does not support session expiry, it should return false.
 public abstract bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback);

        /// <summary>
        /// SessionStateProviderBase.SetItemExpireCallback
        /// </summary>
        public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback)
        {
            // Accept and store callback if session expire callback is enabled. If not, return false in order to inform SessionStateModule
            // the session expire callback is not supported.
            if (!m_enableExpireCallback)
                return false;

            m_expireCallback = expireCallback;
            return true;
        }

		public override bool SetItemExpireCallback (SessionStateItemExpireCallback expireCallback) {
			return true; //we call session.invalidate so our session listener will call Session_OnEnd
		}

 public abstract virtual bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback)
 {
 }

 public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback)
 {
     throw new NotImplementedException();
 }

    } // End of the CreateNewStoreData method

    #endregion

    #region Update methods

    /// <summary>
    /// Set the callback for session expiration
    /// </summary>
    public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback)
    {
        return false;

    } // End of the SetItemExpireCallback method

		/// <summary>
		/// Sets a reference to the <see cref="T:System.Web.SessionState.SessionStateItemExpireCallback"></see> delegate for the Session_OnEnd event defined in the Global.asax file.
		/// </summary>
		/// <param name="expireCallback">The <see cref="T:System.Web.SessionState.SessionStateItemExpireCallback"></see>  delegate for the Session_OnEnd event defined in the Global.asax file.</param>
		/// <returns>
		/// true if the session-state store provider supports calling the Session_OnEnd event; otherwise, false.
		/// </returns>
		public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback)
		{
			throw new Exception("The method or operation is not implemented.");
		}