负载均衡环境下，Web应用的缓存管理

p;       return cmd;
        }

        private void UpdateCacheDependency(string key)
        {
            SqlCommand cmd = this.GetUpdateCommand(key);
            using (cmd.Connection)
            {
                cmd.Connection.Open();
                cmd.Prepare();
                cmd.ExecuteNonQuery();
            }
        }

        protected override void OnBeforeAdd(string key)
        {
            this.UpdateCacheDependency(key);
        }

        protected override CacheDependency GetCacheDependency(string key)
        {
            SqlCommand cmd = this.GetSelectCommand(key);
            SqlCacheDependency sqlCacheDependency = new SqlCacheDependency(cmd);
            using (cmd.Connection)
            {
                cmd.Connection.Open();
                cmd.Prepare();
                cmd.ExecuteNonQuery();
            }
            return sqlCacheDependency;
        }

        public SqlDependencyWebCache(string connectionString)
        {
            this._connectionString = connectionString;
        }

        public override void Remove(strin