DictionaryExtensions

        /// <summary>
        /// 从字典中获取值，不存在则返回字典<typeparamref name="TValue"/>类型的默认值
        /// </summary>
        /// <typeparam name="TKey">字典键类型</typeparam>
        /// <typeparam name="TValue">字典值类型</typeparam>
        /// <param name="dictionary">要操作的字典</param>
        /// <param name="key">指定键名</param>
        /// <returns>获取到的值</returns>
        public static TValue GetOrDefault<TKey, TValue>(this IDictionary<TKey, TValue>dictionary, TKey key)
        
        /// <summary>
        /// 获取指定键的值，不存在则按指定委托添加值
        /// </summary>
        /// <typeparam name="TKey">字典键类型</typeparam>
        /// <typeparam name="TValue">字典值类型</typeparam>
        /// <param name="dictionary">要操作的字典</param>
        /// <param name="key">指定键名</param>
        /// <param name="addFunc">添加值的委托</param>
        /// <returns>获取到的值</returns>
        public static TValue GetOrAdd<TKey, TValue>(this IDictionary<TKey, TValue>dictionary, TKey key, Func<TValue> addFunc)