C#实现简单的顺序栈

顺序栈：
1.接口类：

 interface IStackDS<T>
    {
   
        /// <summary>
        /// 获取元素个数
        /// </summary>
        int Count {
    get; }
        /// <summary>
        /// 获取栈中元素个数
        /// </summary>
        /// <returns></returns>
        int GetLength();
        /// <summary>
        /// 栈是否为空
        /// </summary>
        /// <returns></returns>
        bool IsEmpty();
        /// <summary>
        /// 清空栈
        /// </summary>
        void Clear();
        /// <summary>
        /// 入栈
        /// </summary>
        /// <param name="item">需要入栈的元素</param>
        void Push(T item);
        /// <summary>
        /// 向栈中添加一个元素
        /// </summary>
        /// <param name="item"></param>
        void Add(T item);
        /// <summary>
        /// 出栈
        /// </summary>
        /// <returns>出栈元素</returns>