//调用
this.Controls.Find<Button>(true).ForEach((btn) => { btn.Enabled = false; });


//定义
public static class FormControlExtensions
    {
        /// <summary>
        /// 获得指定类型的孩子控件
        /// </summary>
        /// <typeparam name="TChild">子控件类型</typeparam>
        /// <param name="controlCollection"></param>
        /// <param name="searchAllChildren">如果搜索所有子控件，则为 true；否则为 false。默认为false。</param>
        /// <returns></returns>
        public static List<TChild> Find<TChild>(this Control.ControlCollection controlCollection, bool searchAllChildren = false) 
            where TChild : Control
        {
            var children = new List<TChild>();
            _Find(controlCollection, ref children, searchAllChildren);
            return children;
        }

        /// <summary>
        /// 查询指定类型的子控件（支持递归）
        /// </summary>
        /// <typeparam name="TChild">子控件类型</typeparam>
        /// <param name="controlCollection"></param>
        /// <param name="children"></param>
        /// <param name="searchAllChildren">如果搜索所有子控件，则为 true；否则为 false。默认为false。</param>
        private static void _Find<TChild>(Control.ControlCollection controlCollection, ref List<TChild> children, bool searchAllChildren = false) 
            where TChild : Control
        {
            foreach (Control control in controlCollection)
            {
                if (control is TChild)
                {
                    children.Add((TChild)control);
                }

                if (control.Controls.Count > 0 && searchAllChildren)
                {
                    _Find(control.Controls, ref children, searchAllChildren);
                }
            }
        }
    }