petshop4学习_重构DataList实现分页

掌握要点: <IList>,DataGrid翻页事件...
详细代码如下,慢慢体会..

using System;
using System.Collections;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace CustomControl
{
    /**//// <summary>
    /// CustomList 的摘要说明
    /// 重构DataList控件
    /// </summary>
    public class CustomList : DataList
    {
        //静态常量
        protected const string HTML1 = "<table width=100% cellpadding=0 cellspacing=0><tbody><tr><td>";
        protected const string HTML2 = "</td></tr><tr><td align=right>";
        //protected const string HTML3 = "</td><td align=center class=paging>";

        //protected const string HTML5 = "</td><td align=right class=paging>";

        protected const string HTML4 = "</td></tr></tbody></table>";

        private static readonly Regex RX = new Regex(@"^&page=\d+", RegexOptions.Compiled);
        private const string LINK_PREV = "<a href=?page={0}>前一页</a>";
        private const string LINK_MORE = "<a href=?page={0}>下一页</a>";
        private const string LINK_FIRST = "<a href=?page={0}>首页</a>";     //首页
        private const string LINK_LAST = "<a href=?page={0}>尾页</a>";      //尾页
        private const string KEY_PAGE = "page";
        private const string COMMA = "?";
        private const string AMP = "&";

        protected string emptyText;
        private IList dataSource;       //数据源
        private int pageSize = 10;      //每页大小
        private int currentPageIndex;   //当前页
        private int itemCount;          //数据条目总数

        /**//// <summary>
        /// 指定要绑定的数据源
        /// </summary>
        override public object DataSource
        {
            set
            {
                //This try catch block is to avoid issues with the VS.NET designer
                //The designer will try and bind a datasource which does not derive from ILIST
                try
                {
                    dataSource = (IList)value;
                    ItemCount = dataSource.Count;
                }
                catch
                {
                    dataSource = null;
                    ItemCount = 0;
                }
            }
        }

        /**//// <summary>
        /// 每页大小
        /// </summary>
        public int PageSize
        {
            get { return pageSize; }
            set { pageSize = value; }
        }

        /**//// <summary>
        /// 总页数
        /// </summary>
        protected int PageCount
        {
            get { return (ItemCount - 1) / pageSize; }
        }

        /**//// <summary>
        /// 可重载,数据条目总数
        /// </summary>
        virtual protected int ItemCount
        {
            get { return itemCount; }
            set { itemCount = value; }
        }

        /**//// <summary>
        /// 可重载,当前页码
        /// </summary>
        virtual public int CurrentPageIndex
        {
            get { return currentPageIndex; }
            set { currentPageIndex = value; }
        }

        /**//// <summary>
        /// 空Text
        /// </summary>
        public string EmptyText
        {
            set { emptyText = value; }
        }

        /**//// <summary>
        /// 设置页面,翻页事件
        /// </summary>
        /// <param name="index"></param>
        public void SetPage(int index)
        {
            OnPageIndexChanged(new DataGridPageChangedEventArgs(null, index));
        }

        override protected void OnLoad(EventArgs e)
        {
            if (Visible)
            {
                string page = Context.Request[KEY_PAGE];
                int index = (page != null) ? int.Parse(page) : 0;
                SetPage(index);
            }
        }


        /**//// <summary>
        /// Overriden method to control how the page is rendered
        /// Render提交写入
        /// </summary>
        /// <param name="writer"></param>
        override protected void Render(HtmlTextWriter writer)
        {

            //Check there is some data attached
            if (ItemCount == 0)
            {
                writer.Write(emptyText);
                return;
            }

            //Mask the query "?"/"&"二个符号
            string query = Context.Request.Url.Query.Replace(COMMA, AMP);
            //正则表达式替换
            query = RX.Replace(query, string.Empty);


            // Write out the first part of the control, the table header
            writer.Write(HTML1);

            // Call the inherited method
            base.Render(writer);

            // Write out a table row closure
            writer.Write(HTML2);

            if (currentPageIndex > 0)
            writer.Write(string.Format(LINK_FIRST, 0 + query) + "&nbsp;");     //首页
            //Determin whether next and previous buttons are required
            //Previous button?
            if (currentPageIndex > 0)
                writer.Write(string.Format(LINK_PREV, (currentPageIndex - 1) + query));

            //Close the table data tag
            //writer.Write(HTML3);

            //当前页/总页数
            writer.Write("&nbsp;&nbsp;" + string.Format("页码:{0}/{1}", currentPageIndex + 1, PageCount + 1) + "&nbsp;&nbsp;");

            //writer.Write(HTML5);

            //Next button?
            if (currentPageIndex < PageCount)
                writer.Write(string.Format(LINK_MORE, (currentPageIndex + 1) + query));
            if (currentPageIndex < PageCount)
            writer.Write("&nbsp;" + string.Format(LINK_LAST, PageCount + query));      //尾页

            //Close the table
            writer.Write(HTML4);
        }

        override protected void OnDataBinding(EventArgs e)
        {

            //Work out which items we want to render to the page
            int start = CurrentPageIndex * pageSize;
            int size = Math.Min(pageSize, ItemCount - start);

            IList page = new ArrayList();

            //Add the relevant items from the datasource
            for (int i = 0; i < size; i++)
                page.Add(dataSource[start + i]);

            //set the base objects datasource
            base.DataSource = page;
            base.OnDataBinding(e);

        }

        /**//// <summary>
        /// 翻页事件
        /// </summary>
        public event DataGridPageChangedEventHandler PageIndexChanged;

        /**//// <summary>
        /// 可重载,翻页事件处理
        /// </summary>
        /// <param name="e"></param>
        virtual protected void OnPageIndexChanged(DataGridPageChangedEventArgs e)
        {
            if (PageIndexChanged != null)
                PageIndexChanged(this, e);
        }
    }
}