Asp.net使用JQuery实现评论的无刷新分页及分段延迟加载效果

时间：2010-10-03 来源：heqichang

本文要实现的效果就是在评论别人文章时，如果文章内容过长或者评论内容过长，实现的一个评论分段延迟加载的效果，即每页可显示30条评论，可每隔10条延迟加载一次以提高网页传输显示效率。

然后再评论末端加载上页码实现无刷新进行分页的效果。

LoadArticle.ashx：一个一般处理程序，用来加载文章内容，源代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Configuration;
using System.Data.SqlClient;
using Microsoft.ApplicationBlocks.Data;
using System.Data;
using System.Text;

namespace AJAXPagingTest
{
    /// <summary>
    /// Summary description for LoadArticle
    /// </summary>
    public class LoadArticle : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";

            //获取连接字符串
            String connString = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;
            
            //获取所要读取的文章编号
            String aid = context.Request["article"];
            SqlParameter[] sp=new SqlParameter[1];
            sp[0]=new SqlParameter("@aid",aid);

            SqlDataReader dr = SqlHelper.ExecuteReader(connString,
                CommandType.Text,
                "select Title,Article from T_Articles where AID=@aid",
                sp);

            StringBuilder sb = new StringBuilder();

            while (dr.Read())
            {
                sb.Append(dr.GetString(dr.GetOrdinal("Title")));
                sb.Append("|");
                sb.Append(dr.GetString(dr.GetOrdinal("Article")));
            }

            context.Response.Write(sb.ToString());

        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}

LoadCommentAndPaging.ashx：也是一个一般处理程序，用于加载评论，源代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data;
using System.Data.SqlClient;
using Microsoft.ApplicationBlocks.Data;
using System.Configuration;
using System.Web.Script.Serialization;


namespace AJAXPagingTest
{
    /// <summary>
    /// Summary description for LoadCommentAndPaging
    /// </summary>
    public class LoadCommentAndPaging : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";

            String connStr = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;
            List<Comment> Comments = new List<Comment>();
            String result = String.Empty;

            //获取页面的动作
            String action = context.Request["action"];
            
            //页面第一加载的时候
            if (action=="load")
            {
                DataTable dt = SqlHelper.ExecuteDataset(connStr,
                    CommandType.Text,
                    "select top(10) * from T_Comments where AID=1").Tables[0];

                foreach (DataRow dr in dt.Rows)
                {
                    Comment comment = new Comment();
                    comment.Username = dr["Username"].ToString();
                    comment.Commentz = dr["Comment"].ToString();
                    Comments.Add(comment);
                }
                JavaScriptSerializer jss = new JavaScriptSerializer();
                result = jss.Serialize(Comments);
                context.Response.Write(result);
                return;
            }

            //获取当前页码
            String pageString = context.Request["page"];

            //处理延时或分页加载评论
            if (action=="pageOrlazy")
            {
                //获取当前延时加载的次数
                String countString = context.Request["count"];

                int page, count;

                //判断参数是否正确
                if (int.TryParse(pageString, out page) && int.TryParse(countString, out count))
                {
                    //计算需要加载评论的起始索引
                    int startindex = (page - 1) * 30 + count * 10 + 1;

                    //计算需要加载评论结束索引
                    int endindex = startindex + 9;

                    SqlParameter[] sp = new SqlParameter[3];
                    sp[0] = new SqlParameter("@aid", 1);
                    sp[1] = new SqlParameter("@startindex", startindex);
                    sp[2] = new SqlParameter("@endindex", endindex);

                    DataTable dt = SqlHelper.ExecuteDataset(connStr,
                        CommandType.StoredProcedure,
                        "ps_getpageandload",
                        sp).Tables[0];

                    foreach (DataRow dr in dt.Rows)
                    {
                        Comment comment = new Comment();
                        comment.Username = dr["Username"].ToString();
                        comment.Commentz = dr["Comment"].ToString();
                        Comments.Add(comment);
                    }

                    JavaScriptSerializer jss = new JavaScriptSerializer();
                    result = jss.Serialize(Comments);
                    context.Response.Write(result);
                    return;

                }
                else
                {
                    throw new Exception("参数传递错误");
                }

            }

            //获取页码
            if (action=="pagenumber")
            {
                int number = Convert.ToInt32(SqlHelper.ExecuteScalar(connStr,
                    CommandType.Text,
                    "select count(*) from T_Comments"));

                context.Response.Write((number/30).ToString());
                return;
            }

           
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }

    public class Comment
    {
        public String Username {get;set; }
        public String Commentz {get;set; }
    }
}

CommnetPage.htm：最后是前台页面的JQuery代码

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>
    <link href="Style/StyleSheet1.css" rel="stylesheet" type="text/css" />
    <script src="JS/jquery-1.4.2.min.js" type="text/javascript"></script>
    <script type="text/javascript">
        $(function () {

            //加载文章内容
            $.post("LoadArticle.ashx", { "article": "1" }, function (data, state) {
                if (state == "success") {

                    //利用"|"来分隔标题和正文
                    var article = data.split("|");
                    $("#article h3").text(article[0]);
                    $("#article").append(article[1]);
                }
            });

            //加载初始的10条评论条数
            $.post("LoadCommentAndPaging.ashx", { "action": "load" }, function (data, state) {
                if (state == "success") {
                    var comments = $.parseJSON(data);

                    for (var i = 0; i < comments.length; i++) {
                        var comment = "<tr><td>" + comments[i].Username + "说：</td><td>" + comments[i].Commentz + "</td></tr>";
                        $("#comment").append(comment);
                    }
                }
            });
        });

        //标记页面延迟数
        var flag = 1;

        //标记当前页面
        var currentpage = 1;

        //监测是否需要加载评论
        function check(n) {

            //监测浏览器的模式，根据不同的模式获取客户端高度会有不同
            var dom = document.compatMode == "CSS1Compat" ? document.documentElement : document.body;
            var pre = document.getElementById("preload");

            //获取滚动条离顶端的高度，用IE测试时是用
            //documentElement.scrollTop获取高度，
            //而在用chrome测试时是body.scrollTop获取高度
            var scrtop = dom.scrollTop || document.body.scrollTop;

            //传入的参数为当前页数，保存为全局变量
            currentpage = n;

            //当客户端显示窗口离标记的地方小于100距离时开始加载
            if (pre.offsetTop - (dom.clientHeight + scrtop) < 100) {
                $.post("LoadCommentAndPaging.ashx", { "action": "pageOrlazy", "page": currentpage, "count": flag }, function (data, state) {
                    if (state == "success") {
                        var comments = $.parseJSON(data);
                        for (var i = 0; i < comments.length; i++) {
                            var comment = "<tr><td>" + comments[i].Username + "说：</td><td>" + comments[i].Commentz + "</td></tr>";
                            $("#comment").append(comment);
                        }
                    }
                });

                flag = flag + 1;

                //如果加载多于3次了则不加载评论了，加载页码
                if (flag <= 2) {
                    setTimeout("check(currentpage)", 2000);
                }
                else {
                    //加载页码
                    $.post("LoadCommentAndPaging.ashx", { "action": "pagenumber" }, function (data, state) {
                        if (state == "success") {
                            var count = parseInt(data, 10);

                            for (var i = 1; i <= count + 1; i++) {
                                var control;

                                //等于当前页时则不显示超链接
                                if (i != currentpage) {
                                    control = "<td><a href=''>" + i + "</a></td>";
                                }
                                else {
                                    control = "<td>" + i + "</td>";
                                }


                                $("#anchorlink").append(control);


                            }
                            //加载分页点击时的事件
                            $("#anchorlink td").click(function (e) {
                                e.preventDefault();  //阻止超链接的转向
                                $("#comment").empty();  //将评论区清空
                                $("#anchorlink").empty();  //将页码清空
                                $("#preload").text("评论正在加载中...");  
                                flag = 0;
                                var page = parseInt($(this).text());
                                check(page);

                            });

                        }
                    });
                    //去掉“评论加载中”的显示
                    $("#preload").text("");
                }
            }
            else {
                setTimeout("check(currentpage)", 2000);
            }

        }

        //每隔两秒检查一下页面是否需要加载评论
        setTimeout("check(currentpage)", 2000);

    </script>
</head>
<body>
    <div id="main">
        <div id="article">
            <h3>
            </h3>
        </div>
        <div>
            <table id="comment">
            </table>
            <p id="preload">
                评论正在加载中...</p>
            <table>
                <tr id="anchorlink">
                </tr>
            </table>
        </div>
    </div>
</body>
</html>