阐述返回JSON数据的使用说明介绍

第一步：为了使服务器端查询返回JSON数据，从网上找了个用C#写的JSONHelper类（在此感谢那位不知名的好人），以下是JsonHelper类全部代码。（JsonHelper.cs）

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Web.Script.Serialization;
/// <summary>
/// JSONHelper 的摘要说明
/// </summary>
public class JSONHelper
{
//对应JSON的singleInfo成员
public string singleInfo = string.Empty;
protected string _error = string.Empty;
protected bool _success = true;
protected long _totalCount = 0;
protected System.Collections.ArrayList arrData = new ArrayList();
protected System.Collections.ArrayList arrDataItem = new ArrayList();
public JSONHelper()
{
}
public static string ToJSON(object obj)
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
return serializer.Serialize(obj);
}
public static string ToJSON(object obj, int recursionDepth)
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.RecursionLimit = recursionDepth;
return serializer.Serialize(obj);
}
//对应于JSON的success成员
public bool success
{
get
{
return _success;
}
set
{
//如设置为true则清空error
if (success) _error = string.Empty;
_success = value;
}
}
//对应于JSON的error成员
public string error
{
get
{
return _error;
}
set
{
//如设置error，则自动设置success为false
if (value != "") _success = false;
_error = value;
}
}
public long totlalCount
{
get { return _totalCount; }
set { _totalCount = value; }
}
//重置，每次新生成一个json对象时必须执行该方法
public void Reset()
{
_success = true;
_error = string.Empty;
singleInfo = string.Empty;
arrData.Clear();
arrDataItem.Clear();
}
public void AddItem(string name, string value)
{
arrData.Add("/"" + name + "/":" + "/"" + value + "/"");
}
public void ItemOk()
{
arrData.Add("<BR>");
}
//序列化JSON对象，得到返回的JSON代码
public override string ToString()
{
StringBuilder sb = new StringBuilder();
sb.Append("{");
sb.Append("totalCount:" + totlalCount.ToString() + ",");
sb.Append("success:" + _success.ToString().ToLower() + ",");
sb.Append("error:/"" + _error.Replace("/"", "///"") + "/",");
sb.Append("singleInfo:/"" + singleInfo.Replace("/"", "///"") + "/",");
sb.Append("data:[");
int index = 0;
sb.Append("{");
if (arrData.Count <= 0)
{
sb.Append("}]");
}
else
{
foreach (string val in arrData)
{
index++;
if (val != "<BR>")
{
sb.Append(val + ",");
}
else
{
sbsb = sb.Replace(",", "", sb.Length - 1, 1);
sb.Append("},");
if (index < arrData.Count)
{
sb.Append("{");
}
}
}
sbsb = sb.Replace(",", "", sb.Length - 1, 1);
sb.Append("]");
}
sb.Append("}");
return sb.ToString();
}
}

第二步：新建ASPX文件，做为服务器端，用返回查询的JSON数据（PagingRequest.cs）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Text;
namespace ExtJSDemo.Data
{
public partial class PagingRequest : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
int start = Convert.ToInt32(Request["start"].ToString());   // ExtJS Paging 必须指定的参数（从第几行记录开始）/ ExtJS默认0是第一行记录
int limit = Convert.ToInt32(Request["limit"].ToString()); // ExtJS Paging 必须指定的参数（每页显示多少行记录）
JSONHelper jsonHelp = new JSONHelper();
int TotalRecords = 0;
DataSet DSet = GET_Product_Data(start, limit, out TotalRecords); // 获取数据
jsonHelp.success = true;
jsonHelp.totlalCount = TotalRecords;// 记录总数
if (DSet != null)
{
DataTable DTable = DSet.Tables[0];
for (int i = 0; i < DTable.Rows.Count; i++)
{
// 循环生成JSON代码
jsonHelp.AddItem("Id", DTable.Rows[i]["Id"].ToString());
jsonHelp.AddItem("Name", DTable.Rows[i]["Name"].ToString());
jsonHelp.AddItem("StreetPrice", DTable.Rows[i]["StreetPrice"].ToString());
jsonHelp.AddItem("TypeName", DTable.Rows[i]["TypeName"].ToString());
jsonHelp.ItemOk();
}
}
Response.Write(jsonHelp.ToString());  // 输出JSON代码
}
/// <summary>
/// 获取数据
/// </summary>
/// <param name="PageIndex">记录索引</param>
/// <param name="PageSize">每页显示记录数</param>
/// <param name="TotalRecords">总记录数</param>
public DataSet GET_Product_Data(int start, int limit,out int TotalRecords)
{
SqlConnection _Connection = null;
SqlDataAdapter _Adapter = null;
DataSet DSet = null;
try
{
_Connection = new SqlConnection(System.Configuration.ConfigurationManager.AppSettings["SQLContionString"].ToString());
_Connection.Open();
_Adapter = new SqlDataAdapter("SELECT [Id] FROM [Product] ",_Connection);
DSet = new DataSet();
_Adapter.Fill(DSet);
TotalRecords = Convert.ToInt32(DSet.Tables[0].Rows.Count);      // 记录总数
if (TotalRecords < 1) return null;  // 没有记录
int pageLowerBound = start+1;                                            // 从第几条数据开始
int pageUpperBound = pageLowerBound + limit;             // 每页多少条数据
StringBuilder sb = new StringBuilder();
if (TotalRecords >= pageLowerBound)
{
for (int i = pageLowerBound; i < TotalRecords && i < pageUpperBound; i++)
{
sb.AppendFormat("'{0}',", DSet.Tables[0].Rows[i-1][0].ToString());//构造ID in() 条件,取其中一页
}
}
else
return null; // 没有记录
if (sb.Length > 1)
sb.Remove(sb.Length - 1, 1);//删除最后一个逗号
StringBuilder strSql = new StringBuilder();
strSql.Append("SELECT a.[Id],a.[Name],a.[StreetPrice],b.TypeName  ");
strSql.Append(" FROM [Product] as a left join ProductType  as b on a.Typeid = b.Typeid ");
strSql.AppendFormat(" where a.[Id] in({0})", sb.ToString());
_Adapter = new SqlDataAdapter(strSql.ToString(), _Connection);
DSet = new DataSet();
_Adapter.Fill(DSet);
}
finally
{
if (_Connection != null && _Connection.State == ConnectionState.Open)
{
_Connection.Close();
}
}
return DSet;
}
}
}

第三步：返回JSON数据页面用作客户端呈现结果的载体(PagingControls.aspx)

<head id="Head1" runat="server">
<title></title>
<link rel="stylesheet" type="text/css" href="../ext3/resources/css/ext-all.css" mce_href="ext3/resources/css/ext-all.css" />
<mce:script type="text/javascript" src="../ext3/adapter/ext/ext-base.js" mce_src="ext3/adapter/ext/ext-base.js"></mce:script>
<mce:script type="text/javascript" src="../ext3/ext-all.js" mce_src="ext3/ext-all.js"></mce:script>
<mce:script type="text/javascript" src="JS/PagingGridPanel.js" mce_src="JS/PagingGridPanel.js"></mce:script>
<mce:script type="text/javascript"><!--
Ext.BLANK_IMAGE_URL = "../ext3/resources/images/default/s.gif";
Ext.onReady(function() {
Ext.QuickTips.init();
Ext.form.Field.prototype.msgTarget = "side";
new PagingGridPanel();      // JS文件
});

// --></mce:script>

第四部：写JS脚本！使用返回JSON数据