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jQuery and ASP.NET AJAX PageMethods
In ASP.NET AJAX there are two ways to make AJAX calls to retrieve data from server side – Web Services and Page Methods. For the project I am working on, based on the design and flexibility for page developers, I use PageMethods to query data from the server side and it worked well. But there is one minor issue with PageMethods – you can’t assign Javascript inner functions for the success and error callbacks. It’s not a big deal, but I like the way that Google Map uses closures. So I searched for alternatives and I found jQuery has the ajax() function which is what I need.
Here I build two pages – one uses PageMethods, another used jQuery – for comparison of the syntax and usage.
I use two basic container classes for my data passed between client and server:
using System;
namespace Posts
{
[Serializable]
public class LatLong
{
public double? latitude;
public double? longitude;
}
}
using System;
namespace Posts
{
[Serializable]
public class MapView
{
public LatLong center;
public int? zoom;
}
}
The MapViewData class provides a static method to generate random map view data:
using System;
using System.Collections;
using System.Collections.Generic;
namespace Posts
{
public class MapViewData
{
public const double DefaultLatitude = 49.266214d;
public const double DefaultLongitude = -122.998577d;
public const int DefaultZoom = 12;
public static List<MapView> GenerateMapViewData(int count)
{
List<MapView> data = new List<MapView>();
Random rand = new Random();
for (int i = 0; i < count; i++)
{
double delta = rand.NextDouble() * 0.001d;
LatLong latlong = new LatLong();
latlong.latitude = DefaultLatitude + delta;
latlong.longitude = DefaultLongitude + delta;
MapView view = new MapView();
view.center = latlong;
view.zoom = DefaultZoom;
data.Add(view);
}
return (data);
}
}
}
The following static page method is in both ASP.NET AJAX and jQuery pages for return a collection of MapView objects to Javascript:
[WebMethod]
public static List<MapView> GetMapViewData(int count)
{
return (MapViewData.GenerateMapViewData(count));
}
The first example is the ASP.NET AJAX with PageMethods. Couple things to notice:
- EnablePageMethods=”true” in the ScriptManger – to enable the static page methods in ASP.NET page can be called from Javascript.
- In success_callback, the result is the collection of MapView objects. We can loop through the collection and access properties of each object.
<%@ Page Language=”C#” AutoEventWireup=”true” CodeBehind=”Compare1.aspx.cs” Inherits=”Posts.Compare1″ %>
<!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 runat=”server”>
<title>ASP.NET AJAX</title>
<script type=”text/javascript”>
function get_mapview_data(count)
{
PageMethods.GetMapViewData(
count,
success_callback,
error_callback
);
}
function success_callback(result, context, method)
{
var sb = new Sys.StringBuilder();
for (var i in result) {
sb.append(“center -> (“ + result[i].center.latitude + “, “ + result[i].center.longitude + “), “);
sb.append(“zoom -> “ + result[i].zoom);
sb.append(“<br/>”);
}
$get(“mapview_data”).innerHTML = sb.toString();
}
function error_callback(error, context, method)
{
$get(“mapview_data”).innerHTML = “Error –> “ + error.get_message();
}
</script>
</head>
<body>
<form id=”form1″ runat=”server”>
<asp:ScriptManager ID=”ScriptManager1″ runat=”server” EnablePageMethods=”true” />
<div>
<a href=”javascript:get_mapview_data(20);”>Get MapView data</a>
</div>
<br />
<div id=”mapview_data”></div>
</form>
</body>
</html>
The second example isjQuery with PageMethods. Couple things to notice too:
- The URL to request is the current page URL concatenated with “/PageMethodName”.
- I use JSON2 Javascript library to parse (deserialize) the XmlHttpRequest object returned in the error callback. You can use Sys.Serialization.JavaScriptSerializer.deserialize() to do the same thing here.
- There is no need to use ScriptManager.
<%@ Page Language=”C#” AutoEventWireup=”true” CodeBehind=”Compare2.aspx.cs” Inherits=”Posts.Compare2″ %>
<!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 runat=”server”>
<title>jQuery</title>
<script type=”text/javascript” src=”/JavaScript/jquery-1.2.6.min.js”></script>
<script type=”text/javascript” src=”/JavaScript/json2.js”></script>
<script type=”text/javascript”>
function get_mapview_data(count)
{
$.ajax({
type: “POST”,
url: window.location.href + “/GetMapViewData”,
data: “{\”count\”:\”" + count + “\”}”,
contentType: “application/json; charset=utf-8″,
dataType: “json”,
success: function(xhr, status) {
var sb = “”;
for (var i in xhr) {
sb += “center -> (“ + xhr[i].center.latitude + “, “ + xhr[i].center.longitude + “), “;
sb += “zoom -> “ + xhr[i].zoom;
sb += “<br/>”;
}
$(“#mapview_data”).html(sb);
},
error: function(xhr, status, error) {
var err = JSON.parse(xhr.responseText);
$(“#mapview_data”).html(“Error –> “ + err.Message);
}
});
}
</script>
</head>
<body>
<form id=”form1″ runat=”server”>
<div>
<a href=”javascript:get_mapview_data(20);”>Get MapView data</a>
</div>
<br />
<div id=”mapview_data”></div>
</form>
</body>
</html>
I use Firebug to check the Post and Response in both XmlHttpRequests, they are the same in both pages.
