Handling JSON Arrays returned from ASP.NET Web Services with jQuery
The Web Service methods that I will use revolve around cars. Having set up a web site in Visual Studio 2008, I have added a new item of type "Web Service" to the project, calling it CarService.asmx. The code-behind - CarService.cs - is automatically generated within the App_Code folder. The full code for that class file is as follows:
using System;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Web.Script.Services;
using System.Collections.Generic;
using System.Linq;
public class Car
{
public string Make;
public string Model;
public int Year;
public int Doors;
public string Colour;
public float Price;
}
/// <summary>
/// Summary description for CarService
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[ScriptService]
public class CarService : WebService
{
List<Car> Cars = new List<Car>{
new Car{Make="Audi",Model="A4",Year=1995,Doors=5,Colour="Red",Price=2995f},
new Car{Make="Ford",Model="Focus",Year=2002,Doors=5,Colour="Black",Price=3250f},
new Car{Make="BMW",Model="5 Series",Year=2006,Doors=4,Colour="Grey",Price=24950f},
new Car{Make="Renault",Model="Laguna",Year=2000,Doors=5,Colour="Red",Price=3995f},
new Car{Make="Toyota",Model="Previa",Year=1998,Doors=5,Colour="Green",Price=2695f},
new Car{Make="Mini",Model="Cooper",Year=2005,Doors=2,Colour="Grey",Price=9850f},
new Car{Make="Mazda",Model="MX 5",Year=2003,Doors=2,Colour="Silver",Price=6995f},
new Car{Make="Ford",Model="Fiesta",Year=2004,Doors=3,Colour="Red",Price=3759f},
new Car{Make="Honda",Model="Accord",Year=1997,Doors=4,Colour="Silver",Price=1995f}
};
[WebMethod]
public List<Car> GetAllCars()
{
return Cars;
}
[WebMethod]
public List<Car> GetCarsByDoors(int doors)
{
var query = from c in Cars
where c.Doors == doors
select c;
return query.ToList();
}
}
A Car class is created at the top of the code, which has a number of properties of different types: strings, ints and floats. The Web Service itself is decorated with the [ScriptService] attribute, which denotes that the service can be called from Javascript. It also ensures that the data returned is a JSON string representing a single object or an array of objects, depending on the functionality of the service.
A List<Car> is instantiated, and populated with a number of Car objects. The syntax makes use of the object and collection intitialisers that were introduced in C# 3.0. Two simple methods are each decorated with the [WebMethod] attribute. The first one simply returns the List<Car> Cars that was created, whereas the second one makes use of LINQ to return only those Cars that have the number of doors that the method accepts as a parameter. There's nothing particularly fancy or clever in any of this, except to repeat the point that the [ScriptService] attribute is vital to making the methods usable by AJAX.
The mark-up in the aspx page that will call the Web Service is extremely simple:
<form id="form1" runat="server">
<input type="button" id="Button1" value="Get Cars" />
<div id="output"></div>
</form>
All that's needed now is some Javascript for the getCars() method that has been assigned to the onclick event of the html button. This will go into the <head> section of the page:
<script type="text/javascript" src="script/jquery-1.2.6.min.js"></script>
<script type="text/javascript">
$(function() {
$('#Button1').click(getCars);
});
function getCars() {
$.ajax({
type: "POST",
url: "CarService.asmx/GetAllCars",
data: "{}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(response) {
var cars = response.d;
$('#output').empty();
$.each(cars, function(index, car) {
$('#output').append('<p><strong>' + car.Make + ' ' +
car.Model + '</strong><br /> Year: ' +
car.Year + '<br />Doors: ' +
car.Doors + '<br />Colour: ' +
car.Colour + '<br />Price: £' +
car.Price + '</p>');
});
},
failure: function(msg) {
$('#output').text(msg);
}
});
}
</script>
First, jQuery is referenced via the src attribute of the first <script> tag. Then a click event is registered with the button which will invoke the getCars() function. After that is the getCars() function that is fired when the button is clicked. It makes use of the $.ajax(options) function within jQuery, and accepts an object with a number of optional properties. type specifies the HTTP method, which in this case is POST. url specifies the URL of the Web Service, together with the web method that is being called. This is followed by the parameters, which are applied to the data property. In this case, no parameters are being passed, as we are calling the method that retrieves the entire collection of Cars. The contentType and dataType MUST be specified. Following this are two further functions: success defines what should be done if the call is successful, and failure handles exceptions that are returned.
In this case, the success callback is passed the resulting HTTP response. response in this case looks like this in FireBug:
You can see that an object with a property - d - is returned, which contains an array of objects. Each object has a __type property which tells you that it is a Car object, followed by the other properties of our Web Service Car object. The div with the id of output is emptied, in case there was clutter there from a previous ajax call. The jQuery each() function is used to iterate over the collection of objects. Each car object is accessed in turn, and its properties are written to a paragraph, which is then appended to the content of div output. the result looks like this:
We'll add a DropDownList to the aspx file, so that we can make use of the second Web Method, which retrieves cars that meet the Number of Doors criteria:
<form id="form1" runat="server">
<div>
Number of doors:
<asp:DropDownList ID="ddlDoors" runat="server">
<asp:ListItem>2</asp:ListItem>
<asp:ListItem>3</asp:ListItem>
<asp:ListItem>4</asp:ListItem>
<asp:ListItem>5</asp:ListItem>
</asp:DropDownList>
</div>
<input type="button" id="Button1" value="Get Cars" onclick="getCars();" />
<div id="output"></div>
</form>
Only two lines in the previous Javascript need to be changed and these are shown in bold:
<script type="text/javascript" src="script/jquery-1.2.6.min.js"></script>
<script type="text/javascript">
function getCars() {
$.ajax({
type: "POST",
url: "CarService.asmx/GetCarsByDoors",
data: "{doors: " + $('#<%= ddlDoors.ClientID %>').val() + " }",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(response) {
var cars = response.d;
$('#output').empty();
$.each(cars, function(index, car) {
$('#output').append('<p><strong>' + car.Make + ' ' +
car.Model + '</strong><br /> Year: ' +
car.Year + '<br />Doors: ' +
car.Doors + '<br />Colour: ' +
car.Colour + '<br />Price: £' +
car.Price + '</p>');
});
},
failure: function(msg) {
$('#output').text(msg);
}
});
}
</script>
The url option now points to the appropriate method, and a parameter is passed into the data option, which uses jQuery syntax to reference the selected value from the DropDownList. I have used inline ASP.NET tags in this case to dynamically render the ID of the DropDownList using the ClientID property, so that there will be no issues in referencing the DropDownList if this code was transferred to a User Control or another control that implements INamingContainer. Now when the page is run, and an option selected, the button click event results in just those cars matching the number of doors in the DropDownList being returned:
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Date Posted:
10 January 2009 09:09
Last Updated:
06 September 2010 22:16
Posted by:
Mikesdotnetting
Total Views to date:
170699
Comments
09 April 2009 23:19 from Shail
Nice Article!
Just one question if I need to use JSON and jQuery in ASP.Net 2.0 what all I need to do. We are still using ASP.Net 2.0
10 April 2009 08:08 from Mikesdotnetting
@Shail
In 2.0, there is no "d" object in the response, so you would access the properties of the object directly from"response".
A clearer explanation is proviced here:
http://encosia.com/2009/02/10/a-breaking-change-between-versions-of-aspnet-ajax/
10 April 2009 10:23 from viet
That's great! Thank you.
10 April 2009 14:57 from Dan Sylvester
Really cool Mike. Those are great webmethod examples written in linq!
11 April 2009 12:36 from Nasir
Great mike Thank you very much
13 April 2009 06:42 from Gufran Sheikh
Hi,
Nice Article, but isn't it be good to have the returned data directly in the Object Datasource or in Dataset that is connected to the GridView, Details View, Repeater or any Data Controls ?
Because here you are generating the html in the code which is good for small forms but for large forms I dont think so it will be good idea.
Please advice.
Thanks
Gufran Sheikh
13 April 2009 08:56 from Mikesdotnetting
@Gufran
No. The whole point of the article is to illustrate how to manage this using client-side technology. Using server-side technology requires postbacks. It also forces all the processing and html generation to be done on the web server for all visitors. The approach illustrated above distributes the html generation to individual user's PCs.
If you used ASP.NET AJAX, you could bind data using a DataSource control, but then you would be returning all the html as well as the data - as well as posting a whole mess of stuff between calls such as ViewState etc. I've seen many posts in forums complaining of poor performance when people have shoved a GridView in an UpdatePanel and then bound it before the html is returned back to the browser. jQuery solves that problem.
In my view, ASP.NET AJAX is quite horrible. However, in the next version of ASP.NET (4.0) Microsoft will be introducing client-side templates where you can bind the data to a table or similar and generate the html on the client. There are a number of jQuery plugins already that allow you to do the same thing.
16 April 2009 02:04 from Paul Speranza
Mike,
I am new to JQuery and so far I have been doing my callbacks exactly the way that you are showing.
My question is, the webmethod attribut seems to work fine but I have just found out about JSON.Net. Why would we even need that?
16 April 2009 14:54 from Mikesdotnetting
@Paul,
Why should we bother about what? JSON.NET? Or the WebMethod attribute? It's actually the [ScriptService] attribute that enables the web service to return JSON formatted data (instead of SOAP messages) through a proxy that is automatically generated on behalf of the service.
21 June 2009 06:15 from wiglebot
This example helps me out on many issues I have been working through the last few days. Thanks.
22 June 2009 10:35 from Sangam Uprety
Nice article.
I have coded to fetch data in json format, but it is throwing error. However, I have been successful at retrieving the required data in the xml format. The response as tracked by firebug is:
Post: {property: 200 }
Response: System.InvalidOperationException: Request format is invalid: application/json; charset=utf-8. at System.Web.Services.Protocols.HttpServerProtocol.ReadParameters() at System.Web.Services.Protocols.WebServiceHandler.CoreProcessRequest()
Here is my ajax call:
function getData() {
$.ajax({
type: "POST",
url: "WebService.asmx/FetchDataByType",
data: {'property':200},
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(response) {
var vars = (typeof response.d) == 'string' ? eval('(' + response.d + ')') : response.d;
for (var i = 0; i < vars.length; i++) {
$('#Output').append(vars[i].Name+','+vars[i].DateCreated);
}
},
failure: function(msg) {
alert(response);
}
});
}
What could be the reason? Thank you.
26 November 2009 17:39 from RGuillen
@Sangam Uprety
You should try to add httpHandlers section to Web.config file like this:
Hope it helps.
03 March 2010 09:38 from Mayur Unagar
Thanks a lot! Very nice article. My whole day headache overcome after reading this article.
19 March 2010 10:57 from Adil Saud
Very good article,
I like the way information has been fetched from web service, specially without taking the static web reference OR instantiating web service's method dynamically at code behind end.
Thanx,
Adil...:))
30 April 2010 15:18 from rakibul Islam
Very nice article that i was looking for. many thanks
11 May 2010 16:53 from Nathan Prather
Great Article, Thanks!
Nathan
01 June 2010 01:10 from Vlad
Thanks Man.
21 June 2010 21:03 from Richard
great article!!!
04 September 2010 20:58 from Edmilson
Hi, I lost almost one day looking for this answer,
Thanks!
Edmilson
17 November 2010 11:33 from karl
wiked woking example, woop. im rocking now.......
thanks very much very good example......
21 March 2011 19:37 from David
Thanks for posting this helpful article.
To make it even more "real-world", would you mind explaining the diifferences required if the data was obtained from a database, ie how would you send a DataTable in json format?
21 March 2011 20:12 from Mikesdotnetting
@David
If you serialize a DataTable, you get XML. But I should maybe update this article to discuss serialising data to JSON using the JavaScriptSerializer class for serializing POCO classes.
31 March 2011 08:11 from Atul Kumar Singhal
How to reverse of it.
That means : How to send array object from javascript using ajax and how to get by C# of this object.
Please send me any link to reverse query.
03 April 2012 02:43 from Ghulam Haider
Excellent article with simple and to the point description.....!
Thanks.
13 June 2012 08:21 from Juber N. Mulani
working since last 3 days on this
u solved my problem
thanks a ton !!!!
26 August 2012 12:38 from Madhusudan
Thanks.... This article is really very helpful to all... This gives the the clear and exact knowledge what i was looking for. thanks once again...
11 January 2013 05:22 from Asif Iqbal
Awesome technique. I had been finding since long..
Thank you.
12 February 2013 20:10 from Altaf Patel
nice example. clean and brief.