Populate an ASP.NET ListBox from JSON results using jQuery
Note that for demonstration purposes, I have included jQuery code in the same page. Ideally, these resources should be created in separate folders for maintainability.
Let us quickly jump to the solution and see how to populate an ASP.NET ListBox from data coming from a JSON Serialized ASP.NET Web Service
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title>Populate a ListBox from JSON Results</title>
<script language="javascript" type="text/javascript"
src="http://code.jquery.com/jquery-latest.js"></script>
<script type="text/javascript">
$(function() {
var firstParam = 'F';
var radBtn = $("table.tbl input:radio");
var lBox = $('select[id$=lb]');
$(radBtn).click(function() {
lBox.empty();
var firstParam = $(':radio:checked').val();
$.ajax({
type: "POST",
url: "Services/EmployeeList.asmx/FetchEmpOnGender",
data: "{empSex:\"" + firstParam + "\"}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(msg) {
var gender = msg.d;
if (gender.length > 0) {
var listItems = [];
for (var key in gender) {
listItems.push('<option value="' +
key + '">' + gender[key].FName
+ '</option>');
}
$(lBox).append(listItems.join(''));
}
else {
alert("No records found");
}
},
error: function(XMLHttpRequest, textStatus, errorThrown) {
alert(textStatus);
}
});
});
});
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<h2>Click on a Radio Button to retrieve 'Gender' based data</h2>
<br /><br />
<asp:RadioButtonList ID="rbl" runat="server" class="tbl"
ToolTip="Click on this RadioButton to retrieve data">
<asp:ListItem Text="Male" Value="M"></asp:ListItem>
<asp:ListItem Text="Female" Value="F"></asp:ListItem>
</asp:RadioButtonList><br />
<asp:ListBox ID="lb" runat="server"></asp:ListBox>
</div>
</form>
</body>
</html>
In this example, we will see how to consume an ASP.NET Web Service (EmployeeList.asmx) that is JSON Serialized. The data source for this web service is List<Employees> in the Employee.cs class. The class can be downloaded from the source code available with this article. Here’s a snapshot of what the class looks like
If you look at the EmployeeList.cs file, you will observe that the method has been decorated with the [WebMethod] attribute to allow calls from client script
C#
[WebMethod]
public List<Employee> FetchEmpOnGender(char empSex)
{
var emp = new Employee();
var fetchEmp = emp.GetEmployeeList()
.Where(m => m.Sex == empSex);
return fetchEmp.ToList();
}
VB.NET
<WebMethod> _
Public Function FetchEmpOnGender(ByVal empSex As Char) As List(Of Employee)
Dim emp = New Employee()
Dim fetchEmp = emp.GetEmployeeList().Where(Function(m) m.Sex = empSex)
Return fetchEmp.ToList()
End Function
The FetchEmpOnGender() method calls the GetEmployeeList() method on the Employee class which returns a List<Employee>. The UI contains two radio buttons ‘Male’ and ‘Female’ which when selected, passes in the gender information to the web service. Depending on the input received, the web service method filters and returns data for the gender requested.
Note: If a method is not marked with [ScriptMethod] attribute, the method will be called by using the HTTP POST command and the response will be serialized as JSON.
To consume this web service using jQuery $.ajax(), two important points to note is that the request should be a POST request and the request’s content-type must be ‘application/json; charset=utf-8’. The code structure looks similar to the following:
$.ajax({
type: "POST",
url: "Services/EmployeeList.asmx/FetchEmpOnGender",
data: "{empSex:\"" + firstParam + "\"}",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(msg) {
},
error: function(XMLHttpRequest, textStatus, errorThrown) {
}
Also observe the way we are passing in the gender parameter using a ‘special formatting’ in the $.ajax() call
data: "{empSex:\"" + firstParam + "\"}"
Once we receive the results, we loop through it and populate an array ‘listItems’ with the FirstName values by passing in a key to the FName value (gender[key].FName))
success: function(msg) {
var gender = msg.d;
if (gender.length > 0) {
var listItems = [];
for (var key in gender) {
listItems.push('<option value="' +
key + '">' + gender[key].FName
+ '</option>');
}
The final step is to populate the ListBox using the populated array
$(lBox).append(listItems.join(''));
When you run the application, click on the radio button, to retrieve the FirstName of Employees. Clicking on the ‘Male’ radio button fetches the following results:
Whereas clicking on the ‘Female’ radio button fetches the following results:
This article has been editorially reviewed by Suprotim Agarwal.
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Suprotim Agarwal, MCSD, MCAD, MCDBA, MCSE, is the founder of
DotNetCurry,
DNC Magazine for Developers,
SQLServerCurry and
DevCurry. He has also authored a couple of books
51 Recipes using jQuery with ASP.NET Controls and
The Absolutely Awesome jQuery CookBook.
Suprotim has received the prestigious Microsoft MVP award for Sixteen consecutive years. In a professional capacity, he is the CEO of A2Z Knowledge Visuals Pvt Ltd, a digital group that offers Digital Marketing and Branding services to businesses, both in a start-up and enterprise environment.
Get in touch with him on Twitter @suprotimagarwal or at LinkedIn