Cascading dropdown is the most common
requirement we use to get in the real time world. So mainly beginners feel
difficulty in doing this task. I have seen many of my friends and colleagues
face this problem. Hope this could help those folks.
Normally some folks posting the Question "How to get the Second Dropdown fill
based on the first dropdown selection?". The processing of filling the second
dropdown based on the first dropdown selection is called "Cascading Dropdown or
Filtered Dropdown". Actually the data source I have used is XML file which
contains the Country and State. In the source code this XML file is also given
please check once you download the source code.
Cascading dropdown can be done in many ways out of which i have chosen this
using jQuery. I have taken the common example of Country and States. I have
taken two Composite types as "Country" and "State" which contains properties as
ID,Name. I have given the structure also.
using
System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace CascadingExample
{
public class
Country
{
public string CountryName { get; set; }
public int CountryID { get; set; }
public List<Country>
FetchStates(string countryName)
{
return new
List<Country> { };
}
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace CascadingExample
{
public class
State
{
public State()
{
//To Do
}
public int StateID { get; set; }
public int CountryID { get; set; }
public string StateName { get; set; }
}
}
I have designed a separate class for fetching
data from the data source (XML file) based on the filtering. The name of the
class is given as the "Data Manager".
To present this example in a beautiful way i designed a screen as shown below:
![Cascading dropdown]()
I have fetched the Countries list from the XML file in the Page_load of the Page
and the method("FetchCountries") in the DataManager class.
public
List<Country>
FetchCountries()
{
List<Country> lstCountry =
new List<Country>();
XmlDocument xDoc = new XmlDocument();
xDoc.Load(xmlPath);
XmlElement root = xDoc.DocumentElement;
XmlNodeList nodeList = root.GetElementsByTagName("country");
for (int i = 0; i < nodeList.Count;
i++)
{
String countryName = String.Empty;
countryName = nodeList[i].Attributes["name"].Value;
lstCountry.Add(new
Country { CountryID = i, CountryName = countryName });
}
return lstCountry;
}
The HTML design of the CascadingExample.aspx is given below:
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="CascadingDropDown.aspx.cs"
Inherits="CascadingExample.CascadingDropDown" %>
<!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>Cascading
DropDownLists With ASP.NET and jQuery</title>
<style
type="text/css">
.ddl_style
{
text-align: justify;
font-family: Verdana;
}
.para_Style
{
text-align: justify;
}
</style>
<script
type="text/javascript"
src="http://code.jquery.com/jquery-1.4.1.js"></script>
<script
type="text/javascript">
$(document).ready(function () {
var ddl = $("select[name$=ddlCountries]");
var ddlState = $("select[name$=ddlState]");
ddl.focus();
ddl.bind("change keyup", function () {
if ($(this).val() != "-1") {
$('p[class$="para_Style"]')[0].innerText = "";
loadStates($("select[name$=ddlCountries]
option:selected").val(), $("select[name$=ddlCountries] option:selected").text());
ddlState.fadeIn("slow");
} else {
ddlState.fadeOut("slow");
}
});
});
function loadStates(selectedIndex, selectedText) {
$.ajax({
type: "POST",
url: "CascadingDropDown.aspx/FetchStates",
data: "{countryID:" + parseInt(selectedIndex) + ",countryName:'"
+ selectedText + "'}",
contentType: "application/json;char-set=utf-8",
dataType: "json",
async: true,
success: function Success(data) {
printStates(data.d);
selectedIndex = 0;
selectedText = '';
}
});
}
function printStates(data) {
$("select[name*=ddlState]>option").remove();
$("select[name*=ddlState]").append($("<option></option>").val(-1).html("(Please
Select)"));
$('p[class$="para_Style"]').append("You have Selected
<b>
" + $("select[name$=ddlCountries] option:selected").text() + "</b><br>State
List is given below:<br>");
for (var i = 0; i < data.length; i++) {
$("select[name*=ddlState]").append($("<option></option>").val(data[i].StateID).html(data[i].StateName));
$('p[class$="para_Style"]').append(data[i].StateName + "<br>");
}
}
</script>
</head>
<body>
<form
id="form1"
runat="server">
<div>
<h2
style="font-family:
Verdana; text-align: left; font-size: medium; color: Green">
An Example to show Cascading Dropdown in Asp.Net using jQuery
</h2>
<br
/>
<table
style="font-family:
Times New Roman Baltic; text-align: left; font-size: medium;
color: Red">
<tr>
<td>
<label>
Select Country</label><br
/>
</td>
<td>
<asp:DropDownList
ID="ddlCountries"
runat="server"
AppendDataBoundItems="true"
CssClass="ddl_style">
<asp:ListItem
Text="(Please
Select)" Value="-1"
Selected="True"
/>
</asp:DropDownList>
</td>
</tr>
<br
/>
<tr>
<td>
<label>
Select State</label><br
/>
</td>
<td>
<asp:DropDownList
ID="ddlState"
runat="server"
CssClass="ddl_style"
AppendDataBoundItems="true">
</asp:DropDownList>
</td>
</tr>
</table>
<p
class="para_Style">
</p>
</div>
</form>
</body>
</html>
In the Cascading Example i have designed a WebMethod and called using jQuery
AJAX POST.
[WebMethod]
public static
List<State> FetchStates(int countryID, string countryName)
{
DataManager objDataManager = new
DataManager();
List<State> stateObj =
new List<State>();
stateObj=objDataManager.FetchState(new
Country { CountryID = countryID, CountryName = countryName });
return stateObj;
}
When we run the page we will get the output like this:
![Cascading dropdown using jquery]()
To better understand this concept you need to analyse in the HTML watcher tools.
The best tool what i can say is FireFox add on FireBug. If you don't have the
firefox you need to download here(FireFox) and download the firebug add on
here(FireBug). Now follow the steps given below
- Click on the Firebug which will open in the bottom.
- Now go to the "Net" tab where you will have different tabs like Header,Response,Post,JSON.
- Now select the country in the first dropdown.
- In the Net tab you can see in the POST tab you can see the method name as "FetchStates" which takes two input parameters as countryID and countryName.
- We can see clearly the response we got in the "Response" tab .
You can see in the below image:
![Cascading dropdown in asp.net]()
![ASP.NET Cascading dropdown]()
This is how we can do the cascading dropdown in ASP.NET using jQuery.
If any queries or suggestion regarding are welcome.
Happy Coding :-)