Step 1: Create a table in database
create table test
(
state1 varchar(50),
city varchar(50)
)
Step 2: In the .aspx Page
<select id="statelist" runat="server" onchange="showCity()" style="width: 160px">
<option></option>
</select>
<asp:DropDownList ID="citylist" runat="server" Width="184px">
</asp:DropDownList>
Take statelist for State and citylist for City
When you select any item from statelist the citylist will automatically fill because of ajax
Step 3: Write this in the <head> Part
<script language="JavaScript" type="text/javascript" >
var xmlHttp
var arr;
function
showCity() {
xmlHttp = GetXmlHttpObject()
var url
= "Default.aspx"
url = url + "?name="
+ document.getElementById('statelist').value
xmlHttp.onreadystatechange =
stateChanged
xmlHttp.open("GET",
url, true)
xmlHttp.send(null)
return false;
}
function
stateChanged() {
if
(xmlHttp.readyState == 4 || xmlHttp.readyState == "complete")
{
var
str;
str = xmlHttp.responseText;
arr = str.split(",");
var
i;
for
(i = 0; i < arr.length; i++) {
dd2 = document.getElementById("citylist")
var
theOption = new Option;
theOption.text = arr[i];
theOption.value = arr[i];
dd2.options[i] = theOption;
}
}
}
function
GetXmlHttpObject() {
var
objXMLHttp = null
if
(window.XMLHttpRequest) {
objXMLHttp = new XMLHttpRequest()
}
else if (window.ActiveXObject) {
objXMLHttp = new ActiveXObject("Microsoft.XMLHTTP")
}
return
objXMLHttp
}
</script>
Step 4: In the .cs page
SqlConnection con = new SqlConnection("data source = MY\\SQLEXPRESS; initial catalog =
try; integrated security=true");
protected void Page_Load(object sender, EventArgs
e)
{
if
(!Page.IsPostBack)
{
con.Open();
SqlCommand
cmd = new SqlCommand("select * from test", con);
SqlDataReader
dr;
dr = cmd.ExecuteReader();
statelist.DataSource = dr;
statelist.DataTextField = "state";
statelist.DataBind();
dr.Close();
con.Close();
}
if
(Request.QueryString["name"] != null)
{
string name = Request.QueryString["name"];
Response.Clear();
con.Open();
SqlCommand
cmd = new SqlCommand("select * from test where state=@state",
con);
cmd.Parameters.AddWithValue("@state", name);
SqlDataReader
dr;
dr = cmd.ExecuteReader();
string
str = "";
int a =
0;
while
(dr.Read())
{
if (a == 0)
str += dr["city"].ToString();
else
str += ","
+ dr["city"].ToString();
a++;
}
Response.Write(str);
Response.End();
con.Close();
}
}