In this tutorial, I’ll explain dropdownlist cascading in form of country-state-city that depends on one another in asp.net using c# as well as vb.net with example code.
In my previous tutorials, I’d explained about cascading country-state-city for dropdownlist without page refresh, dynamically bind and show data in dropdownlist, main differences between executereader executenonquery and executescalar and other more cracking tutorials on DropDownList, GridView, Asp.net here.
To explain further about cascading asp.net dropdownlist for country-state-city, we need to create database table to get data and bind retrieved resultset to dropdown list based on dropdown selections, so check out the following image that shows the relationship between country-state-city tables one another. If you want the database tables sample script, download sample code at the end of tutorial else do it by yourself.
HTML Markup For Asp.net DropDownList Cascading – [.aspx]
Following is the complete HTML Markup code that I used for this demonstration for asp.net dropdownlist cascading in my .aspx page:
<head id=”Head1″ runat=”server”>
<title>Simple cascading country-state-city dropdownlist example
in asp.net</title>
</head>
<body>
<form id=”form1″ runat=”server”>
<div>
<h4>
Simple cascading country-state-city dropdownlist example in asp.net</h4>
<table>
<tr>
<td>
Select Country:
<asp:DropDownList ID=”ddlCountry” runat=”server” AutoPostBack=”true”
OnSelectedIndexChanged=”ddlCountry_SelectedIndexChanged”>
</asp:DropDownList>
</td>
</tr>
<tr>
<td>
Select State:
<asp:DropDownList ID=”ddlState” runat=”server” AutoPostBack=”true”
OnSelectedIndexChanged=”ddlState_SelectedIndexChanged”>
</asp:DropDownList>
</td>
</tr>
<tr>
<td>
Select City:
<asp:DropDownList ID=”ddlCity” runat=”server”>
</asp:DropDownList>
</td>
</tr>
</table>
</div>
</form>
</body>
</html>
Now check the below sample code snippet to bind cascading country-state-city of asp.net dropdown list.
Country-State-City DropDownList Cascading In C# – [.cs]
Now add the following namespace that is required to connect with sql server:
using System.Data.SqlClient;
After that add the following code to .aspx.cs page:
public static string strConn =
@”Data Source=datasource;Integrated Security=true;Initial Catalog=database”;
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindCountryList();
}
}//bind countries to country dropdownlist
private void BindCountryList()
{
try
{
using (SqlConnection sqlConn = new SqlConnection(strConn))
{
using (SqlCommand sqlCmd = new SqlCommand())
{
sqlCmd.CommandText = “SELECT CountryId,CountryName FROM Country”;
sqlCmd.Connection = sqlConn;
sqlConn.Open();
SqlDataAdapter da = new SqlDataAdapter(sqlCmd);
DataTable dt = new DataTable();
da.Fill(dt);
ddlCountry.DataSource = dt;
ddlCountry.DataValueField = “CountryId”;
ddlCountry.DataTextField = “CountryName”;
ddlCountry.DataBind();
sqlConn.Close();
//Adding “Please select country” option in dropdownlist
ddlCountry.Items.Insert(0, new ListItem(“Please select country”, “0”));
//Adding initially value to “state” and “city” dropdownlist
ddlState.Items.Insert(0, new ListItem(“Please select state”, “0”));
ddlCity.Items.Insert(0, new ListItem(“Please select city”, “0”));
}
}
}
catch { }
}
//bind states to state dropdownlist on country change event
protected void ddlCountry_SelectedIndexChanged(object sender, EventArgs e)
{
try
{
using (SqlConnection sqlConn = new SqlConnection(strConn))
{
using (SqlCommand sqlCmd = new SqlCommand())
{
sqlCmd.CommandText = @”SELECT StateId,StateName FROM State
WHERE CountryId=@CountryId”;
sqlCmd.Parameters.AddWithValue(“@CountryId”, ddlCountry.SelectedValue);
sqlCmd.Connection = sqlConn;
sqlConn.Open();
SqlDataAdapter da = new SqlDataAdapter(sqlCmd);
DataTable dt = new DataTable();
da.Fill(dt);
ddlState.DataSource = dt;
ddlState.DataValueField = “StateId”;
ddlState.DataTextField = “StateName”;
ddlState.DataBind();
sqlConn.Close();
//Adding “Please select state” option in dropdownlist
ddlState.Items.Insert(0, new ListItem(“Please select state”, “0”));
//also clear city dropdownlist because we are changing country
ddlCity.Items.Clear();
ddlCity.Items.Insert(0, new ListItem(“Please select city”, “0”));
}
}
}
catch { }
}
//bind cities to city dropdownlist on state change event
protected void ddlState_SelectedIndexChanged(object sender, EventArgs e)
{
try
{
using (SqlConnection sqlConn = new SqlConnection(strConn))
{
using (SqlCommand sqlCmd = new SqlCommand())
{
sqlCmd.CommandText = @”SELECT CityId,CityName FROM City
WHERE StateId=@StateId”;
sqlCmd.Parameters.AddWithValue(“@StateId”, ddlState.SelectedValue);
sqlCmd.Connection = sqlConn;
sqlConn.Open();
SqlDataAdapter da = new SqlDataAdapter(sqlCmd);
DataTable dt = new DataTable();
da.Fill(dt);
ddlCity.DataSource = dt;
ddlCity.DataValueField = “CityId”;
ddlCity.DataTextField = “CityName”;
ddlCity.DataBind();
sqlConn.Close();
//Adding “Please select city” option in dropdownlist
ddlCity.Items.Insert(0, new ListItem(“Please select city”, “0”));
}
}
}
catch { }
}
Country-State-City DropDownList Cascading In Vb.net – [.vb]
Now add the following namespace that is required to connect with sql server:
After that add the following code to .aspx.vb page:
Public Shared strConn As String =
“Data Source=datasource;Integrated Security=true;Initial Catalog=database”
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not IsPostBack Then
BindCountryList()
End If
End Sub‘bind countries to country dropdownlist
Private Sub BindCountryList()
Try
Using sqlConn As New SqlConnection(strConn)
Using sqlCmd As New SqlCommand()
sqlCmd.CommandText = “SELECT CountryId,CountryName FROM Country”
sqlCmd.Connection = sqlConn
sqlConn.Open()
Dim da As New SqlDataAdapter(sqlCmd)
Dim dt As New DataTable()
da.Fill(dt)
ddlCountry.DataSource = dt
ddlCountry.DataValueField = “CountryId”
ddlCountry.DataTextField = “CountryName”
ddlCountry.DataBind()
sqlConn.Close()
‘Adding “Please select country” option in dropdownlist
ddlCountry.Items.Insert(0, New ListItem(“Please select country”, “0”))
‘Adding initially value to “state” and “city” dropdownlist
ddlState.Items.Insert(0, New ListItem(“Please select state”, “0”))
ddlCity.Items.Insert(0, New ListItem(“Please select city”, “0”))
End Using
End Using
Catch
End Try
End Sub
‘bind states to state dropdownlist on country change event
Protected Sub ddlCountry_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
Try
Using sqlConn As New SqlConnection(strConn)
Using sqlCmd As New SqlCommand()
sqlCmd.CommandText = “SELECT StateId,StateName FROM State “ &
“WHERE CountryId=@CountryId”
sqlCmd.Parameters.AddWithValue(“@CountryId”, ddlCountry.SelectedValue)
sqlCmd.Connection = sqlConn
sqlConn.Open()
Dim da As New SqlDataAdapter(sqlCmd)
Dim dt As New DataTable()
da.Fill(dt)
ddlState.DataSource = dt
ddlState.DataValueField = “StateId”
ddlState.DataTextField = “StateName”
ddlState.DataBind()
sqlConn.Close()
‘Adding “Please select state” option in dropdownlist
ddlState.Items.Insert(0, New ListItem(“Please select state”, “0”))
‘also clear city dropdownlist because we are changing country
ddlCity.Items.Clear()
ddlCity.Items.Insert(0, New ListItem(“Please select city”, “0”))
End Using
End Using
Catch
End Try
End Sub
‘bind cities to city dropdownlist on state change event
Protected Sub ddlState_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
Try
Using sqlConn As New SqlConnection(strConn)
Using sqlCmd As New SqlCommand()
sqlCmd.CommandText = “SELECT CityId,CityName FROM City “ &
“WHERE StateId=@StateId”
sqlCmd.Parameters.AddWithValue(“@StateId”, ddlState.SelectedValue)
sqlCmd.Connection = sqlConn
sqlConn.Open()
Dim da As New SqlDataAdapter(sqlCmd)
Dim dt As New DataTable()
da.Fill(dt)
ddlCity.DataSource = dt
ddlCity.DataValueField = “CityId”
ddlCity.DataTextField = “CityName”
ddlCity.DataBind()
sqlConn.Close()
‘Adding “Please select city” option in dropdownlist
ddlCity.Items.Insert(0, New ListItem(“Please select city”, “0”))
End Using
End Using
Catch
End Try
End Sub
Example Result
