ASP.NET

<%@ Page Title="" Language="VB" MasterPageFile="~/MyMaster.master" AutoEventWireup="false" CodeFile="MyPage.aspx.vb" Inherits="MyPage" EnableViewState="true" %>
 
<asp:Content ID="Content1" ContentPlaceHolderID="MainPageContent" Runat="Server">
<center><h3>Title</h3></center><br />
 
<table width="500px">
    <tr>
        <td><asp:Label ID="Label1" Text="Label1 : " runat="server"></asp:Label></td>
         <td><asp:DropDownList ID="ddl1" Width="200px" runat="server"
                AutoPostBack="True"/></td>
    </tr>
    <tr><td></td></tr>
     <tr>
        <td><asp:Label ID="Label2" Text="Label2 : " runat="server"></asp:Label></td>
        <td><asp:DropDownList ID="ddl2" Width="200px" runat="server" 
                AutoPostBack="True" /></td>
    </tr>
    <tr><td></td></tr>
    <tr>
        <td><asp:Label ID="Label3" Text="Label3 : " runat="server"></asp:Label></td>
         <td><asp:DropDownList ID="ddl3" Width="200px" runat="server" 
                AutoPostBack="True" /></td>
    </tr>
</table><br />
 <asp:Label ID="lblError" ForeColor="Red" runat="server" />
</asp:Content>

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration.ConfigurationManager

Partial Class MyPage Inherits System.Web.UI.Page
    Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
         If IsPostBack Then
            Exit Sub
        End If
        PopulateData()
    End Sub

    Private Sub PopulateData()
        Dim da As New SqlDataAdapter
         Dim ds1, ds2, ds3 As New DataSet

        Try
            Using conn As New SqlConnection(ConnectionStrings.Item("DataConnectionString").ToString)
                Using cmd As New SqlCommand("MySP1", conn)
                     cmd.CommandType = CommandType.StoredProcedure
                    conn.Open()
                    da.SelectCommand = cmd
                    da.Fill(ds1)
                    cmd.CommandText = "MySP2"
                     da.SelectCommand = cmd
                    da.Fill(ds2)
                    cmd.CommandText = "MySP3"
                    da.SelectCommand = cmd
                    da.Fill(ds3) 
                    conn.Close()
                End Using
            End Using

            ddl1.DataSource = ds1.Tables(0)
            ddl1.DataValueField = "Col1"
            ddl1.DataTextField = "Col2"
            ddl1.DataBind()
            ddl1.Items.Insert(0, New ListItem(String.Empty, String.Empty))
            ddl1.SelectedIndex = 0

            ddl2.DataSource = ds2.Tables(0)
            ddl2.DataValueField = "Col1"
            ddl2.DataTextField = "Col2"
            ddl2.DataBind()
            ddl2.Items.Insert(0, New ListItem(String.Empty, String.Empty))
            ddl2.SelectedIndex = 0
 
            ddl3.DataSource = ds3.Tables(0)
            ddl3.DataValueField = "Col1"
            ddl3.DataTextField = "Col2"
            ddl3.DataBind()
            ddl3.Items.Insert(0, New ListItem(String.Empty, String.Empty))
            ddl3.SelectedIndex = 0

        Catch ex As Exception
            'todo get a proper error message here
            lblError.Text = "Error"
        End Try

    End Sub
 
    Protected Sub ddl_SelectedIndexChanged(sender As Object, e As System.EventArgs) Handles ddl1.SelectedIndexChanged, ddl2.SelectedIndexChanged, ddl3.SelectedIndexChanged
        ClientScript.RegisterStartupScript(Me.GetType(), "myalert", "alert('" & "test" & "');", True)
    End Sub
End Class