Relational DropDownList Using VB.NET Code Example. In this code, we illustrate three steps:
Step 1. Copy and paste the code below on to the newly created aspx file
Step 2. Add <appSettings> tag to the existing web.config
Step 3. Make sure you have Northwind database install in your system******************************

 <!-- ASPX Page --><!-- Step 1. Copy and paste the code below on to the newly created aspx file --><!-- Step 2. Add <appSettings> tag to the existing web.config --><!-- Step 3. Make sure you have Northwind database install in your system --><%@ Import Namespace="System.Data" %><%@ Import Namespace="System.Data.SqlClient" %>
<SCRIPT language=VB runat="server">

Public Sub Page_Load(Source As Object, E As EventArgs)

If Not IsPostBack Then

Dim _Conn As SqlConnection
Dim _Command As SqlCommand
Dim _Reader As SqlDataReader
Dim SQL As String

SQL = "select * from Region"

_Conn = GetConnection()

_Command = new SqlCommand(SQL, _Conn)

_Reader = _Command.ExecuteReader()

Regions.Items.Add(new ListItem("Select Region...", "0")) 

While _Reader.Read()
Regions.Items.Add(new ListItem(_Reader("RegionDescription").ToString(), _Reader("RegionID").ToString()))
End While

Territory.Items.Add(new ListItem("Select Territory...", "0"))

End If

End Sub

Function GetConnection() As SqlConnection
Dim _Connection As SqlConnection
Dim ConnStr As String

ConnStr = ConfigurationSettings.AppSettings("ConnectionString")

_Connection = new SqlConnection(ConnStr)
_Connection.Open()

Return _Connection
End Function 


Sub OnSelectedRegionIndexChanged(Source As Object, E As EventArgs)
Dim _Region As Integer

_Region = Regions.SelectedItem.Value

If _Region > 0 Then 

Dim _Conn As SqlConnection
Dim _Command As SqlCommand
Dim _Reader As SqlDataReader
Dim SQL As String

SQL = "select * from Territories where RegionID ='" & _Region & "'"

_Conn = GetConnection()

_Command = new SqlCommand(SQL, _Conn)

_Reader = _Command.ExecuteReader()

Territory.Items.Clear()
Territory.Items.Add(new ListItem("Select Territory...", "0"))


While _Reader.Read()
Territory.Items.Add(new ListItem(_Reader("TerritoryDescription").ToString(), _Reader("TerritoryID").ToString()))
End While

txtRegion.Text = Regions.SelectedItem.Text 
txtTerritory.Text = "" 
Else

Territory.Items.Clear()
Territory.Items.Add(new ListItem("Select Territory...", "0"))
txtRegion.Text = ""
txtTerritory.Text = ""

End If 

End Sub

Sub OnSelectedTerritoryIndexChanged(Source As Object, E As EventArgs)

Dim _Territory As Integer

_Territory = Territory.SelectedItem.Value

If _Territory > 0 Then

txtTerritory.Text = Territory.SelectedItem.Text
Else
txtTerritory.Text = ""
End If

End Sub

</SCRIPT>

<FORM runat="server"><asp:DropDownList id=Regions runat="server" 
OnSelectedIndexChanged="OnSelectedRegionIndexChanged" 
AutoPostBack="True"></asp:DropDownList>
<asp:DropDownList id=Territory runat="server" 
OnSelectedIndexChanged="OnSelectedTerritoryIndexChanged" 
AutoPostBack="True"></asp:DropDownList>
<asp:Label id=txtRegion runat="server"></asp:Label>
<asp:Label 
id=txtTerritory 
runat="server"></asp:Label></FORM><!-- Web.Config --><CONFIGURATION><APPSETTINGS><ADD 
value="Server=(local)NetSDK;uid=sa;pwd=;database=Northwind" 
key="ConnectionString" /></APPSETTINGS></CONFIGURATION>

DISCLAIMER: The content provided in this article is not warranted or guaranteed by Developer Shed, Inc. The content provided is intended for entertainment and/or educational purposes in order to introduce to the reader key ideas, concepts, and/or product reviews. As such it is incumbent upon the reader to employ real-world tactics for security and implementation of best practices. We are not liable for any negative consequences that may result from implementing any information covered in our articles or tutorials. If this is a hardware review, it is not recommended to open and/or modify your hardware.

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