<form runat="server">
<asp:DropDownList ID="ddl1" onselectedindexchanged="ddl1_change" autopostback="true" runat="server" />
<asp:DropDownList ID="ddl2" runat="server" />
...
...
</form>
 
<script runat="server" language="vb">
Sub Page_Load(ByVal S As Object, ByVal E As EventArgs)
  Dim conn As New SqlConnection( connectionstring )
  Dim cmd As New SqlCommand ("SELECT company, mfgID FROM Manufacturers", conn)
  Dim dtrReader As SqlDataReader
 
  Try
    conn.Open()
    dtrReader = cmd.ExecuteReader()
    if dtrReader.HasRows then
      ddl1.DataSource = dtrReader
      ddl1.DataTextField = "company"
      ddl1.DataValueField = "mfgID"
      ddl1.DataBind()
    end if
    dtrReader.Close()
    conn.Close()
  Catch
  End Try
End Sub
 
Sub ddl1_change(ByVal S As Object, ByVal E As EventArgs)
  Dim conn As New SqlConnection( connectionstring )
  Dim cmd As New SqlCommand ("SELECT description, eqpID FROM Equipment WHERE mfgID=@mfgID", conn)
''
''However, you should change description to a name of the equipment, if there is a field for it.
''
  cmd.Parameters.AddWithValue("@mfgID", Trim(ddl1.SelectedItem.Value))
  Dim dtrReader As SqlDataReader
 
  Try
    conn.Open()
    dtrReader = cmd.ExecuteReader()
    if dtrReader.HasRows then
      ddl2.DataSource = dtrReader
      ddl2.DataTextField = "equipment"
      ddl2.DataValueField = "equipID"
      ddl2.DataBind()
    end if
    dtrReader.Close()
    conn.Close()
  Catch
  End Try
End Sub
</script>

Protected Sub DropDownList2_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DropDownList2.SelectedIndexChanged

 
 
Partial Class AddCall
    Inherits System.Web.UI.Page
    Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
        DropDownList2.SelectedIndex = 0
    End Sub
    Protected Sub DropDownList2_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DropDownList2.SelectedIndexChanged
        'labelSelection.Text = DropDownList1.SelectedItem.Text & " " & DropDownList2.SelectedItem.Text
 
        Dim Company As TextBox = TryCast(FormView1.FindControl("Company"), TextBox)
        Dim Address1 As TextBox = TryCast(FormView1.FindControl("Address1"), TextBox)
        Dim Address2 As TextBox = TryCast(FormView1.FindControl("Address2"), TextBox)
        Dim Phone As TextBox = TryCast(FormView1.FindControl("Phone"), TextBox)
        Dim FirstName As TextBox = TryCast(FormView1.FindControl("FirstName"), TextBox)
        Dim LastName As TextBox = TryCast(FormView1.FindControl("LastName"), TextBox)
        Dim City As TextBox = TryCast(FormView1.FindControl("City"), TextBox)
        Dim State As TextBox = TryCast(FormView1.FindControl("State"), TextBox)
        Dim Zip As TextBox = TryCast(FormView1.FindControl("Zip"), TextBox)
 
        Dim str_sql As String = "SELECT * FROM Customers WHERE cusID = " & DropDownList1.SelectedValue
        Using connection As New System.Data.SqlClient.SqlConnection("Data Source=IT-P02\SQLEXPRESS;Initial Catalog=HRIService;Integrated Security=True")
            Dim command As New System.Data.SqlClient.SqlCommand(str_sql, connection)
            connection.Open()
            Dim reader As System.Data.SqlClient.SqlDataReader = command.ExecuteReader()
            Try
                If reader.Read Then
                    Company.Text = reader.Item("Company").ToString
                    Address1.Text = reader.Item("Address1").ToString
                    Address2.Text = reader.Item("Address2").ToString
                    Phone.Text = reader.Item("Phone").ToString
                End If
            Finally
                ' Always call Close when done reading.
                reader.Close()
            End Try
            str_sql = "SELECT * FROM CONTACTS WHERE contactID = " & DropDownList2.SelectedValue
            command = New System.Data.SqlClient.SqlCommand(str_sql, connection)
            reader = command.ExecuteReader()
            Try
                If reader.Read Then
                    FirstName.Text = reader.Item("FirstName").ToString()
                    LastName.Text = reader.Item("LastName").ToString()
                End If
            Catch ex As Exception
                reader.Close()
            End Try
 
            reader.Close()
            str_sql = "SELECT * FROM Zip WHERE zipID = " & DropDownList1.SelectedValue
            command = New System.Data.SqlClient.SqlCommand(str_sql, connection)
            reader = command.ExecuteReader()
            Try
                If reader.Read Then
                    City.Text = reader.Item("City").ToString()
                    State.Text = reader.Item("State").ToString()
                    Zip.Text = reader.Item("Zip").ToString()
                End If
            Catch ex As Exception
                reader.Close()
            End Try
        End Using
 
    End Sub
    Protected Sub DropDownListEquip_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
 
    End Sub
 
End Class