Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
    Dim WC As String
    Dim StrSql As String
    Dim AnCodice As String
    
    AnCodice = Session("AnCodice")
        
    WC = System.Configuration.ConfigurationManager.AppSettings("WC").ToString
     
    If Not Page.IsPostBack Then
      StrSql = "SELECT DISTINCT (MADESCRI), ARCODMAR FROM vst_" & WC & "_web_documenti Where MVCODCON = '" & AnCodice & "' Order By MADESCRI"
      SdsMarca.SelectCommand = StrSql

      StrSql = "SELECT DISTINCT (FADESCRI), ARCODFAM FROM vst_" & WC & "_web_documenti Where MVCODCON = '" & AnCodice & "' Order By FADESCRI"
      SdsFamiglia.SelectCommand = StrSql
    
      StrSql = "SELECT DISTINCT (GMDESCRI), ARGRUMER FROM vst_" & WC & "_web_documenti Where MVCODCON = '" & AnCodice & "' Order By GMDESCRI"
      SdsGruppo.SelectCommand = StrSql
    Else
      StrSql = "SELECT DISTINCT (FADESCRI), ARCODFAM FROM vst_" & WC & "_web_documenti Where MVCODCON = '" & AnCodice & "' and ARCODMAR='" & DdlMarca.SelectedValue & "' Order By FADESCRI"
      'Response.Write(StrSql)
      SdsFamiglia.SelectCommand = StrSql
    End If
    
  End Sub

  Protected Sub DdlMarca_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
    Dim WC As String
    Dim StrSql As String
    Dim AnCodice As String
    AnCodice = Session("AnCodice")
        
    WC = System.Configuration.ConfigurationManager.AppSettings("WC").ToString

    StrSql = "SELECT DISTINCT (FADESCRI), ARCODFAM FROM vst_" & WC & "_web_documenti Where MVCODCON = '" & AnCodice & "' and ARCODMAR='" & DdlMarca.SelectedValue & "' Order By FADESCRI"
    'Response.Write(StrSql)
    SdsFamiglia.SelectCommand = StrSql
    
    DdlFamiglia.ClearSelection()
    DdlFamiglia.DataBind()
    
    StrSql = "SELECT DISTINCT (GMDESCRI), ARGRUMER FROM vst_" & WC & "_web_documenti Where MVCODCON = '" & AnCodice & "' and ARCODMAR='" & DdlMarca.SelectedValue & "' Order By GMDESCRI"
    SdsGruppo.SelectCommand = StrSql
    
    DdlFamiglia.ClearSelection()
    DdlGruppo.DataBind()
  End Sub

<asp:DropDownList AutoPostBack="true" ID="DdlMarca" runat="server" AppendDataBoundItems="true" DataTextField="MADESCRI" DataValueField="ARCODMAR" DataSourceID="SdsMarca" OnSelectedIndexChanged="DdlMarca_SelectedIndexChanged"></asp:DropDownList>

<asp:DropDownList AutoPostBack="true" ID="DdlFamiglia" AppendDataBoundItems="true" runat="server" DataTextField="FADESCRI" DataValueField="ARCODFAM" DataSourceID="SdsFamiglia"></asp:DropDownList>

<asp:DropDownList AutoPostBack="true" ID="DdlGruppo" AppendDataBoundItems="true" runat="server" DataTextField="GMDESCRI" DataValueField="ARGRUMER" DataSourceID="SdsGruppo"></asp:DropDownList>

  <asp:SqlDataSource ID="SdsMarca" runat="server" ConnectionString="<%$ ConnectionStrings:ConnBuynet %>" />
  <asp:SqlDataSource ID="SdsFamiglia" runat="server" ConnectionString="<%$ ConnectionStrings:ConnBuynet %>" />
  <asp:SqlDataSource ID="SdsGruppo" runat="server" ConnectionString="<%$ ConnectionStrings:ConnBuynet %>" />