protected void Button1_Click(object sender, EventArgs e)
{

    string conString = "Provider=Microsoft.Jet.OLEDB.4.0;"
    + "Data Source=D:/Sito/Sito/App_Data/ASPNetDB.mdb";

    OleDbConnection empConnection = new OleDbConnection(conString);


    string insertStatement = "INSERT INTO Auto "
    + "(Marca, Modello, Carburante, Kilometri, Colore, Descrizione, HomePage, Attivo) "
    + "VALUES (?, ?, ?, ?, ?, ?, ?, ?)";

    string retreiveStatement = "SELECT @@IDENTITY";

    OleDbCommand insertCommand = new OleDbCommand(insertStatement, empConnection);
    OleDbCommand retreiveCommand = new OleDbCommand(retreiveStatement, empConnection);

    insertCommand.Parameters.Add("Marca", OleDbType.Char).Value = DropDownList1.SelectedValue;
    insertCommand.Parameters.Add("Modello", OleDbType.Char).Value = DropDownList2.SelectedValue;
    insertCommand.Parameters.Add("Carburante", OleDbType.Char).Value = DropDownList3.SelectedValue;
    insertCommand.Parameters.Add("Kilometri", OleDbType.Char).Value = TextBox1.Text;
    insertCommand.Parameters.Add("Colore", OleDbType.Char).Value = DropDownList5.SelectedValue;
    insertCommand.Parameters.Add("Descrizione", OleDbType.Char).Value = TextBox2.Text;
    insertCommand.Parameters.Add("HomePage", OleDbType.Boolean).Value = CheckBox1.Checked;
    insertCommand.Parameters.Add("Attivo", OleDbType.Boolean).Value = CheckBox1.Checked;

    empConnection.Open();

    int count = 0;
    int newID = 0;
    try
    {
        count = insertCommand.ExecuteNonQuery();
        int.TryParse(retreiveCommand.ExecuteScalar().ToString(), out newID);

    }
    catch (OleDbException ex)
    {
        lblError.Visible = true;
        lblError.Text = (ex.Message);
    }
    finally
    {
        if (insertCommand != null) insertCommand.Dispose();
        if (retreiveCommand != null) retreiveCommand.Dispose();
        empConnection.Close();
    }
    if (newID > 0)
        Response.Redirect(string.Format("AllAuto.aspx?IdAuto={0}", newID )); ///(da qui devo passare il L'idauto appena inserito)
}