function DoPostBack() {
               __doPostBack();
             }

    Private Sub ImageButtonRicerca_Click(sender As Object, e As System.Web.UI.ImageClickEventArgs) Handles ImageButtonRicerca.Click
        ScriptManager.RegisterStartupScript(Page, Me.GetType, "postback", "DoPostBack();", True)
        _search.Value = Txt_ricerca1.Text
        _search1.Value = txt_ricerca2.Text
        Carica_risultati(_search.Value, _search1.Value)
    End Sub