Private Property flag_ricerica_periodo() As Boolean
        Get
            Return CInt(ViewState("valore"))
        End Get
        Set(ByVal value As Boolean)
            ViewState("valore") = value
        End Set
    End Property
    Private Property flag_ricerica_giorno() As Boolean
        Get
            Return CInt(ViewState("valore"))
        End Get
        Set(ByVal value As Boolean)
            ViewState("valore") = value
        End Set
    End Property

    Protected Sub Page_PreLoad(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreLoad
        If Not IsPostBack Then
            txt_Arrivo.Text = Format(Now.Date, "dd/MM/yyyy")
            flag_ricerica_periodo = False : flag_ricerica_giorno = False
        End If
    End Sub