datagridview don't update after file.txt is updated via FTP

Question

User-350763668 posted

Hi, i have a simple file .txt in the server that populates a global list(of myobject).

In the page_init event the gridview is binded to list with:

txt_load() ' this sub reads line by line the .txt file, clear mygloballist and repopulate it with content of txtfile.

gridview1.datasource=mygloballist

gridview1.databind()

the first time that i publish the application everything works right (the gridview shows the list  correctly.)

If  i update the .txt file via ftp and i refresh page, (or i close the browser and i go in the page) the gridview still shows me the old content of file!

Even if i DELETE the .txt file (via ftp) and i go on the page, i NOT get any error (file not found for example) and the gridview always show me the old content!  Why????  I need the gridview show me the new content of .txt file after updating via ftp, and i need a error if file don't exist. Thanks.

Answer 1

User-1330468790 posted

Hi Uruse1980,

 

You should use the Page_Load event to bind the data to controls. Init and Load events have different behaviors in webforms life cycle.

• Page load event fires whenever the page is loaded for the first time, as well as when the page is posted back.
• However, the init event wont fire on postbacks

So if you really need some early initialization of a control then you can use init event.

 

Hope this helps.

Best regards,

Sean

Answer 2

User-350763668 posted

Thanks Sean, i have tried, but same result in page_load event

Answer 3

User-1330468790 posted

Hi Uruse1980,

 

Could you please share more details so that I could try to reproduce the problem?  (Or Foo/bar stuff as a replacement for secure data)

• Version of ASP.NET framework, VS and browser.
• What does the method "txt_load()" do? How it load data from the file? Any return value and type?
• What is the variable "mygloballist"? Is it a datatable?
• Have you tried to prevent caching of your web form pages? (Add below lines in Page_Load function)

Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetAllowResponseInBrowserHistory(false);

  

Best regards,

Sean

Answer 4

User-350763668 posted

Private Sub componi_Load(sender As Object, e As EventArgs) Handles Me.Load

        Dim nome As String = G_utente_loggato.nome
        
        lblutente.Text = "Ciao " & nome & "!"
        carica_alimenti("01")
        GridView1.DataSource = G_listaalimenti
        GridView1.DataBind()
        Response.Cache.SetCacheability(HttpCacheability.NoCache)
        Response.Cache.SetAllowResponseInBrowserHistory(False)

    End Sub

Public Sub carica_alimenti(filiale As String)

       
            G_listaalimenti.Clear()
            Dim vettore() As String
            Dim rigaletta As String = ""
            Dim lettorefile As New StreamReader(Server.MapPath("/pranziveloci01app/Database/" & filiale & "/alimenti.txt"))
            Do
                Dim alim As New Alimento
                rigaletta = lettorefile.ReadLine
                If IsNothing(rigaletta) Then Exit Do
                vettore = Split(rigaletta, "*")
                alim.Nome = vettore(0)
                alim.prezzox100g = vettore(1)
                alim.caloriex100g = vettore(2)
                alim.carboidratix100g = vettore(3)
                alim.proteinex100g = vettore(4)
                alim.grassix100g = vettore(5)
                alim.conversione_peso = vettore(6)
                alim.Disponibile = vettore(7)
                alim.Peso_standard = vettore(8)
                alim.IVA = vettore(9)
                alim.Pesocrudo = alim.Peso_standard
                alim.calcola_valori()
                G_listaalimenti.Add(alim)
            Loop
            lettorefile.Close()

       
End Sub

Thanks Sean, i have tried yor second solution, but with same result. Datagridview display All data, but if i update alimenti.txt via FTP the data displayed DONT CHANGE, even, if i DELETE the file from server i take no error ad the data displayed don't change.

G_listaalimenti  is a public BindingList(Of Alimento), alimento is a simple object with various Properties. Here is the code:

Public Class Alimento
    Public Property Nome As String
    Public Property Pesocrudo As Double '***********
    Public Property Pesocotto As Double '***********
    Public Property Carboidrati As Integer '***********
    Public Property Proteine As Integer '***********
    Public Property Grassi As Integer '***********
    Public Property Calorie As Integer '***********
    Public Property Prezzo As Double '***********
    Public Property prezzox100g As Double
    Public Property caloriex100g As Double
    Public Property carboidratix100g As Double
    Public Property proteinex100g As Double
    Public Property grassix100g As Double
    Public Property conversione_peso As Double
    Public Property Disponibile As Boolean = True
    Public Property Peso_standard As Integer
    Public Property IVA As String

    Public Sub calcola_valori() 'tutto calcolato in base a pesocrudo
        If Me.Nome = "TOTALE PIATTO:" Then Exit Sub
        If Me.Nome = "TOTALE ORDINE:" Then Exit Sub
        Me.Pesocotto = Math.Round(Me.Pesocrudo * Me.conversione_peso, 0, MidpointRounding.AwayFromZero)
        Me.prezzox100g = Math.Round(Me.prezzox100g, 2, MidpointRounding.AwayFromZero)
        Me.Prezzo = Math.Round(Me.prezzox100g * Me.Pesocrudo / 100, 2, MidpointRounding.AwayFromZero)
        Me.Calorie = Int(Me.caloriex100g * Me.Pesocrudo / 100)
        Me.Carboidrati = Int(Me.carboidratix100g * Me.Pesocrudo / 100)
        Me.Proteine = Int(Me.proteinex100g * Me.Pesocrudo / 100)
        Me.Grassi = Int(Me.grassix100g * Me.Pesocrudo / 100)
    End Sub
end class

here is the declaration of G_listaalimenti:

 Public G_listaalimenti As New BindingList(Of Alimento)

Here are some lines of  the file "alimenti.txt" :

Anguria*5*65*100*20*45*1*True*50*01*
Farro*2*338*70*15*2*2,5*True*100*01*
Penne*2*356*83*11*0*2*True*100*01*
Pesto*1,3*491*87*67*475*1*True*20*01*
Petto di Pollo grigliato*3,5*97*0*22*1*0,9*True*100*01*
Piselli*1,5*54*75*57*4*0,87*True*30*01*
Riso*3,2*364*793*67*1*2,5*True*80*01*
Riso Basmati*2*364*79*7*1*10*True*80*01*
Trivelle Integrali*2*324*66*13*2*2*True*500

I am using VISUAL STUDIO 2015 with  VB.NET

I have partially solved the problem with:

Session.timeout = 1

in this way, strangely, if I change the page and immediately return to it, I have the updated data despite the fact that the minute has not passed. But shortening the session to one minute creates other problems that we can imagine .... honestly I would prefer a better way than this. Some idea?

Answer 5

User-1330468790 posted

Hi Uruse1980,

 

I notice that you are using componi_Load. Is this similar to Page_Load? Why is it showing a different name?

 

I have tested the codes you provided and successfully update the page with the data from the .txt file. 

Currently I have no idea but have to suspect if you have update the file.txt successfully via FTP.

 

You could refer to the codes below and try the demo from your side to see if it works as from my side.

ReadDataFromFile.aspx

 <form id="form1" runat="server">
         <h3><asp:Label ID="lblutente" runat="server"></asp:Label></h3>
        <div>
            <asp:GridView runat="server" ID="GridView1" AutoGenerateColumns="true">
            </asp:GridView>
        </div>

        <asp:Button ID="postback" runat="server" Text="Post back" />
    </form>

Code behind:

Public G_listaalimenti As New BindingList(Of Alimento)

    Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
        ' If you put codes in Page_Load in Page_Init, then the post back button won't update the data.
    End Sub


    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim nome As String = "Read Data From Text File"

        lblutente.Text = "Ciao " & nome & "!"
        carica_alimenti("01")
        GridView1.DataSource = G_listaalimenti
        GridView1.DataBind()
        Response.Cache.SetCacheability(HttpCacheability.NoCache)
        Response.Cache.SetAllowResponseInBrowserHistory(False)
    End Sub

    Public Sub carica_alimenti(filiale As String)

        G_listaalimenti.Clear()
        Dim vettore() As String
        Dim rigaletta As String = ""
        Dim lettorefile As New StreamReader(Server.MapPath("/Uploads/" & filiale & "/alimenti.txt"))
        Do
            Dim alim As New Alimento
            rigaletta = lettorefile.ReadLine
            If IsNothing(rigaletta) Then Exit Do
            vettore = Split(rigaletta, "*")
            alim.Nome = vettore(0)
            alim.prezzox100g = vettore(1)
            alim.caloriex100g = vettore(2)
            alim.carboidratix100g = vettore(3)
            alim.proteinex100g = vettore(4)
            alim.grassix100g = vettore(5)
            alim.conversione_peso = vettore(6)
            alim.Disponibile = vettore(7)
            alim.Peso_standard = vettore(8)
            alim.IVA = vettore(9)
            alim.Pesocrudo = alim.Peso_standard
            alim.calcola_valori()
            G_listaalimenti.Add(alim)
        Loop
        lettorefile.Close()


    End Sub

alimento.vb

Public Class Alimento
    Public Property Nome As String
    Public Property Pesocrudo As Double '***********
    Public Property Pesocotto As Double '***********
    Public Property Carboidrati As Integer '***********
    Public Property Proteine As Integer '***********
    Public Property Grassi As Integer '***********
    Public Property Calorie As Integer '***********
    Public Property Prezzo As Double '***********
    Public Property prezzox100g As Double
    Public Property caloriex100g As Double
    Public Property carboidratix100g As Double
    Public Property proteinex100g As Double
    Public Property grassix100g As Double
    Public Property conversione_peso As Double
    Public Property Disponibile As Boolean = True
    Public Property Peso_standard As Integer
    Public Property IVA As String

    Public Sub calcola_valori() 'tutto calcolato in base a pesocrudo
        If Me.Nome = "TOTALE PIATTO:" Then Exit Sub
        If Me.Nome = "TOTALE ORDINE:" Then Exit Sub
        Me.Pesocotto = Math.Round(Me.Pesocrudo * Me.conversione_peso, 0, MidpointRounding.AwayFromZero)
        Me.prezzox100g = Math.Round(Me.prezzox100g, 2, MidpointRounding.AwayFromZero)
        Me.Prezzo = Math.Round(Me.prezzox100g * Me.Pesocrudo / 100, 2, MidpointRounding.AwayFromZero)
        Me.Calorie = Int(Me.caloriex100g * Me.Pesocrudo / 100)
        Me.Carboidrati = Int(Me.carboidratix100g * Me.Pesocrudo / 100)
        Me.Proteine = Int(Me.proteinex100g * Me.Pesocrudo / 100)
        Me.Grassi = Int(Me.grassix100g * Me.Pesocrudo / 100)
    End Sub
End Class

Demo:

 

Hope helps.

Best regards,

Sean

Answer 6

User-350763668 posted

Hi Sean, thanks a lot for your time.

"Componi" is the name of my page (www.fooexample/componi.aspx)

When i double click in page form, visual studio 2015 automatically create for me the "componi_load" sub, and NOT "page_load", when i go at INIT event, visual studio create a sub called "componi_init" ecc.......

I have no problem with FTP upload, the file REALLY is updated.

Have you tried to navigate to another page and come back instead of postback?

I noticed that you edit the file locally, if you install the code in real remote webserver and you upgrade file via FTP, i think
probably you have my same problem! Thanks again

Answer 7

User753101303 posted

Maybe a caching issue? I would show the current date/time on the page to see if the value is updated when refreshing the page.

If ok and it still runs when this file is deleted, the only reason I can see is that this file is not needed. I would show perhaps the file size or last modified date on the page to see if it seems consistent with changes done through FTP.

BTW it is uploaded on the web server and you have a single web server?