Asp.net losing values of variables

I am trying to write my first WebApplication in ASP.NET. Here is my code:

Public Class WebForm2
Inherits System.Web.UI.Page
Public n As Integer
Public zetony As Integer
Public liczba As Boolean
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

End Sub
Private Function TextBox1_Validate(Cancel As Boolean)
    If Not IsNumeric(TextBox1.Text) Then
        MsgBox("Prosze podaj liczbe dobry uzytkowniku :)", vbInformation)
        Cancel = True
    Else : Cancel = False
    End If
    Return Cancel
End Function
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    liczba = TextBox1_Validate(liczba)
    If (liczba = False) Then
        n = Convert.ToInt32(TextBox1.Text)
        Label2.Text = n
    End If
End Sub
Protected Sub graj()
    Label2.Text = n
End Sub
Protected Sub Image1_Click(sender As Object, e As ImageClickEventArgs) Handles ImageButton1.Click
    If zetony < 2 Then
        n -= 1
        ImageButton1.ImageUrl = "red_coin.gif"
        zetony += 1
    End If
End Sub

Protected Sub Image2_Click(sender As Object, e As ImageClickEventArgs) Handles ImageButton2.Click
    If zetony < 2 Then
        n -= 1
        ImageButton2.ImageUrl = "red_coin.gif"
        zetony += 1
    End If
End Sub

Protected Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    graj()
End Sub
End Class

My problem is that, only on Button1_Click I got proper value. When I try to call Sub graj() value of n is alwayes 0.

Answers:

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Method 1

HTTP is stateless. This means that for every request a new instance of the class WebForm2 gets created. So if you set the value of n inside Button1_Click it will not be preserverd when you access it from Button2_Click since it’s a different instance.

To save your data across requests there are several possibilities, to name a few:

• Save it in a database
• Save it in the Application-object (this is shared across all users:

  // setting the value
  HttpContext.Current.Application("n") = "somevalue";
  
  // Getting the value
  string test = HttpContext.Current.Application("n");

• Save it in the session-state (this is shared across all requests for one user):

  // setting the value
  HttpContext.Current.Session("n") = "somevalue";
  
  // Getting the value
  string test = HttpContext.Current.Session("n");

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0