Asp.net losing values of variables - asp.net

Question

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.

Answer 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");