Persistant variables in ASP.NET

How do you make a variable retain it's value between client-server trips?

Take for instance the code below:

Code:

---

    Dim sText As String

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        sText &= "x"
        Label1.Text = sText
    End Sub

---

Looking at it you'd expect that every time you pressed the button, Label1 would gain one more x on the end. It doesn't work however, because each time it forgets the value of sText. (incidentally it remembers Label1.Text, but that's not my problem here...I'm interested in variables not objects' properties).

I had a look in the msdn docs and it goes on about some state bag or something but it didn't make much sense to me at the time.

So...anyone help me out here...amend my example or explain it to me a bit better? Ta :)