PostBack and session values. Why after button is clicked and session created postback still show null

Question

protected void Page_Load(object sender, EventArgs e)
{

    if (!IsPostBack)
    {
        lblPostBack.Text = " Text created first time";
    }
    else
    {
        if (Session["Counter"] == null)
        {
            lblPostBack.Text = "PostBack x however strange becasue if is postback it's mean somebody clicked button and session value has been created";

        }
        else
        {
            lblPostBack.Text = "PostBack x should be count here";
        }
    }
}
protected void cmd_Click(object sender, EventArgs e)
{
    int _counter;
    if (Session["Counter"] == null)
    {
        _counter = 1;

    }
    else
    {
        _counter = (int)Session["Counter"] + 1;
    }
    Session["Counter"] = _counter;
    lblPostBack.Text += "Counter: " + _counter.ToString();
}

Answer 1

Ok it works, just FF mess up

Answer 2

I have added following method and works fine.

private int _counter;

protected void Page_Load(object sender, EventArgs e)
{
(...)

protected void Page_PreRender(Object sender, EventArgs e) { Session["Counter"] = _counter; }

Answer 3

Assuming this is ASP.NET: It's because the Click event on your button fires after the Load event on your page, so the session has not been set.

MSDN on the page lifecycle might be good reading - the button click is a "postback event" in the table in that document.

If I've got the wrong end of the stick, please explain what messages you get after the button clicks, and what you were expecting. Some framework and language tags on the question might not go amiss, either.