Access session variable of one website in another website in ASP.Net

hi

I have two website

1-www.firstsite.com

2-www.Secondsite.com

in www.Secondsite.com I used session to save data:

below are code:

show.aspx in(www.secondsite.com)

        if (Session["UserData"] != null)
            {
                UserData userData = Session["UserData"] as UserData;
                if (userData != null)
                {
                    Txtname.Text = userData.Name;
                    TxtMob.Text = userData.Mobile;
                    txttell.Text = userData.Tell;
                    TxtcodeU.Text = userData.PostCode;
                    Txtaddu.Text = userData.Address;
                    TxtEmail.Text = userData.Email;
                }
            }

now in verify.aspx page in www.firstsite.aspx is button that when users click on this button it will go to www.secondsite.com/show.aspx page :

    protected void LBback_Click(object sender, EventArgs e)
    {
        Response.Redirect("www.secondsite.com/show.aspx");
    }

problem is that when users click button it go to secondsite.com/show.aspx but it doesn't show session's data that I define:

     if (Session["UserData"] != null)
            {
                UserData userData = Session["UserData"] as UserData;
                if (userData != null)
                {
                    Txtname.Text = userData.Name;
                    TxtMob.Text = userData.Mobile;
                    txttell.Text = userData.Tell;
                    TxtcodeU.Text = userData.PostCode;
                    Txtaddu.Text = userData.Address;
                    TxtEmail.Text = userData.Email;
                }
            }

where is problem

best regards

neda