[c#] How to get the cookie value in asp.net website

I am creating a cookie and storing the value of username after succesfull login. How can I access the cookie when the website is opened. If the cookie exist I want to fill the username text box from the cookie value. And how to decrypt the value to get the username. I am doing server side validation by getting the userdetails from the database. I am using vs 2010 with c#

FormsAuthenticationTicket tkt;
string cookiestr;
HttpCookie ck;
tkt = new FormsAuthenticationTicket(1, txtUserName.Value, DateTime.Now,
    DateTime.Now.AddYears(1), chk_Rememberme.Checked, "User Email");
cookiestr = FormsAuthentication.Encrypt(tkt);
ck = new HttpCookie(FormsAuthentication.FormsCookieName, cookiestr);

if (chk_Rememberme.Checked)
{
    ck.Expires = tkt.Expiration;
    ck.Path = FormsAuthentication.FormsCookiePath;
    Response.Cookies.Add(ck);
}

cookie is created with name as .YAFNET_Authentication and content is encrypted

Webconfig:

  <forms name=".YAFNET_Authentication" loginUrl="Home.aspx"
  protection="All" timeout="15000" cookieless="UseCookies"/>

add this function to your global.asax

protected void Application_AuthenticateRequest(Object sender, EventArgs e)
{
    string cookieName = FormsAuthentication.FormsCookieName;
    HttpCookie authCookie = Context.Request.Cookies[cookieName];

    if (authCookie == null)
    {
        return;
    }
    FormsAuthenticationTicket authTicket = null;
    try
    {
        authTicket = FormsAuthentication.Decrypt(authCookie.Value);
    }
    catch
    {
        return;
    }
    if (authTicket == null)
    {
        return;
    }
    string[] roles = authTicket.UserData.Split(new char[] { '|' });
    FormsIdentity id = new FormsIdentity(authTicket);
    GenericPrincipal principal = new GenericPrincipal(id, roles);

    Context.User = principal;
}

then you can use HttpContext.Current.User.Identity.Name to get username. hope it helps

HttpCookie cook = new HttpCookie("testcook");
cook = Request.Cookies["CookName"];
if (cook != null)
{
    lbl_cookie_value.Text = cook.Value;
}
else
{
    lbl_cookie_value.Text = "Empty value";
}

Reference Click here

FormsAuthentication.Decrypt takes the actual value of the cookie, not the name of it. You can get the cookie value like

HttpContext.Current.Request.Cookies[FormsAuthentication.FormsCookieName].Value;

and decrypt that.