C# - Cookies Are Always Null After Postback?

i am trying to maintain some data into cookies but after postback if i check the value of the cookies in pageload the value is always null

this is how i set and get the cookies

private static string GetCookie(string name)
{
return HttpContext.Current.Response != null ? HttpContext.Current.Response.Cookies[name].Value : string.Empty;
}
private static void SetCookie(string name, string value)
{
HttpContext.Current.Response.Cookies[name].Value = value;
HttpContext.Current.Response.Cookies[name].Expires = DateTime.Now.AddDays(ExpireTimeInDays);
}