What is the best practice for updating a cookie that was set on a previous request in ASP.NET?

Question

Here is the scenario. A cookie with the key "MyCookie" has been set on a previous request. I can access it via HttpContext.Request.Cookies.Get("MyCookie"). I want to perform an update such as adding another value to the Cookie Values collection, but I'm not 100% sure I am doing it right.

Am I doing this correctly in the following example?

   public static void UpdateCookie(HttpContext context, string cookieName, Action<HttpCookie> updateCookie){
        var cookie = context.Request.Cookies.Get(cookieName);
        updateCookie(cookie);
        context.Response.Cookies.Set(cookie);
   }

Answer 1

To update a cookie, you need only to set the cookie again using the new values. Note that you must include all of the data you want to retain, as the new cookie will replace the previously set cookie. I'm going to assume that your implementation of updateCookie() does just that.

Otherwise, your general premise is correct. Here's an implementation I've used many times to do just that. (Note: _page is a reference to the current Page):

/// <summary> 
/// Update the cookie, with expiration time a given amount of time from now.
/// </summary>
public void UpdateCookie(List<KeyValuePair<string, string>> cookieItems, TimeSpan? cookieLife)
{
    HttpCookie cookie = _page.Request.Cookies[COOKIE_NAME] ?? new HttpCookie(COOKIE_NAME);

    foreach (KeyValuePair<string, string> cookieItem in cookieItems)
    {
        cookie.Values[cookieItem.Key] = cookieItem.Value;
    }

    if (cookieLife.HasValue)
    {
        cookie.Expires = DateTime.Now.Add(cookieLife.Value);
    } 
    _page.Response.Cookies.Set(cookie);
}