How to delete cookies on an ASP.NET website

In my website when the user clicks on the "Logout" button, the Logout.aspx page loads with code Session.Clear().

In ASP.NET/C#, does this clear all cookies? Or is there any other code that needs to be added to remove all of the cookies of my website?

Try something like that:

if (Request.Cookies["userId"] != null)
{
    Response.Cookies["userId"].Expires = DateTime.Now.AddDays(-1);   
}

But it also makes sense to use

Session.Abandon();

besides in many scenarios.

No, Cookies can be cleaned only by setting the Expiry date for each of them.

if (Request.Cookies["UserSettings"] != null)
{
    HttpCookie myCookie = new HttpCookie("UserSettings");
    myCookie.Expires = DateTime.Now.AddDays(-1d);
    Response.Cookies.Add(myCookie);
}

At the moment of Session.Clear():

• All the key-value pairs from Session collection are removed. Session_End event is not happen.

If you use this method during logout, you should also use the Session.Abandon method to Session_End event:

• Cookie with Session ID (if your application uses cookies for session id store, which is by default) is deleted

This is what I use:

    private void ExpireAllCookies()
    {
        if (HttpContext.Current != null)
        {
            int cookieCount = HttpContext.Current.Request.Cookies.Count;
            for (var i = 0; i < cookieCount; i++)
            {
                var cookie = HttpContext.Current.Request.Cookies[i];
                if (cookie != null)
                {
                    var expiredCookie = new HttpCookie(cookie.Name) {
                        Expires = DateTime.Now.AddDays(-1),
                        Domain = cookie.Domain
                    };
                    HttpContext.Current.Response.Cookies.Add(expiredCookie); // overwrite it
                }
            }

            // clear cookies server side
            HttpContext.Current.Request.Cookies.Clear();
        }
    }

Unfortunately, for me, setting "Expires" did not always work. The cookie was unaffected.

This code did work for me:

HttpContext.Current.Session.Abandon();
HttpContext.Current.Response.Cookies.Add(new HttpCookie("ASP.NET_SessionId", ""));

where "ASP.NET_SessionId" is the name of the cookie. This does not really delete the cookie, but overrides it with a blank cookie, which was close enough for me.

I just want to point out that the Session ID cookie is not removed when using Session.Abandon as others said.

> When you abandon a session, the session ID cookie is not removed from > the browser of the user. Therefore, as soon as the session has been > abandoned, any new requests to the same application will use the same > session ID but will have a new session state instance. At the same > time, if the user opens another application within the same DNS > domain, the user will not lose their session state after the Abandon > method is called from one application. > > Sometimes, you may not want to reuse the session ID. If you do and if > you understand the ramifications of not reusing the session ID, use > the following code example to abandon a session and to clear the > session ID cookie: > > Session.Abandon(); > Response.Cookies.Add(new HttpCookie("ASP.NET_SessionId", "")); > > This code example clears the session state from the server and sets > the session state cookie to null. The null value effectively clears > the cookie from the browser.

http://support.microsoft.com/kb/899918

It is 2018 now, so in ASP.NET Core, there is a straight forward built in function. To delete a cookie try this code:

if(Request.Cookies["aa"] != null)
{
    Response.Cookies.Delete("aa");
}
return View();

You should never store password as a cookie. To delete a cookie, you really just need to modify and expire it. You can't really delete it, ie, remove it from the user's disk.

Here is a sample:

HttpCookie aCookie;
    string cookieName;
    int limit = Request.Cookies.Count;
    for (int i=0; i<limit; i++)
    {
        cookieName = Request.Cookies[i].Name;
        aCookie = new HttpCookie(cookieName);
        aCookie.Expires = DateTime.Now.AddDays(-1); // make it expire yesterday
        Response.Cookies.Add(aCookie); // overwrite it
    }

Taking the OP's Question title as deleting all cookies - "Delete Cookies in website"

I came across code from Dave Domagala on the web somewhere. I edited Dave's to allow for Google Analytics cookies too - which looped through all cookies found on the website and deleted them all. (From a developer angle - updating new code into an existing site, is a nice touch to avoid problems with users revisiting the site).

I use the below code in tandem with reading the cookies first, holding any required data - then resetting the cookies after washing everything clean with the below loop.

The code:

int limit = Request.Cookies.Count; //Get the number of cookies and 
                                   //use that as the limit.
HttpCookie aCookie;   //Instantiate a cookie placeholder
string cookieName;   

//Loop through the cookies
for(int i = 0; i < limit; i++)
{
 cookieName = Request.Cookies[i].Name;    //get the name of the current cookie
 aCookie = new HttpCookie(cookieName);    //create a new cookie with the same
                                          // name as the one you're deleting
 aCookie.Value = "";    //set a blank value to the cookie 
 aCookie.Expires = DateTime.Now.AddDays(-1);    //Setting the expiration date
                                                //in the past deletes the cookie

 Response.Cookies.Add(aCookie);    //Set the cookie to delete it.
}

Addition: If You Use Google Analytics

The above loop/delete will delete ALL cookies for the site, so if you use Google Analytics - it would probably be useful to hold onto the __utmz cookie as this one keeps track of where the visitor came from, what search engine was used, what link was clicked on, what keyword was used, and where they were in the world when your website was accessed.

So to keep it, wrap a simple if statement once the cookie name is known:

... 
aCookie = new HttpCookie(cookieName);    
if (aCookie.Name != "__utmz")
{
    aCookie.Value = "";    //set a blank value to the cookie 
    aCookie.Expires = DateTime.Now.AddDays(-1);   

    HttpContext.Current.Response.Cookies.Add(aCookie);    
}

Though this is an old thread, i thought if someone is still searching for solution in the future.

HttpCookie mycookie = new HttpCookie("aa");
mycookie.Expires = DateTime.Now.AddDays(-1d);
Response.Cookies.Add(mycookie1);

Thats what did the trick for me.

Response.Cookies["UserSettings"].Expires = DateTime.Now.AddDays(-1)

You have to set the expiration date to delete cookies

Request.Cookies[yourCookie]?.Expires.Equals(DateTime.Now.AddYears(-1));

This won't throw an exception if the cookie doesn't exist.

I strongly preferer this if anyone like it.

string COOKIE_NAME = "COOCKIE NAME"

if (HttpContext.Request.Cookies.AllKeys.Contains(COOKIE_NAME))
        {
            HttpCookie Cookie = HttpContext.Request.Cookies[COOKIE_NAME];
            engagementIdCookie.Expires = DateTime.Now.AddDays(-1);
            Response.Cookies.Add(Cookie);
        }