When to use Request.Cookies over Response.Cookies?

Do I use response when at a page event (e.g. load) as this is a response from ASP.NET, and request when pressing a button as this is a response going to ASP.NET for processing? Or is there more to it?

They are 2 different things, one SAVES [Response], the other READS [Request]

in a Cookie (informatics speaking) :) you save a small file for a period of time that contains an object of the type string

in the .NET framework you save a cookie doing:

HttpCookie myCookie = new HttpCookie("MyTestCookie");
DateTime now = DateTime.Now;

// Set the cookie value.
myCookie.Value = now.ToString();
// Set the cookie expiration date.
myCookie.Expires = now.AddMinutes(1);

// Add the cookie.
Response.Cookies.Add(myCookie);

Response.Write("<p> The cookie has been written.");

You wrote a cookie that will be available for one minute... normally we do now.AddMonth(1) so you can save a cookie for one entire month.

To retrieve a cookie, you use the Request (you are Requesting), like:

HttpCookie myCookie = Request.Cookies["MyTestCookie"];

// Read the cookie information and display it.
if (myCookie != null)
   Response.Write("<p>"+ myCookie.Name + "<p>"+ myCookie.Value);
else
   Response.Write("not found");

Remember:

To Delete a Cookie, there is no direct code, the trick is to Save the same Cookie Name with an Expiration date that already passed, for example, now.AddMinutes(-1)

this will delete the cookie.

As you can see, every time that the time of life of the cookie expires, that file is deleted from the system automatically.

In a web application the request is what comes from the browser and the response is what the server sends back. When validating cookies or cookie data from the browser you should use the Request.Cookies. When you are constructing cookies to be sent to the browser you need to add them to Response.Cookies.

When writing a cookie, use Response but reading may depend on your situation. Normally, you read from Request but if your application is attempting to get a cookie that has just been written or updated and the round trip to the browser has not occured, you may need to read it form Response.

I have been using this pattern for a while and it works well for me.

public void WriteCookie(string name, string value)
{
    var cookie = new HttpCookie(name, value);
    HttpContext.Current.Response.Cookies.Set(cookie);
}


public string ReadCookie(string name)
{
    if (HttpContext.Current.Response.Cookies.AllKeys.Contains(name))
    {
        var cookie = HttpContext.Current.Response.Cookies[name];
        return cookie.Value;
    }

    if (HttpContext.Current.Request.Cookies.AllKeys.Contains(name))
    {
        var cookie = HttpContext.Current.Request.Cookies[name];
        return cookie.Value;
    }

    return null;
}

The cookies comes from the browser in the Request.Cookies collection. That is where you read the cookies that was sent.

To send cookies back to the browser you put them in the Response.Cookies collection.

If you want to delete a cookie, you have to tell the browser to remove it by sending the cookie with an expiration date that has passed. The browser is using the local time of the client computer so if you are using the server time to create a date, be sure to subtract at least one day to be sure that it has actually passed in the clients local time.

When i create or update a cookie in .NET i normally do it to both the request and response cookie collection. That way you can be sure if you try to read the cookie further down the page request sequence it will have the correct information.

Andrew's Code gave an error in "AllKeys.Contains" Method. So I corrected a little..

public void WriteCookie(string strCookieName, string strCookieValue)
    {
        var hcCookie = new HttpCookie(strCookieName, strCookieValue);
        HttpContext.Current.Response.Cookies.Set(hcCookie);
    }


    public string ReadCookie(string strCookieName)
    {    
        foreach (string strCookie in HttpContext.Current.Response.Cookies.AllKeys)
        {
            if (strCookie == strCookieName)
            {
                return HttpContext.Current.Response.Cookies[strCookie].Value;
            }
        }         

        foreach (string strCookie in HttpContext.Current.Request.Cookies.AllKeys)
        {
            if (strCookie == strCookieName)
            {
                return HttpContext.Current.Request.Cookies[strCookie].Value;
            }
        }

        return null;
    }