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Handling cookies in ASP .NET:-
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How to create a cookie, how
to get the value stored in a cookie, set the lifetime, path and domain for a cookie,
edit a cookie, delete a cookie,
remove subkeys from a cookie...
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Here's a tutorial that shows
you how to use cookies in ASP .NET. I'm not going to explain the role of cookies
in
web applications or cover
any other theoretical aspect of cookies. There are many (similar) ways to handle
cookies in ASP .NET. I'm only
going to show you one of the ways, my way. Oh, and we're going to use C#,
although the code can be adapted
to Visual Basic .NET easily.
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How to create a cookie.
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Here's a new cookie named
cakes.
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HttpCookie myCookie = new HttpCookie("cakes");
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We created the cookie but
there are no keys with values in it, so for now it's useless. So let's add some:
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myCookie.Values.Add("muffin",
"chocolate");
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myCookie.Values.Add("babka",
"cinnamon");
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We also need to add the cookie
to the cookie collection (consider it a cookie jar
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):
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Response.Cookies.Add(myCookie);
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How to get the value stored
in a cookie.
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Here's how to get the keys
and values stored in a cookie:
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Response.Write(myCookie.Value.ToString());
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The output to using this with
the previous created cookie is this: "muffin=chocolate&babka=cinnamon".
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However, most of the time
you'll want to get the value stored at a specific key. If we want to find the
value
stored at our babka key, we
use this:
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Response.Write(myCookie["babka"].ToString());
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Set the lifetime for a cookie.
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You can easily set the time
when a cookie expires. We'll set the Expires property of myCookie to the current
time + 12 hours:
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myCookie.Expires = DateTime.Now.AddHours(12);
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This cookie will expire in
twelve hours starting now. You could as well make it expire after a week:
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myCookie.Expires = DateTime.Now.AddDays(7);
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Also note that if you don't set
a cookie's expiration date & time a transient cookie will be created - a cookie
which only exists in the current
browser instance. So if you want the cookie to be stored as a file you need to
set this property.
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Setting the cookie's path.
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Sometimes you'll want to set
a path for a cookie so that it will be available only for that path in your website
(ex.: www.dotnetsparkles.com/Careers).
You can set a cookie's path with the Path property:
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myCookie.Path = "/forums";
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Perhaps instead of using http://www.dotnetsparkles.com/Careers
path style to your forums, you would use a
subdomain like http://Careers.dotnetsparkles.com.
The Domain property should do it:
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myCookie.Domain = "forums.geekpedia.com";
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How to edit a cookie.
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You don't actually edit a
cookie, you simply overwrite it by creating a new cookie with the same key(s).
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How to destroy / delete a
cookie.
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There's no method called Delete
which deletes the cookie you want. What you can do if you have to get rid of
a cookie is to set its expiration
date to a date that has already passed, for example a day earlier. This way the
browser will destroy it.
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myCookie.Expires = DateTime.Now.AddDays(-1);
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How to remove a subkey from
a cookie.
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This is one of the problems
I encountered with cookies. Fortunately I found an answer on MSDN. You can use
the Remove method:
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myCookie.Values.Remove("babka");
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However, you don't usually
remove a subkey immediatly after creating it, so first we need to retrieve the
cookie, remove the subkey
and then add it back to the Cookies collection:
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// Get the cookie from the
collection (jar)
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myCookie = Request.Cookies["cakes"];
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// Remove the key 'babka'
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myCookie.Values.Remove("babka");
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// Add the cookie back to
the collection (jar)
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Response.Cookies.Add(myCookie);
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// See what's in the cookie
now
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Response.Write(myCookie.Values.ToString());
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Of course I suppose you used
the code we created earlier (the one with the chocolate muffin and the
cinnamon babka), therefore
if you test the code now you'll see the result is 'muffin=chocolate' - we got
rid of
the babka!
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