Cookies in ASP.NET 4.0

Cookies are one of the State Management techniques, so that we can store information for later use. Cookies are small files that are created in the web browser's memory (if they're temporary) or on the client's hard drive (if they're permanent).

One advantage of cookies is that they work transparently without the user being aware that information needs to be stored. They also can be easily used by any page in your application and even be retained between visits, which allows for truly long-term storage.

They suffer from some of the same drawbacks namely, they're limited to simple string information, and they're easily accessible and readable if the user finds and opens the corresponding file. These factors make them a poor choice for complex or private information or large amounts of data.

Also Some users disable cookies on their browsers, which will cause problems for web applications that require them. Also, users might manually delete the cookie files stored on their hard drives. But for the most part, cookies are widely adopted and used extensively on many websites.

Before we can use cookies, we should import the System.Net namespace so we can easily work with the appropriate types:

using System.Net;

Cookies are fairly easy to use. Both the Request and Response objects (which are provided through Page properties) provide a Cookies collection. The important trick to remember is that we retrieve cookies from the Request object, and we set cookies using the Response object.

To set a cookie, just create a new HttpCookie object. we can then fill it with string information
and attach it to the current web response:

 // Create the cookie object.
 HttpCookie cookie = new HttpCookie("CookieName");
 // Set a value in it.
 cookie["Language"] = "Tamil";
 // Add another value.
 cookie["Country"] = "India";
 // Add it to the current web response.
 Response.Cookies.Add(cookie);

A cookie added in this way will persist until the user closes the browser and will be sent with every request. To create a longer-lived cookie, you can set an expiration date:

// This cookie lives for one year.
cookie.Expires = DateTime.Now.AddYears(1);

we retrieve cookies by cookie name using the Request.Cookies collection:

 HttpCookie cookie = Request.Cookies["CookieName"];
 // Check to see whether a cookie was found with this name.
 string language;
 if (cookie != null)
 {
     language = cookie["Language"];
 }

The only way to remove a cookie is by replacing it with a cookie that has an expiration date that has already passed. This code demonstrates the technique:

HttpCookie cookie = new HttpCookie("Preferences");
cookie.Expires = DateTime.Now.AddDays(-1);
Response.Cookies.Add(cookie);

A Cookie Example

I have attached an Example that shows how to Set and Reset Cookies. To try this example, begin by running the page, entering a value, and clicking the Set Cookie button. Then, close the browser (or click refresh button), and request the page again. The second time, the page will find the cookie, read the value, and display.

Set Cookie!

Refresh the Page Again!