Reading and Storing Data in Cookies

You can store small pieces of user-specific information in the user's Cookies collection

on the user's local machine, assuming the local browser supports cookies and the user has

not disabled this feature.You can use cookies to hold data for as long as the current

browser window is open, or you can give them an expiration date some time in the

future.The first variety is called an in-memory cookie, because they are never written to

the user's hard drive.The second variety is referred to as a persistent cookie, because

these cookies persist across browser and even machine restarts.

There are several ways to work with cookies in ASP.NET.The simplest uses syntax

very similar to that used for the Application and Session collections:

'write a cookie

Response.Cookies("UserName").Value = UserNameTextBox.Text

'read a cookie

UserNameLabel.Text = Request.Cookies("UserName").Value

In addition, you can give the cookies an expiration date, which will cause them to be

persisted to the user's hard drive.To delete these (and other) cookies, simply set their

expire date to any past date, as shown:

'persist a cookie

Response.Cookies("UserName").Expires =

➥

System.DateTime.Now.AddDays(1) ' persist for 1 day

'delete a cookie

Response.Cookies("UserName").Expires = System.DateTime.Now.AddDays(-1)

Comments

Cookies can be a great place to store small pieces of data that are needed from page to

page.They do not have the overhead of sessions, and they can span multiple user visits

over large time periods.They can also span applications within the same domain (for

example, yahoo.com). Not all users will accept cookies, however. It's best to test for this

by writing a test cookie and attempting to read it back on a subsequent request. Cookies

can store only small amounts of text data, with an upper limit of less than 4KB, which

includes the data and the keys used to extract the data (for example, UserName in the

previous example).