CIS 451: Cookies Dr. Ralph D. Westfall February, 2009

Problem server mostly tracks requests for files very efficient for high volume of users memory doesn't know who is asking for files even if from link on file in same web site to help server, could send identification identification needs to associated with all files requested by same user of application use HTML "hidden fields" in later pages?

Possible Solutions password login (+ hidden fields) advantage: highest security disadvantage: extra work for customer automated identification (+ hidden) could generate a random # to ID customer advantage: no extra work for customer disadvantage: only good for one session can' track repeat visits by same person

Another Solution: Cookies information stored in file on client computer National Semiconductor cookies policycookies policy advantages user only needs to enter data one time data "persists," so it is available in later sessions disadvantages some users won't allow cookies (very few?) cookies can be removed from user's computer expire, replaced by newer ones, or cleared by user

Cookies cookies have names a cookie can have multiple values cookie data accessed by the cookie's name (and by the keys if more than one value) cookies are part of both the Request and Response ASP intrinsic objects created by Response.Cookies methods stored in Request.Cookies "collection"

Working with Cookies creating Response.Cookies("cookie")("key") = "value" 'substitute "literals" or string variables for 'items within " " 'note similarities to selection of multiple 'items in a ListBox on HTML or.NET form deleting Response.Cache.SetExpires _ 'line continuation (DateTime.Now.AddDays(-5))'positive or negative 'negative value deletes on client 'but session still has data

Using QueryString in an aspx File can create the same effect sending from an aspx file as from a html file Response.Redirect("rsp.aspx?Name=" & _ this.txtName.Text & "&LastName=" & _ this.txtLastName.Text) values are URL encoded and visible in browser address of destination page one way to migrate from html to aspx

Working with Cookies - 2 accessing strValue = Request.Cookies("cookie")("key") 'note that data is accessed from Request object counting cookies intCount = Request.Cookies.Count + 1 '0 based: need to add 1 to get actual #

Viewing Cookies install Web Developer add-on for Firefox Cookies>View Cookie Information

Cookie Exercise create a web project in VB.NET add one TextBox and a Button to the Default.aspx form add another form named CookieRead.aspx and add a Label to it

Cookie Exercise - 2 double-click on each form to create the aspx.vb code-behind files or right-click on the file names in Solution Explorer>View Code download cookiewrite.aspx and cookieread.aspx from Code Samplescookiewrite.aspx cookieread.aspx use the code examples to get the two pages to run

Cookie Exercise - 3 make enhancements add some more input fields to Default.aspx and modify CookieRead.aspx to output these new fields add a Button to reset TextBoxes to blanks rather than reloading cookie values add Button to 2 nd page to delete cookie