Cookies ch6 p222-224

Alanrf · January 25th, 2010, 08:48 AM

Hi Imar,

Following the code for inserting and defining cookies, (which, of course does work OK), and in the process of testing my own competence I made a typo in defining the values in the DDL in MasterPage/Master, which should have included the line:

Code:

<div id="SideBar">Select a Theme
        <asp:DropDownList ID="lstPreferredTheme" runat="server" AutoPostBack="True" 
          onselectedindexchanged="lstPreferredTheme_SelectedIndexChanged">
          ...
          <asp:ListItem>DarkGrey</asp:ListItem>            
          ...
        </asp:DropDownList>
</div>

Being less than careful in entering the line I inadvertently entered

Code:

 ...
          <asp:ListItem>Dark Grey</asp:ListItem>            
...

with the embedded space. Stupid, yes! Careless, yes! However, as this forced me into error mode as the 'Dark Grey' theme did not exist I had to remove the cookie to continue. I achieved this by drilling into
%userprofile%\AppData\Roaming\Microsoft\Windows\Co okies\Low and deleting the specific cookie. This was more of a chore than an inconvenience, but later I did further checking and found that if I changed the code in MasterPage.master.cs from

Code:

protected void lstPreferredTheme_SelectedIndexChanged(object sender, EventArgs e)
    {
     ...
      preferredTheme.Expires = DateTime.Now.AddMonths(3);
     ...
    }

to

Code:

...
      preferredTheme.Expires = DateTime.Now.AddDays(-1);
...

I could clear the cookie instantly.

I wonder if it may be worth adding some clarification in future editions to provide a more elegant method of killing an invalid, or incorrect cookie. For all of the usual reasons I would have been loathe to clear all cookies, (something of an overkill in this case), and I have no real issues with drilling down, but perhaps the programmatic method is both 'safer' and perhaps more elegant.

There again, I suspect that not many people will run into this issue anyway.

Imar · January 25th, 2010, 03:55 PM

Yes, good suggestion. I am indeed doing something like this in my new book, based on some earlier reports.

One solution is to use a Try / Catch block where you try to set the theme based on the cookie, and delete the cookie when the code crashes somehow. Using the Expires property is indeed the way to remove the cookie.

Cheers,

Imar