Who does not like cookies?
As I was doing some odd exploration of an older ASP application I decided to do some experimentation with cookies. As with most of my posts I try to drop things back significantly allowing for some basic examples. Cookies are a way for a web application to store specific information. Cookies are small text files that are stored on a client machine and are contained in the
Response and
Request traffic between a client and host computer. Web applications can read cookies whenever a user visits the site. Information such as user preferences could be stored in a cookie.
Within .NET there the
HttpCookie Class is used for dealing with cookie information. Basic dealing with cookies is a lot easier than it may initially sound. I was able to put together a sample application that stores a textbox, validated textbox and calendar date (cookies store strings) in a cookie in only a few minutes.
Start a new ASP.NET Web Application from within
BDS2006. On the default design form place a two text boxes, a calendar control, a RegularExpressionValidator and three buttons. I also placed some labels for identification.
Set the properties for RegularExpression1 as follows:
// This checks for a proper email address
ValidationExpression:= ‘\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*’;
ControlToValidate:= txtEmail;
ErrorMessage:= ‘Invalid Email’;
The following is the code behind the page (For maintenance, I’d use constants for the value and cookie names):
procedure TWebForm1.Page_Load(sender: System.Object; e: System.EventArgs);
begin
// The calendar defaults to a selected date of 01/01/0001
if Calendar1.SelectedDate = DateTime.Parse('01/01/0001') then
Calendar1.SelectedDate:= DateTime.Now;
end;
procedure TWebForm1.btnClear_Click(sender: System.Object; e: System.EventArgs);
var
hc: HttpCookie;
begin
if Request.Cookies['MySite'] <> nil then
begin
hc:= Request.Cookies['MySite'];
// This method may work, however the proper way to clear a cookie
// is to set the cookie to have a prior expiration date
// hc.Values.Clear;
// Response.Cookies.Add(hc);
// Calendar1.SelectedDate:= DateTime.Now;
hc.Expires:= DateTime.Now.AddDays(-100);
txtName.Text:='';
txtEmail.Text:= '';
Calendar1.SelectedDate:= DateTime.Now;
end;
end;
procedure TWebForm1.btnRead_Click(sender: System.Object; e: System.EventArgs);
var
hc: HttpCookie;
begin
if Request.Cookies['MySite'] <> nil then
begin
txtEmail.Text:= Request.Cookies['MySite'].Values['email'];
txtName.Text:= Request.Cookies['MySite'].Values['name'];
Calendar1.SelectedDate:= DateTime.Parse(Request.Cookies['MySite'].Values['date']);
end
else
begin
txtEmail.Text:= '';
txtName.Text:= '';
Calendar1.SelectedDate:= DateTime.Now;
end;
end;
procedure TWebForm1.btnWrite_Click(sender: System.Object; e: System.EventArgs);
var
hc: HttpCookie;
begin
if RegularExpressionValidator1.IsValid then
begin
hc:= HttpCookie.Create('MySite');
hc.Values['name']:= txtName.Text;
hc.Values['email']:= txtEmail.Text;
hc.Values['date']:= Calendar1.SelectedDate.ToShortDateString;
// Expire cookie in 1hour. Always set an expiration
// if you do not set an expiration date the cookie is not
// stored; it will be treated as a session variable
// DateTime.MaxValue will make it last forever
hc.Expires:= DateTime.Now.AddHours(1);
Response.Cookies.Add(hc);
end;
end;
For some more information take a look at
ASP.NET Cookies Overview on MSDN. Another valuable link is
How to Share Session State Between Classic ASP and ASP.NET.
Labels: .NET, ASP.NET, Code, Delphi
AddrMon
October 2005
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