Cookies are small bit of text that is stored by web servers on to user machine.
It contains user related information, example if we want to store record of user
who had logged on to the site from specified machine then we can store cookie in
that machine.
Writing Cookie
Here is the code which demonstrates how to write cookie.
Response.Cookies["username"].Value =
"Mac";
Response.Cookies["userName"].Expires =
DateTime.Now.AddDays(1);
First line sets the value and second line of the
code above sets the expiry date of the cookie. Here it is one day, which can be
modified when needed.
Reading Cookie
Here is the code which demonstrates how to read cookie.
if
(Request.Cookies["username"] !=
null)
lblUsername.Text = "User Name: "+Request.Cookies["username"].Value;
In the code above first we are checking whether
cookie exist to avoid error raised if cookie does not exist.
After checking for cookie existance we read it:
Request.Cookies["username"].Value
Here is an example to demonstrate the use of
cookies
Design source for above screen shot
<body>
<form
id="form1"
runat="server">
<p>
<asp:Button
ID="btnCookie0"
runat="server"
style="position:absolute"
onclick="btnCookie_Click"
Text="Cookie"
/>
<asp:Button
ID="btnGreen"
runat="server"
style="position:absolute;
top: 51px;
left: 169px;" onclick="btnGreen_Click"
Text="Green"
/>
</p>
<asp:Button
ID="btnDefault"
runat="server"
style="position:absolute;
top: 50px;
left: 91px;" onclick="btnDefault_Click"
Text="Default"
/>
<p>
</p>
<p>
<asp:Label
ID="lblPrevLogin"
runat="server"
style="position:absolute;
top: 229px;
left: 33px;"></asp:Label>
<asp:Label
ID="lblCounter"
runat="server"
style="position:absolute;
top: 185px;
left: 33px;"></asp:Label>
<asp:Label
ID="lblLastvisit"
runat="server"
style="position:absolute;
top: 147px;
left: 33px;"></asp:Label>
<asp:Label
ID="lblUsername"
runat="server"
style="position:absolute;
top: 116px;
left: 33px;"></asp:Label>
</p>
<asp:Button
ID="btnYellow"
runat="server"
style="position:absolute;
top: 52px;
left: 260px;" onclick="btnYellow_Click"
Text="Yellow"
/>
</form>
</body>
ASP.NET code
protected
void Page_Load(object
sender, EventArgs e)
{
//creating counter to check how
many times user has visited page
int counter;
if (Request.Cookies["counter"] == null)
counter = 0;
else
{
counter = int.Parse(Request.Cookies["counter"].Value);
}
counter++;
//writing counter cookie
Response.Cookies["counter"].Value
= counter.ToString();
Response.Cookies["counter"].Expires =
DateTime.Now.AddDays(1);
//storing last visit
information in cookie
Response.Cookies["lastvisit"].Value =
lblPrevLogin.Text;
//storing user name in cookie
Response.Cookies["username"].Value =
"Mac";
Response.Cookies["userName"].Expires =
DateTime.Now.AddDays(1);
//writing last visited details
Response.Cookies["lastvisit"].Value =
DateTime.Now.ToString();
Response.Cookies["lastvisit"].Expires
= DateTime.Now.AddDays(1);
//checking for counter cookie
and displaying the counter in label
if (Request.Cookies["counter"] != null)
lblCounter.Text = "Counter: " +
Request.Cookies["counter"].Value;
//checking lastvisit cookie and
displaying it in label
if (Request.Cookies["lastvisit"] != null)
lblPrevLogin.Text =
Request.Cookies["lastvisit"].Value;
//checking for color cookie set by the
user and changing the backcolor of //lable accordingly.
if (Request.Cookies["color"]
!= null)
{
if (Request.Cookies["color"].Value ==
"Red")
lblPrevLogin.BackColor = System.Drawing.Color.Red;
else if
(Request.Cookies["color"].Value ==
"Green")
lblPrevLogin.BackColor = System.Drawing.Color.Green;
else if
(Request.Cookies["color"].Value ==
"Yellow")
lblPrevLogin.BackColor = System.Drawing.Color.Yellow;
}
}
protected void
btnCookie_Click(object sender,
EventArgs e)
{
//displaying user name and
lastvisit information of user
if (Request.Cookies["username"] != null)
lblUsername.Text = "User Name: "+Request.Cookies["username"].Value;
if (Request.Cookies["lastvisit"] != null)
lblLastvisit.Text = "Last Visited: "+Request.Cookies["lastvisit"].Value;
}
//modifing color cookie and and
changing backcolor of label accorgind to //button click
protected void
btnDefault_Click(object sender,
EventArgs e)
{
Response.Cookies["color"].Value =
"Red";
Response.Cookies["color"].Expires =
DateTime.Now.AddDays(1);
lblPrevLogin.BackColor = System.Drawing.Color.Red;
}
protected void
btnGreen_Click(object sender,
EventArgs e)
{
Response.Cookies["color"].Value =
"Green";
Response.Cookies["color"].Expires =
DateTime.Now.AddDays(1);
lblPrevLogin.BackColor = System.Drawing.Color.Green;
}
protected void
btnYellow_Click(object sender,
EventArgs e)
{
Response.Cookies["color"].Value =
"Yellow";
Response.Cookies["color"].Expires =
DateTime.Now.AddDays(1);
lblPrevLogin.BackColor = System.Drawing.Color.Yellow;
}
