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Session 9
Application, Server
and Session Objects
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Review
To make HTML elements programmatically accessible, it is necessary to
indicate that an HTML element be parsed and treated as a server
control. This can be done by adding a runat="server" attribute to the
HTML element.
The process of checking whether the user has filled up a form in the
right format, and has not left any fields blank, is called validation.
The validation controls available are as follows:
RequiredFieldValidator: Helps in ensuring that a value is entered for a field
CompareValidator: Checks if the value of a control is similar to the value of
another control
RangeValidator: Checks if the value entered in a control is in the specified
range of values
RegularExpressionValidator: Checks if the value entered fits the regular
expression that is specified
CustomValidator: The value entered is checked by a client-side or server-
side function written by the programmer
ValidationSummary: A list of all the validation errors occurring in all the
controls is created, and can be displayed on the page.
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Review Contd…
The Page object has a property called IsValid, that returns true if all the
validation tests are successful, and vice-versa.
To disable client-side validation, the ClientTarget property can be set to
downlevel.
Code Behind is a feature that enables the developer to write the code to
provide the required functionality in a separate file than that of the code
to create the graphics for the web page
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Objectives
Discuss the Global.asax file
Explain the events in the Global.asax file
Use the Application Object
Use the Server Object
Use the Session Object
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Global.asax File
Stored in Root Directory of application
Defines boundary of application
Initialises application or session level variables
Connects to databases
Sends cookies
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Events in Global.asax
Events Description
Application_Start Fired when the first ASP.NET page in the
current application directory (or its sub-
directories) is called.
Application_End
Fired when the last session of the application
ends. Also fired when the web application is
stopped, using the Internet Services Manger
snap-in.
Application_Begin
Request
Fired every time a page request begins (ideally
when a page is loaded or refreshed).
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Events in Global.asax Contd…
Events Description
Application_EndRe
quest
Fired every time a page request ends (that is
every time the page executes on the browser)
Session_Start Fired every time a new session begins.
Session_End Fired when the session ends. For the various
ways in which a session can end, refer to the
session on the Session object.
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Global.asax Example
Global.asax
<script language="C#" runat="server">
protected void Application_Start(Object sender,
EventArgs e)
{
}
protected void Session_Start(Object sender,
EventArgs e)
{
Response.Write( "Session Started <br>");
}
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Global.asax Example
protected void Application_BeginRequest(Object
sender, EventArgs e)
{
Response.Write("<h1>Application
Begins</h1>");
Response.Write ("Application request begins
<br>");
}
protected void Application_EndRequest(Object
sender, EventArgs e)
{
Response.Write ("Application request ends
<br>");
}
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Global.asax Example
protected void Session_End(Object sender, EventArgs
e)
{
Response.Write("Session ended");
}
protected void Application_End (Object sender,
EventArgs e)
{
}
</script>
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Test Global.asax
<html>
<title>Testing Global</title>
<script language="C#" runat="server">
void Page_Load(Object sender, EventArgs e)
{
Response.Write ("Page Load event <br>");
}
</script>
</html>
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Test Global.asax Output
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Application Object
Represents an instance of an ASP.NET application.
Object[varName]
Application ["greeting"] = "Welcome to our sites";
Application Level
Session Level
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Application Object Example 1
void Application_Start(Object sender, EventArgs E)
{
Application ["sessioncount"] = 0;
}
<HTML>
<script Language ="C#" runat ="server" Debug = "true">
void Page_Load(Object Src, EventArgs E)
{
Response.Write (“Your visitor number is “ +
Application ["sessioncount"]);
}
</script>
<form runat= "server" >
</form>
</HTML>
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Application Example Output
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<html>
<script Language ="C#" runat ="server" Debug = "true">
void Page_Load(Object Src, EventArgs E)
{
Response.Write ("Your visitor number is :" + Application
["sessioncount"]);
}
</script>
<form runat= "server" > </form>
</html>
Application Object Example 2
void Session_Start(Object sender, EventArgs e)
{
Application["sessioncount"]=(Int32)Application["sessionco
unt"] + 1;
}
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Application Object Output
Output after reopening
the browser
Output after
refreshing
Output Initially
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Controlling Access
Application variables can be accessed and updated
by all the pages of an ASP.NET application
Since the variable retains the currently assigned
value, if a user changes the value of a variable, the
value is changed for all the users of the application
To ensure that application-level variables are not
updated by more than one user simultaneously, the
Application object makes use of the Lock() and
UnLock() methods.
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Controlling Access Contd…
Application.Lock();
//…code to change the value of the application
variables
……………
…………
Application.UnLock();
The Lock method locks all the variables in a script.
Ensures that only the current user has control
over the page.
When UnLock method is invoked, the current user
loses control of the application
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Arrays
String [] job = new String [4];
job[0]= "Faculty";
job[1]= "Programmer";
job[2]= "Salesman";
job[3]= "Manager";
Application ["j"] = job;
Application-level arrays can be used to share common groups of
information across the entire application.
Typically, application-level arrays are used for information that is
static
While using arrays in the Application object, the elements stored in
the array should not be altered directly
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Array.aspx
<HTML>
<script Language ="C#" runat ="server" >
void Page_Load(Object Src, EventArgs E)
{ int i = 0; String[] k;
k = (String[])Application["j"];
for (i = 0; i<k.Length;i++)
{
Response.Write(k[i] + "<br>");
}
}
</script>
</HTML>
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Server Object
Execute and Transfer
HTMLEncode
URLEncode
MapPath
Property Description
ScriptTimeo
ut
Is used to specify the period for which a script can
run on the server before it is terminated.
MachineName Is used to get the machine name of the server.
Server.property | method
Allows the web server to be controlled, and acts as an
interface to HTTP service
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Execute Method
<%@ Page Debug ="true"%><html>
<script language="C#" runat="server">
void clicked (Object Src, EventArgs E)
{Server.Execute (“Array.aspx");}
</script>
<form runat ="server">
<asp:button id = "btnClick" onclick = "clicked"
Text =" Click me to transfer execution" runat =
"server" />
</form>
</html>
The Execute() method is used to transfer execution from the current
page to another page, and return the execution back to the current
page
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Execute Method Output
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Transfer Method
Server.Transfer (“Array.aspx");
The Transfer() method is used to transfer the execution completely to
the specified page.
Unlike the Execute() method, the control is lost from the calling page
when this method is executed.
Syntax:
