Download
Download source code for Chat Application Using Application State Object
In this article, I will explain small
chatting example by using Application Object, I will also discuss the various events
in Global.asax file.
Application State:
Application
State is one of the Server Side
State management
Mechanism which stores application memory on the server rather than persisting
data in the client side memory.If we declare any application variable in a
single project, it will be accessible along the website. It will optimize the
performance of the website rather than storing the data in database. Application variables save the memory by
creating instance to HttpApplicationState class. We can use that variable in all pages throughout the
project. Memory of
Application Variable expires until we close the Web Project from the web server.
e.g.
//Defining App Variables –In Global.asax file
DataSet ds=new DataSet ();
Application [“KeyVal”] =ds;
//Using App Variables
DataSet ds= (DataSet) (Application [“KeyVal”]);
Gridview1.DataSource=ds.Tables [0];
Gridview1.DataBound ();
Global Application Class [Global.asax]
Application state only achieved
by adding Global.asax file into our project, it not mandatory to define
Global.asax file web project, if you have not added Global.asax file, ASP.NET
Runtime detects that there was no Application Statemangement in the current
project.
Events in Global.asax File
Some of the Events in
Global.asax file are depicted as follows; this is not a complete list of
events.
Application_Start: This
event fires executes when the application starts running
Application_End: This
event ocurs on application shutdown
Application_Error: This
event ocurs when unhandled error occurs
Session_Start: This
event ocurs when new session is started.
Session_End: This
event occurs when session ends
Hands on Chat Application:
This is very small application,
just like kids play so
there is no need to prolong my explanation on this case study by explaining
each and every control and all.
Step-1:
Design web form as follows by
using three textboxes and one image button. The size of the window was managed
by using java script window.open () method. I created two pages one is
Defalut.aspx and another one is chat.aspx. On form load event of Default.aspx,
I opened chat.aspx as a popup window.
Defalut.aspx (Source Code)
<script language="JavaScript" type
="text/javascript">
function popup()
{
var newWin
= window.open("Chat.aspx", 'method_desc', 'width=250,height=500,left=350,top=120')
}
</script>
<body onload="popup(); return
false;">
</body
>
Chat.aspx (Page Design)
Step-2
Add Global.asax file in you web
application and manage add the code as follows
<script runat="server">
void
Application_Start(object sender, EventArgs e)
{
// Code that
runs on application startup
Application.Lock();
Application["msg"]
= "";
Application.UnLock();
}
void
Application_End(object sender, EventArgs e)
{
//Code that runs on application shutdown
}
void
Application_Error(object sender, EventArgs e)
{
// Code that
runs when an unhandled error occurs
}
void
Session_Start(object sender, EventArgs e)
{
// Code that
runs when a new session is started
}
void
Session_End(object sender, EventArgs e)
{
// Code that
runs when a session ends.
// Note: The
Session_End event is raised only when the sessionstate mode
// is set to
InProc in the Web.config file. If session mode is set to StateServer
// or
SQLServer, the event is not raised.
}
</script>
Step: 3
protected void Page_Load(object
sender, EventArgs e)
{
//Assigning
Application Object to string Varaiable by Parsing
string
msg = (string)Application["msg"];
txtchat.Text = msg;
}
protected void ImageButton1_Click(object
sender, ImageClickEventArgs e)
{
string
nickname = txtnickname.Text;
string
chatmessage = txtmessage.Text;
string mymessage
= nickname +"::" + chatmessage;
//Appending
the User Entered Data To Application["msg"] object
Application["msg"]
= Application["msg"] + mymessage + Environment.NewLine;
//Finally
Dispaling on the Chat Content
txtchat.Text = Application["msg"].ToString();
txtmessage.Text = "";
}
Step-4
Run the application in Browser
and deploy it on your local IIS or access the URI in two browser and Check it
will maintain the State each use session and finally my content was as follows
Here I completed only global chat without taking any session expiration
and all. This is not a Full round trip for Private chat even; this is just for
understanding the Application
State of a web
application.
Conclusion
I hope this article will
give brief idea on how to use Application
Server State
by Using Application Object. Application state variable expires after Stopping Web
Server. So in order to maintain the State Permanently we will go for Customized
Caching to persist the state of the Server.
If you like this article, subscribe to our 
RSS Feed. You can also subscribe via email to our Interview Questions, Codes and Forums section.