Use objects such as Application, Session, Cookie, and ViewState

ASP. NET contains many types of objects that store information, such as APPlication, Session, Cookie, ViewState, and Cache. What are their differences? What is the environment for each object application?
   For a clearer understanding, we have summarized the specific environment of each object application, as shown in the following table:

Method	Information size	Save time	Application Scope	Save location
Application	Any size	Entire application life cycle	All users	Server
Session	Small amount, simple data	User Activity time + A delay period (average 20 minutes)	Single User	Server
Cookie	Small amount, simple data	Can be set as needed	Single User	Client
Viewstate	Small amount, simple data	Life cycle of a web page	Single User	Client
Cache	Any size	Can be set as needed	All users	Server
Hide domain	Small amount, simple data	Life cycle of a web page	Single User	Client
Query string	Small amount, simple data	Until the next page Jump request	Single User	Client
Web. Config file	A small amount of data that remains unchanged or rarely changed	Until the configuration file is updated	Single User	Server

 1. Application Object
   Application is used to save the public data information of all users. If the Application object is used, a problem to be considered is that any write operation must be performed on the Application_OnStart event (global. asax. although Application. lock and Applicaiton. the Unlock method is used to avoid synchronization of write operations. However, it serializes the requests to the Application object. When the site traffic is large, it will produce a serious performance bottleneck. therefore, it is best not to use this object to store large data sets. the following is an example of online user statistics to illustrate this problem:
   (Store the total website traffic in the form of files)
   (1) Global. asax class
(2) WebForm1.aspx

Private Void Page_Load (object Sender, System. EventArgs E)
                {
                        This. Label1.Text = "Number of users accessing the site :" + Application ["CurrentGuests"]. ToString ();      
                        This. Label2.Text = "Total number of users who have visited the site :" + Application ["AllGuests"]. ToString ();
                }