Application state and Caching in ASP.NET

Question

Hi friends I want to know that what's the application state? What's the difference between application state and caching? Why we used Application state and how?

MuthuMari M · Answer

Hi caching : It is a way to store the frequently used data into the server memory which can be retrieved very quickly. And so provides both scalability and performance . For example if user is required to fetch the same data from database frequently then the resultant data can be stored into the server memory and later retrieved in very less time (better performance). And the same time the application can serve more page request in the same time (scalability). for more info : http://wiki.asp.net/page.aspx/655/caching-in-aspnet/ pls refer this url for application state: http://www.c-sharpcorner.com/uploadfile/annathurai/application-state-in-Asp-Net/ thanks. If this post is useful then mark it as  Accepted Answer

Senthilkumar · Answer

Hi Application state is server side state mechanism. It is used to store the data and it is like global variable. It can be used across the pages and across the users. This has to be used to initialize in the global.asax file. Application[Key] = value; It has the two parts: key and value. The key is used to access the value in the application state. In the Global.asax page void Application_Start(object sender EventArgs e) { // Code that runs on application startup Application[Version] = 1.0; Application[DomainName] = www.google.com; } Inside the .aspx page protected void Page_Load(object sender EventArgs e) { // Code that runs on page load Application[Version] = 1.0; Application[DomainName] = www.google.com; } It's very easy to retrieve application state in the ASP.NET application. I am going to take you to write simple application state program now. string loginID=string.Empty; loginID = Application[LoginID].ToString(); string loginID = string.Empty; loginID = Application.GetKey(0); We can retrieve all application variable on the currently running application's keys by using HttpApplicationState class. HttpApplicationState appState = null; appState = Application.Contents; String[] StateVars = new String[appState.Count]; StateVars = appState.AllKeys; We have three methods to remove application variable from the ASP.NET application. Application.Remove(LoginID); Application.RemoveAt(0); Application.RemoveAll(); Difference: Application and Session State have a very important difference: Application state is a data repository available to all classes in an ASP.NET application. Application state is stored in memory on the server and is faster than storing and retrieving information in a database. Unlike session state which is specific to a single user session application state applies to all users and sessions. Therefore application state is a useful place to store small amounts of often-used data that does not change from one user to another Caching on the other hand allows you to store objects in memory that require extensive server resources to create - it offers powerful features that allow you to customize how items are cached and how long they are cached - you can set extensive properties like priority and expiration. Although they might appear similar they are distinctly separate and have different roles to play in an ASP.NET application in its broadest sense.