----------------------------------------------------------- New Message on MumbaiUserGroup
----------------------------------------------------------- From: Swapnil_B1 Message 1 in Discussion Folks, It is something very common and we are using some of the features of ASP.NET like State Management in Web Pages. Since we use these features on day to day basis, it becomes very essential to get clear understanding of it. Let me highlight in detail and the various ways of Managing State in ASP.NET. Web form pages are HTTP-Based, they are stateless, which means they dont know whether the requests are all from the same client, and pages are destroyed and recreated with each round trip to the server, therefore information will be lost, therefore state management is really an issue in developing web applications. We could easily solve these problems in ASP with cookie, query string, application, session and so on. Now in ASP.NET, we still can use these functions, but they are richer and more powerful, so lets dive into it. Mainly there are two different ways to manage web pages state: Client-side and Server-side. 1.Client-side state management : There is no information maintained on the server between round trips. Information will be stored in the page or on the clients computer. A. Cookies. A cookie is a small amount of data stored either in a text file on the client's file system or in-memory in the client browser session. Cookies are mainly used for tracking data settings. Lets take an example: say we want to customize a welcome web page, when the user request the default web page, the application first to detect if the user has logined before, we can retrieve the user informatin from cookies: if (Request.Cookies[username]!=null) lbMessage.text=Dear +Request.Cookies[username].Value+, Welcome shopping here!; else lbMessage.text=Welcome shopping here!; If you want to store clients information, you can use the following code: Response.Cookies[username].Value=username; So next time when the user request the web page, you can easily recongnize the user again. B. Hidden Field A hidden field does not render visibly in the browser, but you can set its properties just as you can with a standard control. When a page is submitted to the server, the content of a hidden field is sent in the HTTP Form collection along with the values of other controls. A hidden field acts as a repository for any page-specific information that you would like to store directly in the page. Hidden field stores a single variable in its value property and must be explicitly added it to the page. ASP.NET provides the HtmlInputHidden control that offers hidden field functionality. protected System.Web.UI.HtmlControls.HtmlInputHidden Hidden1; //to assign a value to Hidden field Hidden1.Value=this is a test; //to retrieve a value string str=Hidden1.Value; Note: Keep in mind, in order to use hidden field, you have to use HTTP-Post method to post web page. Although its name is Hidden, its value is not hidden, you can see its value through view source function. C. View State Each control on a Web Forms page, including the page itself, has a ViewState property, it is a built-in struture for automatic retention of page and control state, which means you dont need to do anything about getting back the data of controls after posting page to the server. Here, which is useful to us is the ViewState property, we can use it to save information between round trips to the server. //to save information ViewState.Add(shape,circle); //to retrieve information string shapes=ViewState[shape]; Note: Unlike Hidden Field, the values in ViewState are invisible when view source, they are compressed and encoded. D. Query Strings Query strings provide a simple but limited way of maintaining some state information.You can easily pass information from one page to another, But most browsers and client devices impose a 255-character limit on the length of the URL. In addition, the query values are exposed to the Internet via the URL so in some cases security may be an issue. A URL with query strings may look like this: http://www.examples.com/list.aspx?categoryid=1&productid=101 When list.aspx is being requested, the category and product information can be obtained by using the following codes: string categoryid, productid; categoryid=Request.Params[categoryid]; productid=Request.Params[productid]; Note: you can only use HTTP-Get method to post the web page, or you will never get the value from query strings. We will see Server Side State management in next article Hope this is useful to you all Swapnil (swaps) http://swapsnet.spaces.live.com/ ----------------------------------------------------------- To stop getting this e-mail, or change how often it arrives, go to your E-mail Settings. http://groups.msn.com/MumbaiUserGroup/_emailsettings.msnw Need help? 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