Web form pages are HTTP-Based, they are stateless, which means they don’t 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 and state management is a major issue in developing web applications. In this article we review how to handle state manage on the client using ViewState , Cookies, Hidden Fields and QueryStrings.
1. ASP.NET ViewState
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 don’t 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 Fields, the values in ViewState are invisible in the ‘viewsource’ of the page, they are compressed and encoded.
2. ASP.NET 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.
Let’s 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 shoppinghere!”; else lbMessage.text=”Welcome shoppinghere!”;
If you want to storeclient’s information, you can use the following code:
So next time when the user request the web page, you can easily recongnize the user again.
3. ASP.NET Hidden Fields
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 theHTTP 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 tostore directly in the page. Hidden field stores a single variable in itsvalue 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.HtmlInput Hidden Hidden1;
//to assign a value to Hiddenfield Hidden1.Value=”this is a test”;
//to retrieve a value stringstr=Hidden1.Value;
Note: Keep in mind, in orderto 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.
4. ASP.NET QueryStrings
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.Continues…