State Management in ASP.NET
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, 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 let’s dive into it.
Mainly there are two different ways to manage web page’s state
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 client’s computer.
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 information from cookies.
//to create a cookie variable
//to access a cookie variable
2) 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 fieldHidden1.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 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 informationViewState.Add(“shape”,”circle”);//to retrieve informationstring shapes=ViewState[“shape”];
Note: Unlike Hidden Field, the values in ViewState are invisible when ‘view source’, they are compressed and encoded.
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.
1. http://www.csharphelp.com/archives/archive207.html – Eric Zheng