ASP.NET in a Nutshell

State Management

In a typical web page, it is very common for data entry forms to retain their values after the form has been posted and the same page is returned to the client (that is, to retain the values from a posted form in the postback). To implement this feature in classic ASP, you need to determine whether or not the page is requested by a client for the first time. You also need to write code that will display the submitted value in the controls. In contrast, ASP.NET performs state management automatically in postbacks.

ASP.NET uses a simple hidden HTML form field to retain the values automatically during postbacks. There are no ActiveX controls or applets or client-side scripts used to maintain state. Thus, you need not write code to retain values explicitly.

Warning

ASP.NET maintains only the state of server controls -- i.e., the controls declared with the runat="server" attribute/value pair. State management can be enabled or disabled for individual controls or an entire page by setting the MaintainState property to True (its default value) or False.

Now let’s revisit the concept of ViewState, which was introduced earlier in this chapter. ViewState is a collection of information about the properties of an ASP.NET page and its controls (maintained in a hidden form field named _VIEWSTATE .) It exists solely to store the properties of controls that are not transmitted between client and server during postbacks. As the name itself implies, ViewState preserves the state ...