Pro ASP.NET 3.5 Server Controls and AJAX Components

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Rob Cameron and Dale Michalk

"Pro ASP.NET 3.5 Server Controls and AJAX Components"

Unlike the URL string and cookie options, size limitations and device
support issues are not pressing concerns, so hidden input variables as part of an HTML form
are a heavily used technique for client-side state management.
For data stored in an HTML form to be available, the use of the HTTP POST mechanism is
required to transmit the state information back to the web server. ASP.NET helps ensure this
through the System.Web.UI.HtmlControls.HtmlInputForm server control. HtmlInputForm is smart
enough to render a method="post" attribute, along with an action attribute that directs the page
back to the original URL. The following tag on a hypothetical web form named first.aspx is
rendered as a server control because of the runat="server" attribute:

92 CHAPTER 3 ?– ASP.NET S TATE MANAGEMENT
The server control representing the form tag emits the following HTML output:

Notice that the tag is tied to the HTTP POST protocol and has an action attribute to submit
the page back to the original URL of the web page. Ensuring that all emitted form variables,
hidden or not, can be read upon form submission is a key requirement. Here??™s the complete
form output for our simple example:
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Rob Cameron and Dale Michalk

"Pro ASP.NET 3.5 Server Controls and AJAX Components"