Allows server controls to automatically register a hidden field on the form. The field will be sent to the System.Web.UI.Page object when the System.Web.UI.HtmlControls.HtmlForm server control is rendered.
The Page.RegisterHiddenField(string, string) method has been deprecated. Use the ClientScriptManager.RegisterHiddenField(string, string) method in the System.Web.UI.ClientScriptManager class.