ASP.NET 4.0 HiddenFields
HiddenField hidCurrentFooterLinks = (HiddenField)gvTaxonomy.FindControl("hidCurrentFooterLinks");
hidCurrentFooterLinks.Value = txtFooterLinkCurrentYear.Text;
HiddenField hidPreviousFooterLinks = (HiddenField)gvTaxonomy.FindControl("hidPreviousFooterLinks");
hidPreviousFooterLinks.Value = txtFooterLinkPreviousYear.Text;
txtFooterLinkCurrentYear.Text = "";
txtFooterLinkPreviousYear.Text = "";

if ((hidCurrentFooterLinks != null) || (hidPreviousFooterLinks != null)) {  // DO SOMETHING   }