asp.net mvc - can't find DisplayModeProvider Class in System.Web.WebPages -

after upgrading mvc3 mvc4 following link upgrading asp.net mvc 3 project asp.net mvc 4 needs changes in config files, working web application when wanted test mobile application , wanted add in global.asax.cs file :

displaymodes.modes.insert(0, new defaultdisplaymode("iphone") {   contextcondition = (context => context.request.useragent.indexof                      ("iphone", stringcomparison.ordinalignorecase) >= 0) }); 

but said cannot find displaymodeprovider class in system.web.webpages ! please

try this

displaymodeprovider.instance.modes.insert(0, new defaultdisplaymode("iphone") {   contextcondition = (context => context.request.useragent.indexof                      ("iphone", stringcomparison.ordinalignorecase) >= 0) });