var sreg = response.GetExtension(); return null into mvc-3 application

my webconfig code is:
<?xml version="1.0"?> <!-- For more information on how to configure your ASP.NET application, please visit http://go.microsoft.com/fwlink/?LinkId=152368 --> <configuration> <configSections> <section name="dotNetOpenAuth" type="DotNetOpenAuth.Configuration.DotNetOpenAuthSection" requirePermission="false" allowLocation="true"/> <sectionGroup name="system.serviceModel"> <section name="domainServices" type="System.ServiceModel.DomainServices.Hosting.DomainServicesSection, System.ServiceModel.DomainServices.Hosting, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" allowDefinition="MachineToApplication" requirePermission="false" /> </sectionGroup> </configSections> <dotNetOpenAuth> <openid> <relyingParty> <behaviors> <!-- The following OPTIONAL behavior a ...