title: DotNetOpenAuth OpenID Provider "Sequence contains more than one element"
body: <p>I'm having trouble implementing my OpenID provider with DNOA 3.4.3. Everything was going absolutely peachy until I needed AX support as well. I set AXFetchAsSregTransform in the web config, as recommended by Andrew at <a href="http://groups.google.com/group/dotnetopenid/browse_thread/thread/5629a24c0a7e8d99" rel="nofollow noreferrer">http://groups.google.com/group/dotnetopenid/browse_thread/thread/5629a24c0a7e8d99</a>. Doing this caused me to get the exception "Sequence Contains More Than One Element" on my decide.aspx page, however, and I haven't been able to get past it.</p>
  
  <p>The following line is throwing the exception:<br>
  <em><strong>Edit:</strong> Strangely enough, this is not the line throwing the error anymore. The SendResponse() is now triggering the exception</em></p>
  
  <p><strike>ClaimsRequest requestedFields = ProviderEndpoint.PendingRequest.GetExtension();</strike></p>
  
  <pre><code>ProviderEndpoint.SendResponse()
  </code></pre>
  
  <p>Any thoughts on why this may be? Any help would be greatly appreciated!</p>
  
  <p>The logs leading up to the error are as follows:</p>
  
  <blockquote><pre>
  2010-04-28 12:38:20,247 (GMT-7) [5] INFO  DotNetOpenAuth.Messaging.Channel - Scanning incoming request for messages: https://myprovider/provider.ashx?openid.ns=http%3A%2F%2Fspecs.openid.net%2Fauth%2F2.0&openid.claimed_id=http%3A%2F%2Fspecs.openid.net%2Fauth%2F2.0%2Fidentifier_select&openid.identity=http%3A%2F%2Fspecs.openid.net%2Fauth%2F2.0%2Fidentifier_select&openid.mode=checkid_setup&openid.ns.ext1=http%3A%2F%2Fopenid.net%2Fsrv%2Fax%2F1.0&openid.ext1.mode=fetch_request&openid.ext1.type.email=http%3A%2F%2Faxschema.org%2Fcontact%2Femail&openid.ext1.type.fullname=http%3A%2F%2Faxschema.org%2FnamePerson&openid.ext1.type.language=http%3A%2F%2Faxschema.org%2Fpref%2Flanguage&openid.ext1.required=email&openid.return_to=http%3A%2F%2Fmyrelyingparty%2Flogin.jsp%3Foidreturn%3D%252Fhome&openid.assoc_handle=%7B634080802953194640%7D%7BHxjFNw==%7D%7B20%7D&openid.realm=http%3A%2F%2Fmyrelyingparty
  2010-04-28 12:38:20,285 (GMT-7) [5] INFO  DotNetOpenAuth.Messaging.Channel - Processing incoming CheckIdRequest (2.0) message:
      openid.claimed_id: http://specs.openid.net/auth/2.0/identifier_select
      openid.identity: http://specs.openid.net/auth/2.0/identifier_select
      openid.assoc_handle: {634080802953194640}{HxjFNw==}{20}
      openid.return_to: http://myrelyingparty/login.jsp?oidreturn=%2Fhome
      openid.realm: http://myrelyingparty/
      openid.mode: checkid_setup
      openid.ns: http://specs.openid.net/auth/2.0
      openid.ns.ext1: http://openid.net/srv/ax/1.0
      openid.ext1.mode: fetch_request
      openid.ext1.type.email: http://axschema.org/contact/email
      openid.ext1.type.fullname: http://axschema.org/namePerson
      openid.ext1.type.language: http://axschema.org/pref/language
      openid.ext1.required: email
  
  2010-04-28 12:38:22,773 (GMT-7) [14] INFO  DotNetOpenAuth.Messaging.Channel - Scanning incoming request for messages: https://myprovider/login.aspx?ReturnUrl=%2fdecide.aspx
  2010-04-28 12:38:36,167 (GMT-7) [5] INFO  DotNetOpenAuth.Messaging.Channel - Scanning incoming request for messages: https://myprovider/login.aspx?ReturnUrl=%2fdecide.aspx
  2010-04-28 12:38:38,147 (GMT-7) [14] ERROR DotNetOpenAuth.Messaging - Protocol error: An HTTP request to the realm URL (http://myrelyingparty/) resulted in a redirect, which is not allowed during relying party discovery.
     at DotNetOpenAuth.Messaging.ErrorUtilities.VerifyProtocol(Boolean condition, String message, Object[] args)
     at DotNetOpenAuth.OpenId.Realm.Discover(IDirectWebRequestHandler requestHandler, Boolean allowRedirects)
     at DotNetOpenAuth.OpenId.Realm.DiscoverReturnToEndpoints(IDirectWebRequestHandler requestHandler, Boolean allowRedirects)
     at DotNetOpenAuth.OpenId.Provider.HostProcessedRequest.IsReturnUrlDiscoverableCore(OpenIdProvider provider)
     at DotNetOpenAuth.OpenId.Provider.HostProcessedRequest.IsReturnUrlDiscoverable(OpenIdProvider provider)
     at OpenIdProviderWebForms.decide.Page_Load(Object src, EventArgs e)
     at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
     at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
     at System.Web.UI.Control.OnLoad(EventArgs e)
     at System.Web.UI.Control.LoadRecursive()
     at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
     at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
     at System.Web.UI.Page.ProcessRequest()
     at System.Web.UI.Page.ProcessRequest(HttpContext context)
     at ASP.decide_aspx.ProcessRequest(HttpContext context)
     at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
     at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
     at System.Web.HttpApplication.PipelineStepManager.ResumeSteps(Exception error)
     at System.Web.HttpApplication.BeginProcessRequestNotification(HttpContext context, AsyncCallback cb)
     at System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context)
     at System.Web.Hosting.PipelineRuntime.ProcessRequestNotificationHelper(IntPtr managedHttpContext, IntPtr nativeRequestContext, IntPtr moduleData, Int32 flags)
     at System.Web.Hosting.PipelineRuntime.ProcessRequestNotification(IntPtr managedHttpContext, IntPtr nativeRequestContext, IntPtr moduleData, Int32 flags)
     at System.Web.Hosting.PipelineRuntime.ProcessRequestNotificationHelper(IntPtr managedHttpContext, IntPtr nativeRequestContext, IntPtr moduleData, Int32 flags)
     at System.Web.Hosting.PipelineRuntime.ProcessRequestNotification(IntPtr managedHttpContext, IntPtr nativeRequestContext, IntPtr moduleData, Int32 flags)
  
  2010-04-28 12:38:38,149 (GMT-7) [14] INFO  DotNetOpenAuth.Yadis - Relying party discovery at URL http://myrelyingparty/ failed.  DotNetOpenAuth.Messaging.ProtocolException: An HTTP request to the realm URL (http://myrelyingparty/) resulted in a redirect, which is not allowed during relying party discovery.
     at DotNetOpenAuth.Messaging.ErrorUtilities.VerifyProtocol(Boolean condition, String message, Object[] args) in c:\TeamCity\buildAgent\work\bf9e2ca68b75a334\src\DotNetOpenAuth\Messaging\ErrorUtilities.cs:line 235
     at DotNetOpenAuth.OpenId.Realm.Discover(IDirectWebRequestHandler requestHandler, Boolean allowRedirects) in c:\TeamCity\buildAgent\work\bf9e2ca68b75a334\src\DotNetOpenAuth\OpenId\Realm.cs:line 446
     at DotNetOpenAuth.OpenId.Realm.DiscoverReturnToEndpoints(IDirectWebRequestHandler requestHandler, Boolean allowRedirects) in c:\TeamCity\buildAgent\work\bf9e2ca68b75a334\src\DotNetOpenAuth\OpenId\Realm.cs:line 424
     at DotNetOpenAuth.OpenId.Provider.HostProcessedRequest.IsReturnUrlDiscoverableCore(OpenIdProvider provider) in c:\TeamCity\buildAgent\work\bf9e2ca68b75a334\src\DotNetOpenAuth\OpenId\Provider\HostProcessedRequest.cs:line 142
  2010-04-28 12:38:42,076 (GMT-7) [8] ERROR OpenIdProviderWebForms.Global - An unhandled exception was raised. Details follow: System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.InvalidOperationException: Sequence contains more than one element
     at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
     at DotNetOpenAuth.OpenId.Provider.Request.GetExtension[T]() in c:\TeamCity\buildAgent\work\bf9e2ca68b75a334\src\DotNetOpenAuth\OpenId\Provider\Request.cs:line 176
     at DotNetOpenAuth.OpenId.Extensions.ExtensionsInteropHelper.ConvertSregToMatchRequest(IHostProcessedRequest request) in c:\TeamCity\buildAgent\work\bf9e2ca68b75a334\src\DotNetOpenAuth\OpenId\Extensions\ExtensionsInteropHelper.cs:line 180
     at DotNetOpenAuth.OpenId.Behaviors.AXFetchAsSregTransform.DotNetOpenAuth.OpenId.Provider.IProviderBehavior.OnOutgoingResponse(IAuthenticationRequest request) in c:\TeamCity\buildAgent\work\bf9e2ca68b75a334\src\DotNetOpenAuth\OpenId\Behaviors\AXFetchAsSregTransform.cs:line 139
     at DotNetOpenAuth.OpenId.Provider.OpenIdProvider.ApplyBehaviorsToResponse(IRequest request) in c:\TeamCity\buildAgent\work\bf9e2ca68b75a334\src\DotNetOpenAuth\OpenId\Provider\OpenIdProvider.cs:line 482
     at DotNetOpenAuth.OpenId.Provider.OpenIdProvider.SendResponse(IRequest request) in c:\TeamCity\buildAgent\work\bf9e2ca68b75a334\src\DotNetOpenAuth\OpenId\Provider\OpenIdProvider.cs:line 325
     at OpenIdProviderWebForms.decide.Yes_Click(Object sender, EventArgs e) in C:\Projects\OpenIdProviderWebForms\decide.aspx.cs:line 130
     at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
     at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
     at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
     at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
     --- End of inner exception stack trace ---
     at System.Web.UI.Page.HandleError(Exception e)
     at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
     at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
     at System.Web.UI.Page.ProcessRequest()
     at System.Web.UI.Page.ProcessRequest(HttpContext context)
     at ASP.decide_aspx.ProcessRequest(HttpContext context) in c:\Windows\Microsoft.NET\Framework64\v2.0.50727\Temporary ASP.NET Files\root\7f580b93\b3e4d917\App_Web_tulh9ymv.1.cs:line 0
     at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
     at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
  </pre>
  </blockquote>