Register-SPWorkflowService Unable to load one or more of the requested types

I uninstalled SharePoint 2013 preview, azure workflow manager beta on my test machine and reinstalled SharePoint 2013 RTM and windows workflow manager 1.0. However, i got "Unable to load one or more of the requested types" when i run Register-SPWorkflowService PowerShell cmdlet. With fuslogvw, i found out that SharePoint 2013 preview has installed two assemblies C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Microsoft.SharePoint.WorkflowServices.Activities and

C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Microsoft.SharePoint.WorkflowServices.Activities.Design

in the GAC, but SharePoint 2013 RTM don't have these two assembly in the GAC. So, the these two assemblies were left in the GAC after preview version uninstallation and RTM version installation. And these preview version tried to load assembly installed by azure workflow manager beta, which does not exist anymore.

Just delete the two folders

C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Microsoft.SharePoint.WorkflowServices.Activities.Design

And rerun Register-SPworkflowService succeeded.

Register-SPWorkflowService -SPSite "http://win-ftn3aq
s7e1p/sites/dev" -WorkflowHostUri "http://win-ftn3aqs7e1p:12291" -AllowOAuthHttp

Register-SPWorkflowService : Unable to load one or more of the requested types.
 Retrieve the LoaderExceptions property for more information.
At line:1 char:1
+ Register-SPWorkflowService -SPSite "http://win-ftn3aqs7e1p/sites/dev" -Workfl
owH ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~
    + CategoryInfo          : InvalidData: (Microsoft.Share...WorkflowService:
   RegisterSPWorkflowService) [Register-SPWorkflowService], ReflectionTypeLoa
  dException
    + FullyQualifiedErrorId : Microsoft.SharePoint.WorkflowServices.PowerShell
   .RegisterSPWorkflowService