Search Service

I have SharePoint 2013 and when I do a search in my site, I get search can not be completed because no search service is available.  I do have the search service started and search service application.  When I click on search service application in central admin, I get An error occurred during the
compilation of the requested file, or one of its dependencies. The name
'IsSearchApplicationExtended' does not exist in the current context

Any way to fix this issue.