Let's do a social engineering experiment. You see, ReSharper has been ignoring pageParserFilter code in asp.net (the thing asp.net MVC and OpenRasta use to enable you to use the C# syntax in your Inherits attribute in asp.net pages) for what feels like forever.
Before the 5.x release, it was still working fine (call it a feature by accident), recognizing the type and enabling full intellisense. Behavior has changed, first by marking everything as an error (in 5.0), and now by compeltley ignoring the base type (5.1). The only reason MVC works is because they special-cased that codebasae, but not OpenRasta's one.
Let's all help JetBrains do the right thing and ask them to re-enable OpenRasta support through a hotfix of their current versions, by voting on this issue: http://youtrack.jetbrains.net/issue/RSRP-92986
In the meantime, you should be able to get by by specifying the old ResourceView`1 syntax in your Inherit clause, or just do like me and don't switch to version 5 just yet.