T4 template PropertyProcessor error

Question

I need to use property processor="PropertyProcessor" directive for T4 templates using Visual Studio 2010, so I installed GAX 2010 form the IDE's Extension Manager. Although I installed it, the error

**Error 2   A processor named 'PropertyProcessor' could not be found for the directive named 'property'. The transformation will not be run.  The following Exception was thrown:
System.IO.FileNotFoundException: Failed to resolve type for directive processor PropertyProcessor.
   at Microsoft.VisualStudio.TextTemplating.VSHost.TextTemplatingService.ResolveDirectiveProcessor(String processorName)
   at Microsoft.VisualStudio.TextTemplating.Engine.ProcessCustomDirectives(ITextTemplatingEngineHost host, TemplateProcessingSession session, List`1 directivesToBeProcessed)**
still pops up.

What am I doing wrong?