I am trying the Astoria sample that comes with Dataobjects.net v 4.1.0. When building the Server.Model Project, I get the following error:

Unhandled exception: PostSharp.CodeModel.BindingException: Cannot find the type 'System.Collections.Generic.HashSet`1, System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' in assembly 'System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.
   at PostSharp.CodeModel.AssemblyEnvelope.GetTypeDefinition(String typeName, BindingOptions bindingOptions)
   at PostSharp.CodeModel.TypeRefDeclaration.GetTypeDefinition(BindingOptions bindingOptions)
   at PostSharp.Extensibility.Tasks.IndexGenericInstancesTask.Execute()
   at PostSharp.Extensibility.Project.ExecutePhase(String phase)
   at PostSharp.Extensibility.Project.Execute()
   at PostSharp.Extensibility.PostSharpObject.ExecuteProjects()
   at PostSharp.Extensibility.PostSharpObject.InvokeProjects(ProjectInvocation[] projectInvocations)
   at PostSharp.MSBuild.PostSharpRemoteTask.Execute(PostSharpTaskParameters parameters, TaskLoggingHelper log)  Server.Model

I am using visual studio 2010 RC.

This thread was imported from our support forum. The original discussion may contain more detailed answer. Original topic by muhammadadel.