I am getting an error message when using infrastructure namespace in system.data.entity namespace
You need to add a reference to the .NET assembly System.Data.Entity.dll.
You also need a reference to the EntityFramework, or you will get the same error.
I had a similar problem. I made a reference to System.Data.Entity but it was complaining about System.Data.Entity.Infrastructure. The solution was to add the EntityFramework nuget. Once it's installed it actually removes the original System.Data.Entity reference and points to a new DLL that includes System.Data.Entity and System.Data.Entity.Infrastructure.