Combining EF6 with ASP.NET 5

2 minute read

For some upcoming work my team is doing, we wanted to use Entity Framework as our base DAL (with a micro-mapper like Dapper overlaid on top) and ASP.NET 5 as our web stack. However, Entity Framework 7 (in development alongside ASP.NET) won’t be ready for prime-time according to this blog post by Rowan Miller of the EF team. In particular, lazy loading and inheritance mapping are going to be missing. We were able to make Entity Framework 6 and the associated tools work with some clever use of new features in ASP.NET.

My first attempt was to naively add the package reference to the project.json file, which did not work. I later learned from @davidfowl that the Powershell scripts aren’t run for packages in ASP.NET 5 projects because they’re not cross-platform. Since we wanted to use the code-first approach, this was not viable.

My next attempt was to run the Powershell scripts manually (they were unpacked into the package cache directory) and get them loaded into the right context so that we could use them inside Visual Studio. This didn’t work, as the scripts needed variables from Visual Studio that I couldn’t reproduce.

The next attempt was to create a new “classic” class library project and add EF6 to that. The Powershell tools work from here, but we have one small problem: we can’t reference this project from the ASP.NET 5 project—it doesn’t get resolved as a reference. The final solution combined this with a clever hack enabled by the project.json file’s flexibility:

  1. Use the classic class library we just created.
  2. Add the EF6 reference and any other necessary references to the ASP.NET 5 Class Library project. Keep this reference list in sync.
  3. Adjust the project.json file’s code section for the ASP.NET 5 class library to transclude the EF6 project’s code files: "code": [ "**/*.cs", "../EF6Project/**/*.cs" ].
  4. Reference this project from the web app project.
  5. Profit!

What’s happening here is that we’re using the project.json file’s flexibility to transclude the source files from the “wrapper” project for EF6 into the ASP.NET 5 class library, and keeping the references in sync means the compiler works just fine all the way up the chain.

This lets us use EF6’s features that aren’t yet in EF7, and use the EF6 tools at the same time. Unfortunately, it doesn’t do anything for us to make it easier to port to EF7 down the road, as they’re not likely to be source-compatible, but that’s a bridge to cross later on.

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