EF6: Document workaround to use EDMX files with EF 6.3 on .NET Core

[divega]

I think we should also consider moving the code sample to this repo (currently it is in my personal GitHub account) and update the aka.ms link.

From the preview 9 blog post:

How to work with EDMX files in .NET Core projects

On the tooling side, we plan to release an updated EF6 designer in an upcoming update of Visual Studio 2019 which will work with projects that target .NET Core (tracked in issue #883). Until this new version of the designer is available, we recommend that you work with your EDMX files inside projects that target .NET Framework. You can then add the EDMX file and the generated classes for the entities and the DbContext as linked files to a .NET Core 3.0 or .NET Standard 2.1 project in the same solution. For example, the project file for the .NET Core project can include the linked files like this:

  <ItemGroup>
    <EntityDeploy Include="..\EdmxDesignHost\Entities.edmx" Link="Model\Entities.edmx" />
    <Compile Include="..\EdmxDesignHost\Entities.Context.cs" Link="Model\Entities.Context.cs" />
    <Compile Include="..\EdmxDesignHost\Thing.cs" Link="Model\Thing.cs" />
    <Compile Include="..\EdmxDesignHost\Person.cs" Link="Model\Person.cs" />
  </ItemGroup>

Note that the EDMX file is linked with the 

EntityDeploy build action. This is a special MSBuild task (now included in the EF 6.3 package) that takes care of adding the EF model into the target assembly as embedded resources (or copying it as files in the output folder, depending on the setting on the Metadata Artifact Processing setting in the EDMX). For more details on how to get this set up, see our EDMX .NET Core sample. You can choose to copy the files instead of linking them, but keep in mind that due to a bug in current builds of Visual Studio, copying the files from the .NET Framework project to the .NET Core project within Solution Explorer may cause hangs, so it is better to copy the files from the command line.

[divega]

cc @bricelam

[Flem100]

Thank you for the sample. It took me a while to figure out that I ofc have to change the namespaces of the generated files when I try to do the process in my own project. Also, if I change anything in the edmx, everything will be regenerated on save and all the namespaces will go back to the EF6 project. Is there a way to change the default namespace for the generated files or is there some kind of workaround I should know about?