Referencing .NET 4.6.2 class library from .NET Core app

Question

I'm using VS Update 3 (14.0.25425.01). Here's what I've done:

1. Create ASP.Net Core Web Application (.Net Core)
2. Create Class Library .Net 4.6.2
3. Add net462 to frameworks, netcoreapp1.0, imports in project.json
4. Right click on ASP.Net Core app, click Add Reference, select Projects, select Class Library you created in step 2.

I get no errors on restoring and the reference is added to the ASP.Net Core app. However, I cannot access it. I cannot add a using import declaration or access the objects. I've ran through many things but nothing seems to work and the posts are very versioned fragmented.

Here is the Program.cs in the ASP.Net Core App.

Update I did what Nate suggested. I thought I tried this already..but sure enough I can now access my 4.6.2 libraries. However, I'm now getting compile errors.

Couching

Answer 1

This does work in Visual Studio 2015 Update 3, but your project.json isn't quite right.

Instead of adding net462 to the imports section, it should be in the frameworks section:

"frameworks": {
  "net461": { },
  "netcoreapp1.0": {
    "dependencies": {
      "Microsoft.NETCore.App": {
        "type": "platform",
        "version": "1.0.0"
      }
    }
  }
}

Notice that the Microsoft.NETCore.App dependency also needs to be moved into the netcoreapp1.0 section. That's because this dependency is only required when compiling as a .NET Core application.

The reference to your .NET 4.6.2 library is then simply part of your dependencies section:

"dependencies": {
  (...)
  "Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
  "MyLibrary": {
    "target": "project"
  }
}

By structuring it this way, I was able to reference and use classes in my .NET 4.6.2 library without any problems.

---

For reference, here's the entire working project.json I used:

{
  "dependencies": {
    "Microsoft.AspNetCore.Mvc": "1.0.0",
    "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.0",
    "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
    "Microsoft.Extensions.Configuration.FileExtensions": "1.0.0",
    "Microsoft.Extensions.Configuration.Json": "1.0.0",
    "Microsoft.Extensions.Configuration.CommandLine": "1.0.0",
    "Microsoft.Extensions.Logging": "1.0.0",
    "Microsoft.Extensions.Logging.Console": "1.0.0",
    "Microsoft.Extensions.Logging.Debug": "1.0.0",
    "Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
    "MyLibrary": {
      "target": "project"
    }
  },
  "frameworks": {
    "net461": { },
    "netcoreapp1.0": {
      "dependencies": {
        "Microsoft.NETCore.App": {
          "type": "platform",
          "version": "1.0.0"
        }
      }
    }
  },
  "version": "1.0.0-*"
}

Topeka

Does that actually compile for netcoreapp1.0 or only for net461? – Plourde

@Plourde With both Visual Studio and dotnet build, binaries are produced for both net461 and netcoreapp1.0. – Topeka

How? A netcoreapp1.0 app shouldn't be able to depend on a net461 library, that's just not compatible. – Plourde

@svick...am I doing something wrong here? Do you have a suggestion? – Couching

@NateBarbettini See my Updated question. I know this looks obvious but what impact does this have? The project builds successfully and runs – Couching

Answer 2

@NateBarbettini answer accomplished my original question. But I could not run ASP.Net Core Web Application version 1 with my .Net 4.6.1 project as it was because it could not find a .NetCore.App v1 assembly for my .Net 4.6.1 project. So I added a project.json to my .Net 4.6.1 project with the following project.json.

{
  "version": "1.0.0-*",

  "dependencies": {
  "NETStandard.Library": "1.6.0"
  },

  "frameworks": {
  "netstandard1.6": {
    "imports": "dnxcore50"
   },
  "net461": {}
 }
}

Next, in the ASP.Net Core Web Application modify the project.json by adding a dependency under the .NetCore.App. This way it will pick up both versions, 4.6.1 and .NetCore v1.

...
"frameworks": {
"net461": {
  "dependencies": {
    "ClassLibrary1": {
      "target": "project"
    }
  }
},
"netcoreapp1.0": {
  "imports": [
    "dotnet5.6",
    "portable-net45+win8",
    "net461"
  ],
  "dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.0.0",
      "type": "platform"
    },
    "ClassLibrary1": {
      "target": "project"
    }
  }
}
}

So far so good, I can develop in .Net 4.6.1 and it will work running under .NetCore.App v1. However, I think there will be issues when I have other dependencies in my .Net 4.6.1 projects.

Couching

What other dependencies will cause issues in your .NET 4.6.1 project? – Jodee