Structuring an ASP.NET Core project to reference .Net Standard libraries

Question

I am having trouble wrapping my head around framework dependencies of ASP.NET Core Web API and .NET Standard PCLs.

I am creating a new web API (microservice) that will be used as an API gateway, I created a new project in VS2015 (update 3, latest .net core tools) and it compiles and runs fine.

I then added some .NET Standard PCL projects to use to separate out POCOs, Repository layers etc. These all reference each other fine, however when I try to add a reference from my ASP.NET Core Web API I cannot use any of the classes defined in my PCLs.

After some research is seems to be down to the fact that I am targeting different frameworks in the projects, the frameworks section of project.json for the Web API reads:

"frameworks": {
  "netcoreapp1.0": {
    "imports": [
      "dotnet5.6",
      "portable-net45+win8"
    ]
  }
},

And for the PCLs it initially read:

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

It seems clear this is where the incompatibility arises.

To rectify this I attempted to make the .Net core project reference the .Net Standard framework such that it could use the PCLs, however everything I tried failed to allow me to reference the projects.

The only way I have gotten this to work is to do the inverse and make the PCL libraries reference netcoreapp1.0, which feels very wrong.

My full .Net standard project.json now reads:

{
  "version": "1.0.0",

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

  "frameworks": {
    "netstandard1.6": {
      "imports": "dnxcore50"
    },
    "netcoreapp1.0": {
      "imports": [
        "dotnet5.6",
        "portable-net45+win8"
      ]
    }
  }
}

And my full .Net Core Web Api Project reads

{
  "dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.0.1",
      "type": "platform"
    },
    "Microsoft.AspNetCore.Mvc": "1.0.1",
    "Microsoft.AspNetCore.Routing": "1.0.1",
    "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.1",
    "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
    "Microsoft.Extensions.Configuration.FileExtensions": "1.0.0",
    "Microsoft.Extensions.Configuration.Json": "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",
    "Company.Product.Microservices.Gateway.Business": "1.0.0",
    "Company.Product.Microservices.Gateway.DomainObjects": "1.0.0" 
  },

  "tools": {
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.0.0-preview2-final"
  },

  "frameworks": {
    "netcoreapp1.0": {
      "imports": [
        "dotnet5.6",
        "portable-net45+win8"
      ]
    }
  },

  "buildOptions": {
    "emitEntryPoint": true,
    "preserveCompilationContext": true
  },

  "runtimeOptions": {
    "configProperties": {
      "System.GC.Server": true
    }
  },

  "publishOptions": {
    "include": [
      "wwwroot",
      "**/*.cshtml",
      "appsettings.json",
      "web.config"
    ]
  },

  "scripts": {
    "postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
  }
}

As I said earlier, the framework references here seem incorrect. I would assume that a netcoreapp framework based project could reference a .NET Standard project compiled project directly, without the PCL itself having to know anything about netcoreapp, it is a PCL after all.

What is the correct what to structure a project like this, it feels this should be the "default" setup of any ASP.NET Core project however so far it has not been simple to set up and I cannot find any documentation that relates to this surely common scenario. Perhaps that is because my understanding of Core and Standard is incorrect and I'm not doing it right, or perhaps my config is just wrong. Please let me know either way how I should achieve a structure like this correctly.

netcoreapp1.x is only here for applications, not for class libraries. Applications are in general assemblies (dll or exe) with an entry point (static Main method, like console, asp.net core web applications or unit test projects). That being said, your class libraries shouldn't have netcoreapp1.x at all, only your application. netcoreapp1.0 project can reference netstandard1.x — Tseng
– Tseng, Commented Jan 7, 2017 at 18:36
Yeah exactly, this is why I don't like adding it to my PCLs, however I couldn't get the project to compile any other way. If I remove it the compiler says I am missing a reference to my PCLs when I try to build the Web API, despite them being listed in the dependencies json block. — James Ferretti
– James Ferretti, Commented Jan 7, 2017 at 18:39
Playing with this a bit more it seems adding a dependency to .Net Standard 1.6 in the API's project.json allows me to compile without netcoreapi1.x in the PCLs, however I get no intellisense and Visual Studio cannot see the references to my PCLs, despite it compiling (from VS). So while that works it is not an acceptable solution. — James Ferretti
– James Ferretti, Commented Jan 7, 2017 at 18:46
Look at the output window what nuget/package manager outputs while it restores — Tseng
– Tseng, Commented Jan 7, 2017 at 18:57

James Ferretti · Accepted Answer · 2017-01-10 10:42:39Z

3

After some further investigation and help of M.Ob's project.json i figured out that my project was actually building correctly and the issue was coming from ReSharper (10.0.2, I should probably upgrade).

Disabling resharper for this solution has now let my project build and Intellisense work correctly for the solution.

answered Jan 10, 2017 at 10:42

James Ferretti

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2 Comments

M.Ob Over a year ago

Yes, I had issues with ReSharper 10.x.x as well with .NET Core. I finally upgraded to the latest version and had no problems. The latest version integrates nicely with .NET Core.

CodeCaster Over a year ago

Present in ReSharper 2017.1.3 with a netcoreapp2.0 targeting a netstandard2.0 library.

M.Ob · Accepted Answer · 2017-01-09 17:28:19Z

I have a ASP.NET Core app that is broken up into many projects. My web app is the only one that is a netcoreapp1.1. The rest are all netstandard1.6.

Look carefully at my project.json files (specifically the frameworks and dependencies sections) to compare with yours. You'll see the slight differences. My solution builds with no problem and intellisense works as well.

My web app project.json is like this (it is fairly long, but I left everything there in case you needed to see anything else:

{
  "version": "2.0.1.0",

  "dependencies": {
    "DT.Common": "2.*",
    "DT.Configuration": "2.*",
    "DT.Services": "2.*",
    "DT.Web.ViewModels": "2.*",
    "Microsoft.ApplicationInsights.AspNetCore": "1.0.2",
    "Microsoft.AspNetCore.Authentication": "1.1.0",
    "Microsoft.AspNetCore.Authentication.Cookies": "1.1.0",
    "Microsoft.AspNetCore.Authentication.OpenIdConnect": "1.1.0",
    "Microsoft.AspNetCore.Diagnostics": "1.1.0",
    "Microsoft.AspNetCore.Mvc": "1.1.0",
    "Microsoft.AspNetCore.Razor.Tools": {
      "version": "1.1.0-preview4-final",
      "type": "build"
    },
    "Microsoft.AspNetCore.Routing": "1.1.0",
    "Microsoft.AspNetCore.Server.IISIntegration": "1.1.0",
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": {
      "version": "1.1.0-preview4-final",
      "type": "build"
    },
    "Microsoft.AspNetCore.Server.Kestrel": "1.1.0",
    "Microsoft.AspNetCore.Server.Kestrel.Https": "1.1.0",
    "Microsoft.AspNetCore.Session": "1.0.0",
    "Microsoft.AspNetCore.StaticFiles": "1.1.0",
    "Microsoft.Extensions.Caching.SqlServer": "1.0.0",
    "Microsoft.Extensions.Configuration.Abstractions": "1.1.0",
    "Microsoft.Extensions.Configuration.FileExtensions": "1.1.0",
    "Microsoft.Extensions.Configuration.Json": "1.1.0",
    "Microsoft.Extensions.Logging.Console": "1.1.0",
    "Microsoft.Extensions.Logging.Debug": "1.1.0",
    "Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
    "Microsoft.Graph": "1.1.1",
    "Microsoft.IdentityModel.Clients.ActiveDirectory": "3.13.6"
  },

  "tools": {
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.1.0-preview4-final",
    "Microsoft.AspNetCore.Razor.Tools": {
      "version": "1.1.0-preview4-final",
      "imports": "portable-net45+win8+dotnet5.6"
    },
    "Microsoft.Extensions.Caching.SqlConfig.Tools": "1.1.0-preview4-final"
  },

  "frameworks": {
    "netcoreapp1.1": {
      "imports": [
        "dotnet5.6",
        "portable-net45+win8"
      ],
      "dependencies": {
        "Microsoft.NETCore.App": {
          "version": "1.1.0",
          "type": "platform"
        }
      }
    }
  },

  "buildOptions": {
    "emitEntryPoint": true,
    "preserveCompilationContext": true
  },

  "runtimeOptions": {
    "configProperties": {
      "System.GC.Server": true
    }
  },

  "publishOptions": {
    "include": [
      "wwwroot",
      "views/**/*.cshtml",
      "appsettings.json",
      "appsettings.*.json",
      "web.config"
    ]
  },

  "scripts": {
    "prepublish": [ "bower install", "gulp buildprod" ],
    "postpublish": [ "dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%" ]
  }
}

My services layer project.json is like this:

{
  "version": "2.0.1.0",

  "dependencies": {
    "DT.Common": "2.*",
    "DT.Configuration": "2.*",
    "DT.Data": "2.*",
    "DT.Models": "2.*" ,
    "DT.Web.ViewModels": "2.*",
    "Microsoft.ApplicationInsights.AspNetCore": "1.0.2",
    "Microsoft.AspNetCore.Authentication.Cookies": "1.1.0",
    "Microsoft.AspNetCore.Http.Abstractions": "1.1.0",
    "Microsoft.Extensions.Caching.Abstractions": "1.0.0",
    "Microsoft.Extensions.Options": "1.1.0",
    "Microsoft.Graph": "1.1.1",
    "Microsoft.IdentityModel.Clients.ActiveDirectory": "3.13.6"
  },

  "frameworks": {
    "netstandard1.6": {
      "imports": [
        "dotnet5.6",
        "portable-net45+win8"
      ],
      "dependencies": {
        "NETStandard.Library": "1.6.1"
      }
    }
  }
}

My data layer project.json is like this:

{
  "version": "2.0.1.0",

  "dependencies": {
    "DT.Configuration": "2.*",
    "DT.Data.Domain": "2.*",
    "Microsoft.EntityFrameworkCore.SqlServer": "1.0.1",
    "Microsoft.Extensions.Configuration.Abstractions": "1.1.0",
    "Microsoft.Extensions.DependencyInjection.Abstractions": "1.1.0"
  },

  "tools": {
    "Microsoft.EntityFrameworkCore.Tools": "1.1.0-preview4-final"
  },

  "frameworks": {
    "netstandard1.6": {
      "imports": "dotnet5.6",
      "dependencies": {
        "NETStandard.Library": "1.6.1"
      }
    }
  }
}

Thanks for this, it has proved to me my initial feelings that it is unnecessary to reference netcoreapp in the PCL project.json files. It turned out to be ReSharper reporting an error when it didn't need to.

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