Referencing a .NET 4.6 project from ASP.NET 5 causes build error

Question

In my ASP.NET 5 RC1 project (targeting only dnx46) I'm trying to add a reference to a (classic) Class Library project targeting .net 4.6.

I get this error at build time: ...\MSBuild\14.0\bin\Microsoft.Common.CurrentVersion.targets(1819,5): warning MSB3274: The primary reference "...\ClassLibrary1.dll" could not be resolved because it was built against the ".NETFramework,Version=v4.6" framework. This is a higher version than the currently targeted framework ".NETFramework,Version=v4.5.1".

Why is this happening? My ASP.NET 5 project isn't targeting 4.5.1. According to the project.json file it's only targeting dnx46. I can't find any mention of .net 4.5.1 anywhere.

Here's the project.json for my WebApplication project:

{
  "version": "1.0.0-*",
  "compilationOptions": {
    "emitEntryPoint": true
  },

  "dependencies": {
    "Microsoft.AspNet.IISPlatformHandler": "1.0.0-rc1-final",
    "Microsoft.AspNet.Server.Kestrel": "1.0.0-rc1-final"
  },

  "commands": {
    "web": "Microsoft.AspNet.Server.Kestrel"
  },

  "frameworks": {
    "dnx46": {
      "dependencies": {
        "ClassLibrary1": "1.0.0-*"
      }
    },
  },

  "exclude": [
    "wwwroot",
    "node_modules"
  ],
  "publishExclude": [
    "**.user",
    "**.vspscc"
  ]
}

And here's the project.json that the "wrapping" process creates for my ClassLibrary project:

{
  "version": "1.0.0-*",
  "frameworks": {
    "net46": {
      "wrappedProject": "../../ClassLibrary1/ClassLibrary1.csproj",
      "bin": {
        "assembly": "../../ClassLibrary1/obj/{configuration}/ClassLibrary1.dll",
        "pdb": "../../ClassLibrary1/obj/{configuration}/ClassLibrary1.pdb"
      }
    }
  }
}

Sure, I updated the question to include the project.json files. — BowserKingKoopa, Nov 22 '15 at 21:52
I have the same warning, 4 months later.. but it doesn't seem to be wrong otherwise, it works. — rfcdejong, Feb 17 '16 at 11:52

Sergei Zinovyev · Answer 1 · 2016-04-09T15:52:48.583

2

The warning is still there if built using VS 2015 Update 1, but web app works well and can call a method from .net4.6 assembly.

edited Apr 09 '16 at 15:52

answered Dec 15 '15 at 21:59

Sergei Zinovyev

1,238
14
14

score 1 · Answer 2 · answered Nov 23 '15 at 20:42

1

try to upgrade your utilities and Runtime version if you have't upgraded it yet.

dnvm upgrade

then from the shell point to your working\project folder clean the cache and restore the project packages

dnu clear-http-cache
dnu restore

then try build it

dnu build

answered Nov 23 '15 at 20:42

Hasan Assi

11
1

I think it has nothing to do with dnu, it seems is a MSBuild issue, in RC1 I still have the same issue. Anyway I tried your comment and it's still showing the same warning. – rfcdejong Feb 17 '16 at 11:51

score 0 · Answer 3 · edited May 23 '17 at 11:45

It might be that you're experiencing VS 2015. Setting right target framework for ASP.NET 5 web project. The problem was related to IIS targeting 4.5.1 despite the project targeting the 4.6 framework.

Is your problem happening when you build from Visual Studio or when you run IIS?

The following is working for us.

ClassLibraryNet46

This is a classic .NET Framework class library that has .NET 4.6 as its target framework. There is a one class.

BowserKingKoopa.cs

namespace ClassLibraryNet46
{
    public class BowserKingKoopa
    {
        public static string GetMessage()
        {
            return "Hello to BowserKingKoopa from ClassLibraryNet46!";
        }
    }
}

WebApplicationNetCore

This is an ASP.NET Core Web Application that has only a Startup.cs class. We used Visual Studio to add the reference to the Net46 project (right click, add reference...)

Startup.cs

using Microsoft.AspNet.Builder;
using Microsoft.AspNet.Hosting;
using Microsoft.AspNet.Http;

namespace WebApplicationNetCore
{
    public class Startup
    {
        public void Configure(IApplicationBuilder app)
        {
            app.UseIISPlatformHandler();

            app.Run(async (context) =>
            {
                var message = 
                    ClassLibraryNet46.BowserKingKoopa.GetMessage();

                await context.Response.WriteAsync(message);
            });
        }

        public static void Main(string[] args) => 
            WebApplication.Run<Startup>(args);
    }
}

project.json

{
  "version": "1.0.0-*",
  "compilationOptions": {
    "emitEntryPoint": true
  },

  "dependencies": {
    "Microsoft.AspNet.IISPlatformHandler": "1.0.0-rc1-final",
    "Microsoft.AspNet.Server.Kestrel": "1.0.0-rc1-final"
  },

  "commands": {
    "web": "Microsoft.AspNet.Server.Kestrel"
  },

  "frameworks": {
    "dnx46": {
      "dependencies": {
        "ClassLibraryNet46": "1.0.0-*"
      }
    }
  }
}

Referencing a .NET 4.6 project from ASP.NET 5 causes build error

3 Answers3

ClassLibraryNet46

WebApplicationNetCore

Linked