aspnetcore: Can't load Microsoft.AspNetCore.Hosting 1.1.0.0

In the course of trying to help the EF Core team verify that a bug I’d run across was fixed in v1.1, I updated a functioning solution to both EF Core 1.1 and AspNet Core 1.1.

And I really, really, wish I hadn’t.

First off, my previously-functioning MVC6 site stopped working, complaining about a version mismatch on Microsoft.Logging.Abstractions (I think it involved not being able to find v1.0.0 of that assembly).

So I figured I’d just revert everything back to where it was before I did the test for the EF Core team. That should fix everything, right?

Wrong.

Now I’m getting the following:

System.IO.FileLoadException was unhandled Message: An unhandled exception of type ‘System.IO.FileLoadException’ occurred in Unknown Module. Additional information: Could not load file or assembly ‘Microsoft.AspNetCore.Hosting, Version=1.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60’ or one of its dependencies. The located assembly’s manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Here’s the project.json file for the MVC6 app:

{
  "userSecretsId": "aspnet-ConnellCampaigns-ddb1a50a-eba1-4870-91d4-4d26457f64ce",

  "dependencies": {
    "AutoMapper": "5.1.1",
    "BundlerMinifier.Core": "2.2.296",
    "ConnellData": "1.0.0-*",
    "ConnellDataCore": "1.0.0-*",
    "Microsoft.AspNetCore.Authentication.Cookies": "1.0.0",
    "Microsoft.AspNetCore.Diagnostics": "1.0.0",
    "Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore": "1.0.0",
    "Microsoft.AspNetCore.Identity.EntityFrameworkCore": "1.0.0",
    "Microsoft.AspNetCore.Mvc": "1.0.1",
    "Microsoft.AspNetCore.Razor.Tools": {
      "version": "1.0.0-preview2-final",
      "type": "build"
    },
    "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.1",
    "Microsoft.AspNetCore.StaticFiles": "1.0.0",
    "Microsoft.Azure.WebJobs": "1.1.2",
    "Microsoft.EntityFrameworkCore.SqlServer": "1.0.1",
    "Microsoft.EntityFrameworkCore.SqlServer.Design": "1.0.1",
    "Microsoft.EntityFrameworkCore.Tools": {
      "version": "1.0.0-preview2-final",
      "type": "build"
    },
    "Microsoft.Extensions.Caching.Memory": "1.0.0",
    "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
    "Microsoft.Extensions.Configuration.Json": "1.0.0",
    "Microsoft.Extensions.Configuration.UserSecrets": "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",
    "Microsoft.VisualStudio.Web.BrowserLink.Loader": "14.0.0",
    "Microsoft.VisualStudio.Web.CodeGeneration.Tools": {
      "version": "1.0.0-preview2-final",
      "type": "build"
    },
    "Microsoft.VisualStudio.Web.CodeGenerators.Mvc": {
      "version": "1.0.0-preview2-final",
      "type": "build"
    },
    "Microsoft.WindowsAzure.ConfigurationManager": "3.2.3",
    "Serilog": "2.3.0",
    "Serilog.Extensions.Logging": "1.2.0",
    "Serilog.Sinks.Literate": "2.0.0",
    "Serilog.Sinks.RollingFile": "3.2.0",
    "UploadFramework": "1.0.0-*",
    "WindowsAzure.Storage": "7.2.1"
  },

  "tools": {
    "BundlerMinifier.Core": "2.0.238",
    "Microsoft.AspNetCore.Razor.Tools": "1.0.0-preview2-final",
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.0.0-preview2-final",
    "Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",
    "Microsoft.Extensions.SecretManager.Tools": "1.0.0-preview2-final",
    "Microsoft.VisualStudio.Web.CodeGeneration.Tools": {
      "version": "1.0.0-preview2-final",
      "imports": [
        "portable-net45+win8"
      ]
    }
  },

  "frameworks": {
    "net46": {
      "frameworkAssemblies": {
        "System.IO.Compression": "4.0.0.0"
      },
      "dependencies": {
      }
    }
  },

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

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

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

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

I’d appreciate help in getting me back to my paying work 😃. Also advice on how to diagnose this kind of problem in the future (other than never, ever, ever offering to test things 😃).