Build failing on .net Core app due to missing defi

问题:

I'm trying to build my .NET Core app from the CLI using dotnet build, but every single time I get this error:

'IConfigurationBuilder' does not contain a definition for 'AddEnvironmentVariables' and no extension method 'AddEnvironmentVariables' accepting a first argument of type 'IConfigurationBuilder' could be found (are you missing a using directive or an assembly reference?)

This is my ConfigureServices method in Startup.cs where the problem is happening:

    public void ConfigureServices(IServiceCollection services)
    {
        var builder = new ConfigurationBuilder()
            .AddJsonFile("config.json")
            .AddEnvironmentVariables()
            .Build();

        services.AddEntityFrameworkSqlServer()
             .AddDbContext<MyContext>(options =>
                 options.UseSqlServer(builder["Data:MyContext:ConnectionString"]));

        services.AddIdentity<ApplicationUser, ApplicationRole>()
            .AddEntityFrameworkStores<MyContext>()
            .AddDefaultTokenProviders()
            .AddOpenIddictCore<Application>(config => config.UseEntityFramework());

        services.AddMvc();

        services.AddScoped<OpenIddictManager<ApplicationUser, Application>, CustomOpenIddictManager>();
    }

Looking at this example I see nothing obviously wrong with my Startup.cs.

Update My project.json file:

{
  "compilationOptions": {
    "debugType": "portable",
    "emitEntryPoint": true,
    "preserveCompilationContext": true
  },

  "dependencies": {
    "AspNet.Security.OAuth.Validation": "1.0.0-alpha1-*",
    "Microsoft.AspNetCore.Authentication.Cookies": "1.0.0-rc2-*",
    "Microsoft.AspNetCore.Authentication.JwtBearer": "1.0.0-rc2-*",
    "Microsoft.AspNetCore.Diagnostics": "1.0.0-rc2-*",
    "Microsoft.AspNetCore.Hosting": "1.0.0-rc2-*",
    "Microsoft.AspNetCore.Identity.EntityFrameworkCore": "1.0.0-rc2-*",
    "Microsoft.AspNetCore.IISPlatformHandler": "1.0.0-rc2-*",
    "Microsoft.AspNetCore.Mvc": "1.0.0-rc2-*",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.0-rc2-*",
    "Microsoft.AspNetCore.StaticFiles": "1.0.0-rc2-*",
    "Microsoft.EntityFrameworkCore.SqlServer": "1.0.0-rc2-*",
    "Microsoft.Extensions.Configuration.Json": "1.0.0-rc2-*",
    "Microsoft.Extensions.Logging.Console": "1.0.0-rc2-*",
    "Microsoft.Extensions.Logging.Debug": "1.0.0-rc2-*",
    "OpenIddict.Core": "1.0.0-*",
    "OpenIddict.EF": "1.0.0-*"
  },

  "frameworks": {
    "net451": {
      "frameworkAssemblies": {
        "System.ComponentModel": { "type": "build" }
      }
    },

    "netcoreapp1.0": {
      "dependencies": {
        "Microsoft.NETCore.App": {
          "type": "platform",
          "version": "1.0.0-rc2-*"
        }
      },

      "imports": [
        "dnxcore50",
        "portable-net451+win8"
      ]
    }
  },

  "tools": {
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": {
      "version": "1.0.0-rc2-*",
      "imports": "portable-net45+wp80+win8+wpa81+dnxcore50"
    }
  },

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

  "content": [
    "wwwroot",
    "Views",
    "config.json",
    "web.config"
  ],

  "exclude": [
    "wwwroot",
    "node_modules"
  ],

  "publishExclude": [
    "**.user",
    "**.vspscc"
  ]
}

Oct 2018 Update: This problem does not occur when creating a new .NET Core 2.1 app in the latest build of VS 2017. Everything is now at a long-stable version since I asked this question.

回答1:

You need the Microsoft.Extensions.Configuration namespace in scope to get that extension method. Either fully qualify it, or add this to the top of your file:

using Microsoft.Extensions.Configuration;

You also will need the NuGet reference Microsoft.Extensions.Configuration.EnvironmentVariables.

回答2:

The correct package to add for .AddEnvironmentVariables() is Microsoft.Extensions.Configuration.EnvironmentVariables

回答3:

I tried Microsoft.Extensions.Configuration.EnvironmentVariables but with no luck. I already had Microsoft.Extensions.Configuration from NuGet. I added Microsoft.Extensions.Configuration.UserSecrets and then it worked.