Microsoft.AspNetCore.Hosting.Abstractions, Version=3.0.0.0 assembly is missing

[martore]

Microsoft.AspNetCore.Hosting.Abstractions, Version=3.0.0.0 assembly is missing

I have created new .NET Core 3.0 project, and moved code from .NET Core 2.1 (so far only Startup.cs and Program.cs) to the new project. When started, the following exception is thrown:

System.IO.FileNotFoundException: 'Could not load file or assembly 'Microsoft.AspNetCore.Hosting.Abstractions, Version=3.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60'. The system cannot find the file specified.'

NuGet package Microsoft.AspNetCore.Hosting.Abstractions version 3.0.0.0 is not available in NuGet Package Manager. There is only 2.2.0 version.

Is there something I am doing wrong here or I will have to wait on Microsoft.AspNetCore.Hosting.Abstractions to be updated to version 3.0.0.0?

Packages I have included in my project:
Microsoft.AspNetCore.App 3.0.0-preview
Microsoft.AspNETCore.App 3.0.0-preview

[Eilon]

@martore can you show what your CSPROJ looks like?

[martore]

ConsoleApp.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp3.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.App" Version="3.0.0-preview-18579-0056" />
  </ItemGroup>

</Project>

Program.cs

using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using System.IO;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateWebHostBuilder(args).Build().Run();
        }

        public static IWebHostBuilder CreateWebHostBuilder(string[] args)
        {
            var config = new ConfigurationBuilder()
                .SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("hostsettings.json", optional: true)
                .AddCommandLine(args)
                .Build();

            return WebHost.CreateDefaultBuilder(args)
                .UseConfiguration(config)
                .UseStartup<Startup>();
        }
    }
}

Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

namespace ConsoleApp
{
    public class Startup
    {
        public IConfiguration Configuration { get; }

        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }
        public void ConfigureServices(IServiceCollection services)
        {

        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {

        }
    }
}

These are installed on PC (beside .NET Core 2.2):

• .NET Core 3.0.0 Preview Build 18579-0056 - Windows Server Hosting
• ASP.NET Core 3.0.0 Preview Build 18579-0056 - Shared Framework
• .NET Core SDK 3.0.100

[Eilon]

Adding @natemcmaster who is an expert on this.

Two things I suspect:

1. This line: <PackageReference Include="Microsoft.AspNetCore.App" Version="3.0.0-preview-18579-0056" /> I think shouldn't have the version specified - it's figured out automatically by the SDK based on other things. Or maybe it's not even needed at all anymore (@natemcmaster ?)
2. The project should be using the Web SDK instead of the plain .NET SDK, so the first line should probably be <Project Sdk="Microsoft.NET.Sdk.Web">

[natemcmaster]

Here is the minimal change you need to make to fix this. cref dotnet/aspnetcore#3612 and https://docs.microsoft.com/en-us/aspnet/core/migration/22-to-30

  <ItemGroup>
-   <PackageReference Include="Microsoft.AspNetCore.App" Version="3.0.0-preview-18579-0056" />
+   <FrameworkReference Include="Microsoft.AspNetCore.App" />
  </ItemGroup>

The preview 2 SDK should resolve this error automatically. dotnet/sdk#2738

[martore]

Changes suggested in #2194 (comment) resolved the issue. Thanks.

[granadacoder]

Changes suggested in #2194 (comment) resolved the issue. Thanks.

Thank you for putting a DIRECT breadcrumb to the answer that resolved it. And not a "got it working" with no details.