ASP.NET Core & System.Net.Http.Formatting

[smarts]

Is System.Net.Http.Formatting coming to ASP.NET Core? Specifically, ObjectContent, ObjectContent<T>, and the ReadAsAsync<T>() extension methods for HttpClient? I started looking into porting it but the change from MediaTypeFormatter to IInputFormatter and IOutputFormatter - and more generally, the divergence of ASP.NET MVC's and HttpClient's HTTP models - makes things difficult for someone new to ASP.NET Core.
A couple of issues:

• The new formatters' dependence on the entire HttpContext (e.g., see InputFormatterContext) instead of just the type to be deserialized and HttpContent
• No default collection of formatters w/o using dependency injection (to get them from MvcOptions)

[dougbu]

@smarts the System.Net.Http.Formatting.dll assembly and its Microsoft.AspNet.WebApi.Client package are the focus of aspnet/AspNetWebStack#4. We'll ship a new version which explicitly supports .NET Standard 1.1 (and higher).

For now, import the existing package as we do in the Microsoft.AspNetCore.Mvc.WebApiCompatShim project:

{
  "dependencies": {
    "Microsoft.AspNet.WebApi.Client": "5.2.2",
    "NETStandard.Library": "1.6.1-*"
  },
  "frameworks": {
    "netstandard1.6": {
      "imports": [
        "portable-net451+win8"
      ],
      "dependencies": {
        "System.Runtime.Serialization.Xml": "4.3.0-*",
        "System.Xml.XmlSerializer": "4.3.0-*"
      }
    }
  }
}

[smarts]

I get a 404 when I use that issue link, but I'll take your word for it =)

[dougbu]

Right, it's a private repo and I shouldn't have linked to it (yet). We are however working on exactly this issue.

[smarts]

@dougbu do I need all of the JSON you presented? I assumed I just needed the "Microsoft.AspNet.WebApi.Client": "5.2.2" part under "dependencies", but I'm getting an error about that package not supporting the netcoreapp1.0 framework (which my app is targeting).

[dougbu]

Yes, for now the "imports" bit as well as the additional dependencies are required.

[shawnmclean]

So what is the alternative for System.Net.Http.Formatting?

Whats the dotnetcore version of:

return new ObjectContent<T>(body, formatter, mediaType);
// or
return httpResponseMessage.Content.ReadAsAsync<T>(formatters);

[smarts]

currently there isn't one @shawnmclean. you can use the suggestion above to use the old nuget packages in a .net core project. if you want i can provide a snippet that matches the csproj style instead of project.json. alternatively you can wait until the next version of that nuget package is released, which will support .net core.

[shawnmclean]

@smarts yes please, the csproj style is much appreciated. Thanks!

[smarts]

in your csproj…

<PropertyGroup>
    <PackageTargetFallback>$(PackageTargetFallback);dnxcore50;portable-net451+win8</PackageTargetFallback>
</PropertyGroup>
<ItemGroup>
    <PackageReference Include="microsoft.aspnet.webapi.client" Version="5.2.3" />
    <PackageReference Include="system.runtime.serialization.xml" Version="4.3.0" />
    <PackageReference Include="system.xml.xmlserializer" Version="4.3.*" />
</ItemGroup>

[junkomatic]

So how about that .NET Core update for microsoft.aspnet.webapi.client? Still on the way?

[atykhyy]

Here's my approximation to the old ReadAsAsync<T> method targeting netcoreapp2.0. The parts are there, they just need to be put together.

public static T ReadAsAsync<T> (this HttpContext httpContext)
{
    var options  = services.GetRequiredService<IOptions<MvcOptions>> ().Value ;
    var readers  = services.GetRequiredService<IHttpRequestStreamReaderFactory> () ;
    var metadata = services.GetRequiredService<IModelMetadataProvider>          () ;

    var input = new InputFormatterContext (httpContext, String.Empty,
        new ModelStateDictionary (0), metadata.GetMetadataForType (typeof (T)),
        readers.CreateReader) ;

    foreach (var formatter in options.InputFormatters)
        if (formatter.CanRead (input))
        {
            var result = await formatter.ReadAsync (input).ConfigureAwait (false) ;
            if (result.IsModelSet)
                return (T) result.Model ;
        }

    throw new UnsupportedMediaTypeException (...) ;
}

[smarts]

Great effort @atykhyy ! The problem [for me] is that the code above is tied to the ASP.NET Core MVC abstraction(s), not HttpClient and its abstractions.

[atykhyy]

Yes, these are for server-side use. There is a netstandard2.0-compatible version of Microsoft.AspNet.WebApi.Client coming up for the client side. I'm using 5.2.4-alpha1 from the nightly server until the release.

[smarts]

I'm aware of the upcoming package. This issue pre-dates the tracking issue for the upcoming package and is referenced there. Unfortunately, this isn't a case for which a pre-release package is desirable. Thanks for the suggestion though @atykhyy =)

[mguinness]

@junkomatic Looks like support for .NET Core 2.0 has just been added to Microsoft.AspNet.WebApi.Client.