Hosting ASP.NET Core in IIS without Kestrel - iis

Question

Our hosting department is not willing to allow ASP.NET core hosting with Kestrel running or even installing the ASP.NET Core Server Hosting Bundle (AspNetCoreModule).
Is there any alternative to allow ASP.NET core in this situation?
Environment: Windows Server 2012 R2 with latest IIS and .NET 4.6.2.
It is a shared hosting environment and the application(s) must be running in IIS.

Answer 1

You can actually run ASP.NET Core in IIS within the worker process (thus not using the ASP.NET Core Module) by using OWIN.
This is possible due to the fact that ASP.NET Core can be hosted on an OWIN server and IIS can be made an OWIN Server.
Have a look at the following OWIN middleware which shows how to run ASP.NET Core on IIS. For a more complete example, see this gist: https://gist.github.com/oliverhanappi/3720641004576c90407eb3803490d1ce.
public class AspNetCoreOwinMiddleware<TAspNetCoreStartup> : OwinMiddleware, IServer
where TAspNetCoreStartup : class
{
private readonly IWebHost _webHost;
private Func<IOwinContext, Task> _appFunc;
IFeatureCollection IServer.Features { get; } = new FeatureCollection();
public AspNetCoreOwinMiddleware(OwinMiddleware next, IAppBuilder app)
: base(next)
{
var appProperties = new AppProperties(app.Properties);
if (appProperties.OnAppDisposing != default(CancellationToken))
appProperties.OnAppDisposing.Register(Dispose);
_webHost = new WebHostBuilder()
.ConfigureServices(s => s.AddSingleton<IServer>(this))
.UseStartup<TAspNetCoreStartup>()
.Build();
_webHost.Start();
}
void IServer.Start<TContext>(IHttpApplication<TContext> application)
{
_appFunc = async owinContext =>
{
var features = new FeatureCollection(new OwinFeatureCollection(owinContext.Environment));
var context = application.CreateContext(features);
try
{
await application.ProcessRequestAsync(context);
application.DisposeContext(context, null);
}
catch (Exception ex)
{
application.DisposeContext(context, ex);
throw;
}
};
}
public override Task Invoke(IOwinContext context)
{
if (_appFunc == null)
throw new InvalidOperationException("ASP.NET Core Web Host not started.");
return _appFunc(context);
}
public void Dispose()
{
_webHost.Dispose();
}
}

Answer 2

Yes, you could use WebListener web server instead of Kestrel. WebListener only works on the Windows platform but since that is where you are running, it's an option for you.
WebListener however does not rely on IIS as a reverse proxy, in fact WebListener can't be used with IIS or IIS Express since it's not compatible with ASP.NET Core Module. But it does give you a non Kestrel option for hosting ASP.NET Core on windows.
You can learn more about it here: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/servers/weblistener
Prior to ASP.Net Core 2.2
If you must host in IIS and you don't want to use Kestrel and you are running on windows, then there are no options. On Windows, you either host with WebListener without IIS or you host with Kestrel using IIS as a reverse proxy. Those are your only two options currently on Windows.
Update: ASP.Net Core 2.2 or later Starting in ASP.Net Core 2.2 there is now support for running ASP.Net Core In Process in IIS. Under such a configuration Kestrel is not used. To learn more see In Process Hosting Model on the Microsoft Docs site or this blog post https://weblog.west-wind.com/posts/2019/Mar/16/ASPNET-Core-Hosting-on-IIS-with-ASPNET-Core-22