public GenericWebHostBuilder(IHostBuilder builder)
{
_builder = builder;
_config = new ConfigurationBuilder()
.AddEnvironmentVariables(prefix: "ASPNETCORE_")
.Build();
_builder.ConfigureHostConfiguration(config =>
{
config.AddConfiguration(_config);
// We do this super early but still late enough that we can process the configuration
// wired up by calls to UseSetting
ExecuteHostingStartups();
});
// IHostingStartup needs to be executed before any direct methods on the builder
// so register these callbacks first
_builder.ConfigureAppConfiguration((context, configurationBuilder) =>
{
if (_hostingStartupWebHostBuilder != null)
{
var webhostContext = GetWebHostBuilderContext(context);
_hostingStartupWebHostBuilder.ConfigureAppConfiguration(webhostContext, configurationBuilder);
}
});
_builder.ConfigureServices((context, services) =>
{
if (_hostingStartupWebHostBuilder != null)
{
var webhostContext = GetWebHostBuilderContext(context);
_hostingStartupWebHostBuilder.ConfigureServices(webhostContext, services);
}
});
_builder.ConfigureServices((context, services) =>
{
var webhostContext = GetWebHostBuilderContext(context);
var webHostOptions = (WebHostOptions)context.Properties[typeof(WebHostOptions)];
// Add the IHostingEnvironment and IApplicationLifetime from Microsoft.AspNetCore.Hosting
services.AddSingleton(webhostContext.HostingEnvironment);
services.AddSingleton <IApplicationLifetime, GenericWebHostApplicationLifetime>();
services.Configure <GenericWebHostServiceOptions>(options =>
{
// Set the options
options.WebHostOptions = webHostOptions;
// Store and forward any startup errors
options.HostingStartupExceptions = _hostingStartupErrors;
});
services.AddHostedService <GenericWebHostService>();
// REVIEW: This is bad since we don't own this type. Anybody could add one of these and it would mess things up
// We need to flow this differently
var listener = new DiagnosticListener("Microsoft.AspNetCore");
services.TryAddSingleton <DiagnosticListener>(listener);
services.TryAddSingleton <DiagnosticSource>(listener);
services.TryAddSingleton <IHttpContextFactory, DefaultHttpContextFactory>();
services.TryAddScoped <IMiddlewareFactory, MiddlewareFactory>();
services.TryAddSingleton <IApplicationBuilderFactory, ApplicationBuilderFactory>();
// Support UseStartup(assemblyName)
if (!string.IsNullOrEmpty(webHostOptions.StartupAssembly))
{
try
{
var startupType = StartupLoader.FindStartupType(webHostOptions.StartupAssembly, webhostContext.HostingEnvironment.EnvironmentName);
UseStartup(startupType, context, services);
}
catch (Exception ex) when(webHostOptions.CaptureStartupErrors)
{
var capture = ExceptionDispatchInfo.Capture(ex);
services.Configure <GenericWebHostServiceOptions>(options =>
{
options.ConfigureApplication = app =>
{
// Throw if there was any errors initializing startup
capture.Throw();
};
});
}
}
});
}
private void UseStartup(Type startupType, HostBuilderContext context, IServiceCollection services)
{
var webHostBuilderContext = GetWebHostBuilderContext(context);
var webHostOptions = (WebHostOptions)context.Properties[typeof(WebHostOptions)];
ExceptionDispatchInfo startupError = null;
object instance = null;
ConfigureBuilder configureBuilder = null;
try
{
// We cannot support methods that return IServiceProvider as that is terminal and we need ConfigureServices to compose
if (typeof(IStartup).IsAssignableFrom(startupType))
{
throw new NotSupportedException($"{typeof(IStartup)} isn't supported");
}
instance = ActivatorUtilities.CreateInstance(new HostServiceProvider(webHostBuilderContext), startupType);
context.Properties[_startupKey] = instance;
// Startup.ConfigureServices
var configureServicesBuilder = StartupLoader.FindConfigureServicesDelegate(startupType, context.HostingEnvironment.EnvironmentName);
var configureServices = configureServicesBuilder.Build(instance);
configureServices(services);
// REVIEW: We're doing this in the callback so that we have access to the hosting environment
// Startup.ConfigureContainer
var configureContainerBuilder = StartupLoader.FindConfigureContainerDelegate(startupType, context.HostingEnvironment.EnvironmentName);
if (configureContainerBuilder.MethodInfo != null)
{
var containerType = configureContainerBuilder.GetContainerType();
// Store the builder in the property bag
_builder.Properties[typeof(ConfigureContainerBuilder)] = configureContainerBuilder;
var actionType = typeof(Action <,>).MakeGenericType(typeof(HostBuilderContext), containerType);
// Get the private ConfigureContainer method on this type then close over the container type
var configureCallback = GetType().GetMethod(nameof(ConfigureContainer), BindingFlags.NonPublic | BindingFlags.Instance)
.MakeGenericMethod(containerType)
.CreateDelegate(actionType, this);
// _builder.ConfigureContainer<T>(ConfigureContainer);
typeof(IHostBuilder).GetMethods().First(m => m.Name == nameof(IHostBuilder.ConfigureContainer))
.MakeGenericMethod(containerType)
.Invoke(_builder, new object[] { configureCallback });
}
// Resolve Configure after calling ConfigureServices and ConfigureContainer
configureBuilder = StartupLoader.FindConfigureDelegate(startupType, context.HostingEnvironment.EnvironmentName);
}
catch (Exception ex) when(webHostOptions.CaptureStartupErrors)
{
startupError = ExceptionDispatchInfo.Capture(ex);
}
// Startup.Configure
services.Configure <GenericWebHostServiceOptions>(options =>
{
options.ConfigureApplication = app =>
{
// Throw if there was any errors initializing startup
startupError?.Throw();
// Execute Startup.Configure
if (instance != null && configureBuilder != null)
{
configureBuilder.Build(instance)(app);
}
};
});
}
