Expose WebHostBuilderContext in UseKestrel #1334

Author: Tratcher

samples/SampleApp/Startup.cs

@@ -43,22 +43,15 @@ public static Task Main(string[] args)
                 Console.WriteLine("Unobserved exception: {0}", e.Exception);
             };
 
-            var configuration = new ConfigurationBuilder()
-                .AddEnvironmentVariables()
-                .Build();
-
-            if (!ushort.TryParse(configuration["BASE_PORT"], NumberStyles.None, CultureInfo.InvariantCulture, out var basePort))
-            {
-                basePort = 5000;
-            }
-
             var hostBuilder = new WebHostBuilder()
                 .ConfigureLogging((_, factory) =>
                 {
                     factory.AddConsole();
                 })
-                .UseKestrel(options =>
+                .UseKestrel((context, options) =>
                 {
+                    var basePort = context.Configuration.GetValue<int?>("BASE_PORT") ?? 5000;
+
                     // Run callbacks on the transport thread
                     options.ApplicationSchedulingMode = SchedulingMode.Inline;
 

src/Kestrel/WebHostBuilderKestrelExtensions.cs

@@ -57,5 +57,31 @@ public static IWebHostBuilder UseKestrel(this IWebHostBuilder hostBuilder, Actio
                 services.Configure(options);
             });
         }
+
+        /// <summary>
+        /// Specify Kestrel as the server to be used by the web host.
+        /// </summary>
+        /// <param name="hostBuilder">
+        /// The Microsoft.AspNetCore.Hosting.IWebHostBuilder to configure.
+        /// </param>
+        /// <param name="configureOptions">A callback to configure Kestrel options.</param>
+        /// <returns>
+        /// The Microsoft.AspNetCore.Hosting.IWebHostBuilder.
+        /// </returns>
+        public static IWebHostBuilder UseKestrel(this IWebHostBuilder hostBuilder, Action<WebHostBuilderContext, KestrelServerOptions> configureOptions)
+        {
+            if (configureOptions == null)
+            {
+                throw new ArgumentNullException(nameof(configureOptions));
+            }
+
+            return hostBuilder.UseKestrel().ConfigureServices((context, services) =>
+            {
+                services.Configure<KestrelServerOptions>(options =>
+                {
+                    configureOptions(context, options);
+                });
+            });
+        }
     }
 }