ch13 samples

Directory.Packages.props

@@ -18,17 +18,22 @@
     <PackageVersion Include="CommunityToolkit.Aspire.Hosting.Sqlite" Version="13.4.0" />
     <PackageVersion Include="CommunityToolkit.Aspire.Microsoft.EntityFrameworkCore.Sqlite" Version="9.7.2" />
     <PackageVersion Include="FSharp.Core" Version="9.0.300" />
+    <PackageVersion Include="Google.Protobuf" Version="3.36.0" />
+    <PackageVersion Include="Grpc.AspNetCore" Version="2.83.0" />
+    <PackageVersion Include="Grpc.Net.ClientFactory" Version="2.83.0" />
+    <PackageVersion Include="Grpc.Tools" Version="2.83.0" />
     <PackageVersion Include="Microsoft.AspNetCore.Components.WebAssembly" Version="10.0.10" />
     <PackageVersion Include="Microsoft.AspNetCore.Components.WebAssembly.DevServer" Version="10.0.10" />
-    <PackageVersion Include="Microsoft.AspNetCore.Components.WebAssembly.Server" Version="10.0.10" />
-    <PackageVersion Include="Microsoft.AspNetCore.OpenAPI" Version="10.0.10" />
+    <PackageVersion Include="Microsoft.AspNetCore.Components.WebAssembly.Server" Version="10.0.11" />
+    <PackageVersion Include="Microsoft.AspNetCore.OpenAPI" Version="10.0.11" />
+    <PackageVersion Include="Microsoft.AspNetCore.SignalR.Client" Version="10.0.11" />
     <PackageVersion Include="Microsoft.EntityFrameworkCore.Sqlite" Version="10.0.10" />
     <PackageVersion Include="Microsoft.EntityFrameworkCore.Tools" Version="10.0.10" />
-    <PackageVersion Include="Microsoft.Extensions.Hosting" Version="10.0.10" />
+    <PackageVersion Include="Microsoft.Extensions.Hosting" Version="10.0.11" />
     <PackageVersion Include="Microsoft.Extensions.Http" Version="10.0.10" />
-    <PackageVersion Include="Microsoft.Extensions.Http.Resilience" Version="10.8.0" />
-    <PackageVersion Include="Microsoft.Extensions.ServiceDiscovery" Version="10.8.0" />
-    <PackageVersion Include="Microsoft.Extensions.ServiceDiscovery.Yarp" Version="10.8.0" />
+    <PackageVersion Include="Microsoft.Extensions.Http.Resilience" Version="10.9.0" />
+    <PackageVersion Include="Microsoft.Extensions.ServiceDiscovery" Version="10.9.0" />
+    <PackageVersion Include="Microsoft.Extensions.ServiceDiscovery.Yarp" Version="10.9.0" />
     <PackageVersion Include="Microsoft.NET.Runtime.WebAssembly.Wasi.Sdk" Version="10.0.8" />
     <PackageVersion Include="Microsoft.OpenApi" Version="2.3.1" />
     <PackageVersion Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="9.0.0" />
@@ -37,6 +42,7 @@
     <PackageVersion Include="OpenTelemetry" Version="1.17.0" />
     <PackageVersion Include="OpenTelemetry.Api" Version="1.17.0" />
     <PackageVersion Include="OpenTelemetry.Instrumentation.EntityFrameworkCore" Version="1.12.0-beta.2" />
+    <PackageVersion Include="Yarp.ReverseProxy" Version="2.3.0" />
   </ItemGroup>
   <!-- Microsoft common packages -->
   <ItemGroup>
@@ -62,11 +68,11 @@
   </ItemGroup>
   <!-- OpenTelemetry -->
   <ItemGroup>
-    <PackageVersion Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.17.0" />
-    <PackageVersion Include="OpenTelemetry.Extensions.Hosting" Version="1.17.0" />
-    <PackageVersion Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.17.0" />
-    <PackageVersion Include="OpenTelemetry.Instrumentation.Http" Version="1.17.0" />
-    <PackageVersion Include="OpenTelemetry.Instrumentation.Runtime" Version="1.17.0" />
+    <PackageVersion Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.18.0" />
+    <PackageVersion Include="OpenTelemetry.Extensions.Hosting" Version="1.18.0" />
+    <PackageVersion Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.18.0" />
+    <PackageVersion Include="OpenTelemetry.Instrumentation.Http" Version="1.18.0" />
+    <PackageVersion Include="OpenTelemetry.Instrumentation.Runtime" Version="1.18.0" />
     <PackageVersion Include="OpenTelemetry.Instrumentation.GrpcNetClient" Version="1.12.0-beta.1" />
   </ItemGroup>
   <!-- Tests and benchmarks -->
@@ -96,4 +102,4 @@
     <PackageVersion Include="CNinnovation.Codebreaker.Cosmos" Version="3.9.0" />
     <PackageVersion Include="CNinnovation.Codebreaker.SqlServer" Version="3.9.0" />
   </ItemGroup>
-</Project>
+</Project>

ch13/AsyncStreamingChannels/AsyncStreamingChannels.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

ch13/AsyncStreamingChannels/Program.cs

@@ -0,0 +1,154 @@
+// Source code for: Expert CSharp Programming.
+// Author: Christian Nagel.
+// Licensed under the MIT License.
+
+using System.Diagnostics;
+using System.Text;
+using System.Threading.Channels;
+
+Console.OutputEncoding = Encoding.UTF8;
+
+// =====================================================
+// System.Threading.Channels – fan-out pub/sub news feed
+// =====================================================
+Console.WriteLine("System.Threading.Channels – Fan-Out Pub/Sub News Feed");
+Console.WriteLine("-----------------------------------------------------");
+
+// Ingestion channel: two publishers write here (bounded, backpressure-aware)
+var ingestChannel = Channel.CreateBounded<NewsArticle>(
+    new BoundedChannelOptions(20)
+    {
+        FullMode = BoundedChannelFullMode.Wait,
+        SingleWriter = false,   // two publishers
+        SingleReader = true,    // one dispatcher reads and fans out
+    });
+
+// Per-subscriber channels (unbounded – dispatcher controls pacing)
+var techChannel = Channel.CreateUnbounded<NewsArticle>();
+var financeChannel = Channel.CreateUnbounded<NewsArticle>();
+
+var ingestWriter = ingestChannel.Writer;
+
+// Two publishers – simulating different news sources
+Task publisher1 = PublishNewsAsync("Reuters", ingestWriter, 5, delay: 100);
+Task publisher2 = PublishNewsAsync("Bloomberg", ingestWriter, 5, delay: 150);
+
+// Dispatcher: routes each article to matching subscriber channels
+Task dispatcher = DispatchNewsAsync(
+    ingestChannel.Reader,
+    new NewsSubscription("Tech", techChannel.Writer),
+    new NewsSubscription("Finance", financeChannel.Writer));
+
+// Two independent subscribers – each receives only its category stream
+Task consumer1 = ConsumeNewsAsync("Subscriber-A [Tech]", techChannel.Reader);
+Task consumer2 = ConsumeNewsAsync("Subscriber-B [Finance]", financeChannel.Reader);
+
+// Wait for publishers, complete the ingestion channel, then drain everything
+await Task.WhenAll(publisher1, publisher2);
+ingestWriter.Complete();
+await dispatcher;
+await Task.WhenAll(consumer1, consumer2);
+Console.WriteLine();
+
+static async Task DispatchNewsAsync(
+    ChannelReader<NewsArticle> source,
+    params NewsSubscription[] subscribers)
+{
+    ArgumentNullException.ThrowIfNull(source);
+    ArgumentNullException.ThrowIfNull(subscribers);
+
+    try
+    {
+        // Topic routing: each article is forwarded only to matching subscribers
+        await foreach (NewsArticle article in source.ReadAllAsync())
+        {
+            foreach (NewsSubscription subscriber in subscribers)
+            {
+                if (article.Category != subscriber.Category) continue;
+                await subscriber.Writer.WriteAsync(article);
+            }
+        }
+    }
+    finally
+    {
+        foreach (NewsSubscription subscriber in subscribers)
+            subscriber.Writer.Complete();
+    }
+}
+
+static async Task PublishNewsAsync(
+    string source,
+    ChannelWriter<NewsArticle> channelWriter,
+    int count,
+    int delay)
+{
+    string[] categories = ["Tech", "Finance", "Sports", "Politics"];
+
+    for (int i = 1; i <= count; i++)
+    {
+        NewsArticle article = new(
+            Id: $"{source}-{i:000}",
+            Headline: $"{source} headline #{i}",
+            Category: categories[Random.Shared.Next(categories.Length)],
+            PublishedAt: DateTimeOffset.UtcNow);
+
+        await channelWriter.WriteAsync(article);
+        Console.WriteLine($"Published [{article.Id}] {article.Headline} ({article.Category})");
+        await Task.Delay(delay);
+    }
+}
+
+static async Task ConsumeNewsAsync(
+    string consumerName,
+    ChannelReader<NewsArticle> channelReader)
+{
+    await foreach (NewsArticle article in channelReader.ReadAllAsync())
+    {
+        Console.WriteLine($" {consumerName}: [{article.Id}] {article.Headline}");
+        await Task.Delay(20); // simulate processing
+    }
+}
+
+// ==============================================
+// Channels – performance: throughput measurement
+// ==============================================
+Console.WriteLine("Channel Throughput Benchmark");
+Console.WriteLine("----------------------------");
+
+const int MessageCount = 100_000;
+Channel<int> benchChannel = Channel.CreateUnbounded<int>(
+    new UnboundedChannelOptions { SingleWriter = true, SingleReader = true });
+
+Stopwatch sw = Stopwatch.StartNew();
+
+Task producer = Task.Run(async () =>
+{
+    for (int i = 0; i < MessageCount; i++)
+        await benchChannel.Writer.WriteAsync(i);
+    benchChannel.Writer.Complete();
+});
+
+int received = 0;
+Task consumer = Task.Run(async () =>
+{
+    await foreach (int _ in benchChannel.Reader.ReadAllAsync())
+        received++;
+});
+
+await Task.WhenAll(producer, consumer);
+sw.Stop();
+
+double throughputPerSec = MessageCount / (sw.Elapsed.TotalSeconds);
+Console.WriteLine($"{MessageCount:N0} messages in {sw.ElapsedMilliseconds} ms");
+Console.WriteLine($"Throughput: {throughputPerSec:N0} messages/sec");
+Console.WriteLine();
+
+// ============================================================
+// Domain types
+// ============================================================
+
+sealed record StockTick(string Symbol, decimal Price, DateTimeOffset Timestamp);
+
+sealed record NewsSubscription(string Category, ChannelWriter<NewsArticle> Writer);
+
+sealed record NewsArticle(string Id, string Headline, string Category, DateTimeOffset PublishedAt);

ch13/Common/Blazor.ServiceDefaults/BackgroundExportHandler.cs

@@ -0,0 +1,133 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Net;
+using System.Net.Http.Headers;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Polly;
+
+namespace Blazor.ServiceDefaults;
+
+/// <summary>
+/// A DelegatingHandler that works around the OTel SDK's sync-over-async
+/// deadlock on WASM. The SDK calls SendAsync().GetAwaiter().GetResult()
+/// in OtlpExportClient.SendHttpRequest(), which blocks the single WASM
+/// thread. This handler returns 200 immediately to unblock the SDK,
+/// then sends the real request with retries in the background.
+/// </summary>
+internal sealed class BackgroundExportHandler(
+    ResiliencePipeline<HttpResponseMessage> pipeline,
+    IServiceProvider serviceProvider) : DelegatingHandler(new HttpClientHandler())
+{
+    private ILogger? _logger;
+    private ILogger Logger => _logger ??= serviceProvider.GetRequiredService<ILoggerFactory>().CreateLogger("Aspire.OtlpExport");
+
+    protected override Task<HttpResponseMessage> SendAsync(
+        HttpRequestMessage request, CancellationToken cancellationToken)
+    {
+        // Capture request data before returning — the SDK disposes the
+        // HttpRequestMessage via 'using' after .GetResult() completes.
+        var snapshot = RequestSnapshot.Capture(request);
+
+        // Send the real request with retries in the background.
+        _ = SendWithRetryAsync(snapshot, CancellationToken.None);
+
+        // Return 200 immediately so the SDK's sync .GetResult() unblocks.
+        return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK));
+    }
+
+    private async Task SendWithRetryAsync(
+        RequestSnapshot snapshot, CancellationToken cancellationToken)
+    {
+        try
+        {
+            var response = await pipeline.ExecuteAsync(async token =>
+            {
+                using var clone = snapshot.CreateRequest();
+                return await base.SendAsync(clone, token).ConfigureAwait(false);
+            }, cancellationToken).ConfigureAwait(false);
+
+            if (!response.IsSuccessStatusCode)
+            {
+                Logger.LogWarning(
+                    "OTLP export to {Uri} completed with status {StatusCode} after retries.",
+                    snapshot.RequestUri, response.StatusCode);
+            }
+
+            response.Dispose();
+        }
+        catch (Exception ex) when (ex is not OperationCanceledException)
+        {
+            Logger.LogWarning(ex,
+                "OTLP export to {Uri} failed after retries.", snapshot.RequestUri);
+        }
+    }
+}
+
+/// <summary>
+/// Captures the essential parts of an HttpRequestMessage so it can be
+/// cloned for each retry attempt after the original request is disposed
+/// by the SDK. The OTLP SDK always sends ByteArrayContent (protobuf),
+/// so ReadAsByteArrayAsync completes synchronously.
+/// </summary>
+internal sealed class RequestSnapshot
+{
+    public HttpMethod Method { get; init; } = null!;
+    public Uri RequestUri { get; init; } = null!;
+    public List<KeyValuePair<string, IEnumerable<string>>> Headers { get; init; } = null!;
+    public byte[]? ContentBytes { get; init; }
+    public MediaTypeHeaderValue? ContentType { get; init; }
+
+    public static RequestSnapshot Capture(HttpRequestMessage request)
+    {
+        byte[]? contentBytes = null;
+        MediaTypeHeaderValue? contentType = null;
+
+        if (request.Content is not null)
+        {
+            // ByteArrayContent.ReadAsByteArrayAsync completes synchronously
+            // since the bytes are already in memory — safe to .GetResult().
+            contentBytes = request.Content.ReadAsByteArrayAsync()
+                .GetAwaiter().GetResult();
+            contentType = request.Content.Headers.ContentType;
+        }
+
+        // Copy headers since the original request will be disposed.
+        var headers = new List<KeyValuePair<string, IEnumerable<string>>>();
+        foreach (var header in request.Headers)
+        {
+            headers.Add(new(header.Key, [.. header.Value]));
+        }
+
+        return new RequestSnapshot
+        {
+            Method = request.Method,
+            RequestUri = request.RequestUri!,
+            Headers = headers,
+            ContentBytes = contentBytes,
+            ContentType = contentType,
+        };
+    }
+
+    public HttpRequestMessage CreateRequest()
+    {
+        var clone = new HttpRequestMessage(Method, RequestUri);
+
+        foreach (var header in Headers)
+        {
+            clone.Headers.TryAddWithoutValidation(header.Key, header.Value);
+        }
+
+        if (ContentBytes is not null)
+        {
+            clone.Content = new ByteArrayContent(ContentBytes);
+            if (ContentType is not null)
+            {
+                clone.Content.Headers.ContentType = ContentType;
+            }
+        }
+
+        return clone;
+    }
+}

ch13/Common/Blazor.ServiceDefaults/Blazor.ServiceDefaults.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk.Razor">
+
+  <PropertyGroup>
+    <TargetFramework>net11.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <ManagePackageVersionsCentrally>false</ManagePackageVersionsCentrally>
+    <!-- .NET 11 preview needed - don't use CPM until release of .NET 11 -->
+  </PropertyGroup>
+
+  <ItemGroup>
+    <SupportedPlatform Include="browser" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly" Version="11.0.0-preview.7.26381.103" />
+    <PackageReference Include="Microsoft.Extensions.Http.Resilience" Version="10.9.0" />
+    <PackageReference Include="Microsoft.Extensions.ServiceDiscovery" Version="10.9.0" />
+    <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.18.0" />
+    <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.18.0" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.Http" Version="1.18.0" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.Runtime" Version="1.18.0" />
+  </ItemGroup>
+
+</Project>