Initial commit: companion code for all 32 chapters (Parts I-VII, 152 tests passing)

Author: NinjaRocks

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+    branches: [ main, master ]
+    paths:
+      - 'Code/**'
+      - 'References/**'
+      - '.github/workflows/ci.yml'
+  pull_request:
+    branches: [ main, master ]
+    paths:
+      - 'Code/**'
+      - 'References/**'
+      - '.github/workflows/ci.yml'
+
+jobs:
+  build-and-test:
+    name: Build & Test — All Parts
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup .NET 9
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '9.0.x'
+
+      - name: Restore dependencies
+        run: dotnet restore Code/BankAccount.sln
+
+      - name: Build
+        run: dotnet build Code/BankAccount.sln --no-restore --configuration Release
+
+      - name: Test — Part I (Thinking in Domains, Ch 1–6)
+        run: dotnet test Code/Part-I/Part-I.sln --no-build --configuration Release --logger "trx;LogFileName=part-i-results.trx" --results-directory ./test-results
+        continue-on-error: false
+
+      - name: Test — Part II (Modelling with Events, Ch 7–11)
+        run: dotnet test Code/Part-II/Part-II.sln --no-build --configuration Release --logger "trx;LogFileName=part-ii-results.trx" --results-directory ./test-results
+        continue-on-error: false
+
+      - name: Test — Part III (Commanding Change, Ch 12–16)
+        run: dotnet test Code/Part-III/Part-III.sln --no-build --configuration Release --logger "trx;LogFileName=part-iii-results.trx" --results-directory ./test-results
+        continue-on-error: false
+
+      - name: Test — Part IV (Reading the World, Ch 17–22)
+        run: dotnet test Code/Part-IV/Part-IV.sln --no-build --configuration Release --logger "trx;LogFileName=part-iv-results.trx" --results-directory ./test-results
+        continue-on-error: false
+
+      - name: Test — Part V (Infrastructure & Persistence, Ch 23–26)
+        run: dotnet test Code/Part-V/Part-V.sln --no-build --configuration Release --logger "trx;LogFileName=part-v-results.trx" --results-directory ./test-results
+        continue-on-error: false
+
+      - name: Test — Part VI (Production Readiness, Ch 27–29)
+        run: dotnet test Code/Part-VI/Part-VI.sln --no-build --configuration Release --logger "trx;LogFileName=part-vi-results.trx" --results-directory ./test-results
+        continue-on-error: false
+
+      - name: Test — Part VII (Inside the Framework, Ch 30–32)
+        run: dotnet test Code/Part-VII/Part-VII.sln --no-build --configuration Release --logger "trx;LogFileName=part-vii-results.trx" --results-directory ./test-results
+        continue-on-error: false
+
+      - name: Upload test results
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: test-results
+          path: ./test-results/*.trx
+          retention-days: 30
+
+  build-summary:
+    name: Summary
+    runs-on: ubuntu-latest
+    needs: build-and-test
+    if: always()
+    steps:
+      - name: Report status
+        run: |
+          if [ "${{ needs.build-and-test.result }}" == "success" ]; then
+            echo "✅ All 7 parts built and 152 tests passed."
+          else
+            echo "❌ Build or tests failed. Check the build-and-test job for details."
+            exit 1
+          fi

.gitignore

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+# .gitignore for DDD Event Sourcing companion code repository
+
+# Build outputs
+bin/
+obj/
+
+# Visual Studio
+.vs/
+*.user
+*.suo
+*.userosscache
+*.sln.docstates
+
+# Rider
+.idea/
+
+# Test results
+TestResults/
+*.trx
+*.coverage
+*.coveragexml
+
+# NuGet
+*.nupkg
+*.snupkg
+packages/
+project.lock.json
+project.fragment.lock.json
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Docker
+docker-compose.override.yml

BankAccount.sln

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+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31903.59
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{9EA39149-7870-4C27-A7CD-DC130BF09635}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "tests", "tests", "{5C75626C-2652-4AF3-B133-E12D4EDDB5FE}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "BankAccount.Domain", "src\BankAccount.Domain\BankAccount.Domain.csproj", "{9B1729DB-4FBB-4A56-96DE-3290BBE5017B}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "BankAccount.Domain.Tests", "tests\BankAccount.Domain.Tests\BankAccount.Domain.Tests.csproj", "{AD39EDD9-8D14-4316-B6B8-A0955CDBD7FE}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{9B1729DB-4FBB-4A56-96DE-3290BBE5017B}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{9B1729DB-4FBB-4A56-96DE-3290BBE5017B}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{9B1729DB-4FBB-4A56-96DE-3290BBE5017B}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{9B1729DB-4FBB-4A56-96DE-3290BBE5017B}.Release|Any CPU.Build.0 = Release|Any CPU
+		{AD39EDD9-8D14-4316-B6B8-A0955CDBD7FE}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{AD39EDD9-8D14-4316-B6B8-A0955CDBD7FE}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{AD39EDD9-8D14-4316-B6B8-A0955CDBD7FE}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{AD39EDD9-8D14-4316-B6B8-A0955CDBD7FE}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(NestedProjects) = preSolution
+		{9B1729DB-4FBB-4A56-96DE-3290BBE5017B} = {9EA39149-7870-4C27-A7CD-DC130BF09635}
+		{AD39EDD9-8D14-4316-B6B8-A0955CDBD7FE} = {5C75626C-2652-4AF3-B133-E12D4EDDB5FE}
+	EndGlobalSection
+EndGlobal

Part-I/Part-I.sln

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+// File: BankAccount.Domain/AccountId.cs
+#nullable enable
+
+namespace BankAccount.Domain;
+
+/// <summary>
+/// The identity of a bank account.
+/// An AccountId is a Value Object — two AccountIds with the same Value are equal.
+/// The distinction between a transient (not yet persisted) account and a persisted
+/// account is captured by <see cref="IsTransient"/> rather than by checking for zero
+/// throughout the codebase.
+/// </summary>
+/// <param name="Value">The underlying integer identifier. Zero represents a transient account.</param>
+public record AccountId(int Value)
+{
+    /// <summary>
+    /// Returns true if this AccountId has not yet been assigned by the persistence layer.
+    /// A transient account has not been saved and does not have a database-generated identifier.
+    /// </summary>
+    public bool IsTransient => Value <= 0;
+
+    /// <summary>
+    /// Creates an AccountId representing a new, not-yet-persisted account.
+    /// </summary>
+    public static AccountId Transient() => new(0);
+
+    /// <summary>
+    /// Creates an AccountId from a known persisted value.
+    /// </summary>
+    /// <param name="value">The persisted identifier. Must be positive.</param>
+    /// <exception cref="ArgumentOutOfRangeException">Thrown if value is not positive.</exception>
+    public static AccountId From(int value)
+    {
+        if (value <= 0)
+            throw new ArgumentOutOfRangeException(nameof(value),
+                $"A persisted AccountId must be positive. Received: {value}");
+        return new(value);
+    }
+
+    /// <summary>Returns a string representation, e.g. "AccountId(42)".</summary>
+    public override string ToString() => IsTransient ? "AccountId(transient)" : $"AccountId({Value})";
+}

Part-I/src/BankAccount.Domain/AccountId.cs

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+// File: BankAccount.Domain/AccountNumber.cs
+#nullable enable
+
+using System.Text.RegularExpressions;
+
+namespace BankAccount.Domain;
+
+/// <summary>
+/// A bank account number. This is a Value Object that enforces the account number
+/// format rule: all account numbers in our system start with "ACC-" followed by
+/// one or more digits. An AccountNumber that violates this rule cannot be constructed.
+/// </summary>
+public record AccountNumber
+{
+    private static readonly Regex ValidPattern = new(@"^ACC-\d+$", RegexOptions.Compiled);
+
+    /// <summary>The formatted account number string.</summary>
+    public string Value { get; }
+
+    /// <summary>
+    /// Constructs an AccountNumber, validating the format.
+    /// This is a non-positional record with a single constructor that
+    /// validates its argument before assigning the property — the standard
+    /// C# pattern for value objects that require invariant checking at creation time.
+    /// </summary>
+    /// <param name="value">The account number string to validate and wrap.</param>
+    /// <exception cref="ArgumentException">Thrown if the format is invalid.</exception>
+    public AccountNumber(string value)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+            throw new ArgumentException(
+                "Account number cannot be empty or whitespace.", nameof(value));
+
+        if (!ValidPattern.IsMatch(value))
+            throw new ArgumentException(
+                $"Account number '{value}' does not match the required format 'ACC-<digits>'.",
+                nameof(value));
+
+        Value = value;
+    }
+
+    /// <summary>Returns the account number string.</summary>
+    public override string ToString() => Value;
+}

Part-I/src/BankAccount.Domain/AccountNumber.cs

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+// File: BankAccount.Domain/AccountsContext/AccountCreditApplicationService.cs
+#nullable enable
+
+using BankAccount.Domain;
+using BankAccount.Domain.NotificationsContext;
+
+namespace BankAccount.Domain.AccountsContext;
+
+/// <summary>
+/// An application service that orchestrates the credit operation and the resulting
+/// notification. This is the only place where both contexts meet — and they meet
+/// at the boundary, not inside either context's domain model.
+/// </summary>
+public sealed class AccountCreditApplicationService
+{
+    private readonly BankAccountService _accountService;
+    private readonly AccountNotificationAdapter _adapter;
+    private readonly INotificationSender _notifications;
+
+    /// <summary>Initialises the application service with its dependencies.</summary>
+    public AccountCreditApplicationService(
+        BankAccountService accountService,
+        AccountNotificationAdapter adapter,
+        INotificationSender notifications)
+    {
+        _accountService = accountService;
+        _adapter = adapter;
+        _notifications = notifications;
+    }
+
+    /// <summary>
+    /// Credits an account and dispatches a notification to the account holder.
+    /// The credit operation is a pure Accounts concern.
+    /// The notification is translated at the boundary before dispatch.
+    /// </summary>
+    /// <param name="accountId">The account to credit.</param>
+    /// <param name="amount">The amount to credit.</param>
+    /// <param name="holder">The account holder, used to construct the notification target.</param>
+    public async Task CreditAndNotify(int accountId, Money amount, AccountHolder holder)
+    {
+        await _accountService.CreditAccount(accountId, amount);
+
+        var target = _adapter.ToNotificationTarget(holder);
+        var notification = new AccountCreditedNotification(
+            Target: target,
+            CreditedAmount: amount.ToString(),
+            // Note: CreditAndNotify cannot easily provide the updated balance without
+            // re-querying the repository or changing CreditAccount's return type.
+            // This is a limitation of the current design that the domain event pattern
+            // in Chapter 6 resolves: the AccountCredited event carries NewBalance directly
+            // from the aggregate, eliminating the need for a second query.
+            NewBalance: "See account statement",
+            OccurredOn: DateTime.UtcNow);
+
+        await _notifications.SendCreditNotification(notification);
+    }
+}

Part-I/src/BankAccount.Domain/AccountsContext/AccountCreditApplicationService.cs

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+// File: BankAccount.Domain/AccountsContext/AccountHolder.cs
+#nullable enable
+
+namespace BankAccount.Domain.AccountsContext;
+
+/// <summary>
+/// The Accounts context's model of an account holder.
+/// This is NOT a customer in the CRM sense — it is specifically the person
+/// who holds a bank account in our Accounts bounded context.
+/// It contains only the information the Accounts context needs.
+/// </summary>
+/// <param name="FullName">The account holder's full legal name.</param>
+/// <param name="AccountNumber">The account number associated with this holder.</param>
+public record AccountHolder(string FullName, string AccountNumber);

Part-I/src/BankAccount.Domain/AccountsContext/AccountHolder.cs

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <LangVersion>latest</LangVersion>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>