Initial: AI code exploration exercise

src/Before/WebApp.cs

@@ -0,0 +1,40 @@
+namespace Before;
+
+/// <summary>
+/// The consuming application. In the "before" situation it talks to the
+/// DB-backed domain model directly: its methods take <see cref="Client"/> and
+/// <see cref="Order"/> (which inherit <see cref="DbBase"/>) as parameters.
+///
+/// One of its methods reaches the <see cref="DbContext"/> *through* a domain
+/// object — the leak. In the "after" situation (Yak 02) the WebApp consumes
+/// DTOs instead, and the domain objects no longer expose a DbContext.
+/// </summary>
+public class WebApp
+{
+    /// <summary>
+    /// Render a client together with all of its orders, consuming the
+    /// <see cref="Client"/>/ <see cref="Order"/> domain objects directly.
+    /// </summary>
+    public string ShowClient(Client client)
+    {
+        ArgumentNullException.ThrowIfNull(client);
+
+        var lines = new List<string> { $"{client.Name} [{client.Id}]" };
+        foreach (var order in client.Orders)
+            lines.Add($"  - order [{order.Id}]: {order.Description}");
+        return string.Join(Environment.NewLine, lines);
+    }
+
+    /// <summary>
+    /// The leak, made concrete: from a plain domain object the WebApp can reach
+    /// the <see cref="DbContext"/> (<see cref="DbBase.DbContext"/>) and thus
+    /// touch the persistence layer — here just to ask whether the client has
+    /// been saved. The "after" situation removes <c>client.DbContext</c>
+    /// entirely, so no DTO-consumer can do this.
+    /// </summary>
+    public bool IsPersisted(Client client)
+    {
+        ArgumentNullException.ThrowIfNull(client);
+        return client.DbContext is not null;
+    }
+}