diff --git a/fundamentals/aot/diagnostics/Rdg9/Program.cs b/fundamentals/aot/diagnostics/Rdg9/Program.cs
new file mode 100644
index 0000000..da29dc2
--- /dev/null
+++ b/fundamentals/aot/diagnostics/Rdg9/Program.cs
@@ -0,0 +1,95 @@
+#define RDG009 //RDG009F
+#if NEVER
+#elif RDG009
+// <snippet_1>
+using System.Text.Json.Serialization;
+
+var builder = WebApplication.CreateSlimBuilder();
+var todos = new[]
+{
+    new Todo(1, "Write tests", DateTime.UtcNow.AddDays(2)),
+    new Todo(2, "Fix tests",DateTime.UtcNow.AddDays(1))
+};
+builder.Services.AddSingleton(todos);
+builder.Services.ConfigureHttpJsonOptions(options =>
+{
+    options.SerializerOptions.TypeInfoResolverChain.Insert(0, AppJsonSerializerContext.Default);
+});
+
+var app = builder.Build();
+
+
+app.MapGet("/v1/todos/{id}", ([AsParameters] TodoItemRequest request) =>
+{
+    return request.todos.ToList().Find(todoItem => todoItem.Id == request.Id)
+is Todo todo
+    ? Results.Ok(todo)
+    : Results.NotFound();
+});
+
+app.Run();
+
+struct TodoItemRequest
+{
+    public int Id { get; set; }
+
+    [AsParameters]
+    public Todo[] todos { get; set; }
+}
+
+
+internal record Todo(int Id, string Task, DateTime DueDate);
+
+
+[JsonSerializable(typeof(Todo[]))]
+internal partial class AppJsonSerializerContext : JsonSerializerContext
+{
+}
+// </snippet_1>
+
+
+#elif RDG009F
+// <snippet_1f>
+using System.Text.Json.Serialization;
+
+var builder = WebApplication.CreateSlimBuilder();
+var todos = new[]
+{
+    new Todo(1, "Write tests", DateTime.UtcNow.AddDays(2)),
+    new Todo(2, "Fix tests",DateTime.UtcNow.AddDays(1))
+};
+builder.Services.AddSingleton(todos);
+builder.Services.ConfigureHttpJsonOptions(options =>
+{
+    options.SerializerOptions.TypeInfoResolverChain.Insert(0, AppJsonSerializerContext.Default);
+});
+
+var app = builder.Build();
+
+
+app.MapGet("/v1/todos/{id}", ([AsParameters] TodoItemRequest request) =>
+{
+     return request.todos.ToList().Find(todoItem => todoItem.Id == request.Id)
+is Todo todo
+    ? Results.Ok(todo)
+    : Results.NotFound();
+});
+
+app.Run();
+
+struct TodoItemRequest
+{
+    public int Id { get; set; }
+    public Todo[] todos { get; set; }
+}
+
+
+internal record Todo(int Id, string Task, DateTime DueDate);
+
+
+[JsonSerializable(typeof(Todo[]))]
+internal partial class AppJsonSerializerContext : JsonSerializerContext
+{
+}
+// </snippet_1f>
+#endif
diff --git a/fundamentals/aot/diagnostics/Rdg9/Rdg9.csproj b/fundamentals/aot/diagnostics/Rdg9/Rdg9.csproj
new file mode 100644
index 0000000..8186e5b
--- /dev/null
+++ b/fundamentals/aot/diagnostics/Rdg9/Rdg9.csproj
@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <InvariantGlobalization>true</InvariantGlobalization>
+    <PublishAot>true</PublishAot>
+  </PropertyGroup>
+
+</Project>
diff --git a/fundamentals/aot/diagnostics/Rdg9/appsettings.json b/fundamentals/aot/diagnostics/Rdg9/appsettings.json
new file mode 100644
index 0000000..10f68b8
--- /dev/null
+++ b/fundamentals/aot/diagnostics/Rdg9/appsettings.json
@@ -0,0 +1,9 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}