A lot of comments.

ServiceOne.cs

@@ -1,20 +1,31 @@
 using System;
 
-namespace Playground
+namespace SmallInjectorDemo
 {
+    /// <summary>
+    /// Implementation of <see cref="IServiceOne"/>.
+    /// </summary>
     public class ServiceOne : IServiceOne
     {
+        private const string MyName = nameof(ServiceOne);
         private readonly Guid _guid;
 
+        /// <summary>
+        /// Creates a new instance of <see cref="ServiceOne"/>.
+        /// </summary>
         public ServiceOne()
         {
             _guid = Guid.NewGuid();
-            Console.WriteLine(nameof(ServiceOne) + ".ctor\t\tId: " + _guid);
+            Console.WriteLine(MyName + ".ctor\t\tId: " + _guid);
         }
 
-        public override string ToString() => nameof(ServiceOne) + ".ToString()\tId: " + _guid;
+        /// <inheritdoc />
+        public override string ToString() => MyName + ".ToString()\tId: " + _guid;
     }
 
+    /// <summary>
+    /// Interface for service one.
+    /// </summary>
     public interface IServiceOne
     {