Add code examples, and documentation

patterns/memento/MementoPattern/Originator.cs

@@ -0,0 +1,46 @@
+namespace MementoPattern;
+
+public class Originator : IOriginator
+{
+   private Guid _id;
+
+   public Originator()
+   {
+      _id = Guid.NewGuid();
+      Console.WriteLine($"Starting ID: {_id}");
+      Console.WriteLine();
+   }
+
+   public IMemento GetMemento()
+   {
+      Memento memento = new Memento();
+      memento.Id = _id;
+      Console.WriteLine("Creating Memento...");
+      Console.WriteLine();
+      return memento;
+   }
+
+   public void SetMemento(IMemento memento)
+   {
+      if (!(memento is Memento))
+         return;
+      Console.WriteLine("Restting ID...");
+      _id = (memento as Memento).Id;
+
+      Console.WriteLine($"ID is reset to {_id}");
+      Console.WriteLine();
+   }
+
+   public void UpdateId()
+   {
+      Console.WriteLine("Updating Id...");
+      _id = Guid.NewGuid();
+      Console.WriteLine($"Updated ID is now {_id}");
+      Console.WriteLine();
+   }
+
+   private class Memento : IMemento
+   {
+      public Guid Id;
+   }
+}