add fp2 sample

csharp-fp2/Infrastructure/InMemoryAccount.cs

@@ -0,0 +1,41 @@
+using CsharpFp2.Domain;
+
+namespace CsharpFp2.Infrastructure;
+
+// If we don't like working with generic delegates directly, we can
+// create custom named delegate types.
+public delegate Account? LoadAccount(Guid id);
+
+public delegate void SaveAccount(Account accunt);
+
+// If we don't want to use tuples, or you really miss the idea of a combined "interface",
+// we can create a named container
+//   public sealed record AccountPersistence(LoadAccount Load, SaveAccount Save);
+
+public static class InMemoryAccount
+{
+    public static (LoadAccount, SaveAccount) Create()
+    {
+        Dictionary<Guid, Account> store = new();
+
+        Account? GetById(Guid id)
+        {
+            var found = store.TryGetValue(id, out var account);
+            Console.WriteLine(
+                found ? $"[Repo] Loaded account {id}" : $"[Repo] Account {id} not found"
+            );
+
+            return found ? account : null;
+        }
+
+        void Save(Account account)
+        {
+            store[account.Id] = account;
+            Console.WriteLine(
+                $"[Repo] Saved account {account.Id} with balance {account.Balance.Amount:0.00}"
+            );
+        }
+
+        return (GetById, Save);
+    }
+}