Rename because it is ordered

PersistentOrderedMap/TransientOrderedMap.cs

@@ -0,0 +1,40 @@
+using System.Collections;
+
+namespace PersistentOrderedMap;
+
+public sealed class TransientOrderedMap<K, V, TStrategy> : BaseOrderedMap<K, V, TStrategy> where TStrategy : IKeyStrategy<K>
+{
+    // This is mutable, but we treat it as readonly for the ID generation logic usually.
+    private OwnerId _transactionId;
+
+    public TransientOrderedMap(Node<K> root, TStrategy strategy, int count) 
+        : base(root, strategy, count) 
+    {
+        _transactionId = OwnerId.Next();
+    }
+
+    public void Set(K key, V value)
+    {
+        _root = BTreeFunctions.Set(_root, key, value, _strategy, _transactionId, out bool countChanged);
+        if (countChanged) Count++;
+    }
+
+    public void Remove(K key)
+    {
+        _root = BTreeFunctions.Remove<K,V, TStrategy>(_root, key, _strategy, _transactionId, out bool removed);
+        if (removed) Count--;
+    }
+
+    public PersistentOrderedMap<K, V, TStrategy> ToPersistent()
+    {
+        // 1. Create the snapshot by copying all relevant information
+            
+        var snapshot = new PersistentOrderedMap<K, V, TStrategy>(_root, _strategy, Count);
+
+        // 2. Protect the snapshot from THIS TransientOrderedMap by getting a new ownerId 
+        // so that future edits will be done by CoW
+        _transactionId = OwnerId.Next();
+            
+        return snapshot;
+    }
+}