Try use ordered set for recent songs

TaikoLocalServer/Common/OrderedSet.cs

@@ -0,0 +1,73 @@
+using System.Collections;
+
+namespace TaikoLocalServer.Common;
+
+public class OrderedSet<T> : ICollection<T> where T : notnull
+{
+    private readonly IDictionary<T, LinkedListNode<T>> dictionary;
+    private readonly LinkedList<T> linkedList;
+
+    public OrderedSet()
+        : this(EqualityComparer<T>.Default)
+    {
+    }
+
+    public OrderedSet(IEqualityComparer<T> comparer)
+    {
+        dictionary = new Dictionary<T, LinkedListNode<T>>(comparer);
+        linkedList = new LinkedList<T>();
+    }
+
+    public int Count => dictionary.Count;
+
+    public virtual bool IsReadOnly => dictionary.IsReadOnly;
+
+    void ICollection<T>.Add(T item)
+    {
+        Add(item);
+    }
+
+    public bool Add(T item)
+    {
+        if (dictionary.ContainsKey(item)) return false;
+        var node = linkedList.AddLast(item);
+        dictionary.Add(item, node);
+        return true;
+    }
+
+    public void Clear()
+    {
+        linkedList.Clear();
+        dictionary.Clear();
+    }
+
+    public bool Remove(T? item)
+    {
+        if (item == null) return false;
+        var found = dictionary.TryGetValue(item, out var node);
+        if (!found) return false;
+        dictionary.Remove(item);
+        if (node != null) linkedList.Remove(node);
+        return true;
+    }
+
+    public IEnumerator<T> GetEnumerator()
+    {
+        return linkedList.GetEnumerator();
+    }
+
+    IEnumerator IEnumerable.GetEnumerator()
+    {
+        return GetEnumerator();
+    }
+
+    public bool Contains(T? item)
+    {
+        return item != null && dictionary.ContainsKey(item);
+    }
+
+    public void CopyTo(T[] array, int arrayIndex)
+    {
+        linkedList.CopyTo(array, arrayIndex);
+    }
+}

TaikoLocalServer/Controllers/Game/UserDataController.cs

@@ -51,8 +51,8 @@ public class UserDataController : BaseController<UserDataController>
             .Select(datum => datum.SongId)
             .ToArray();
         
-        // Use custom implementation as distictby cannot guarantee preserved element
-        var recentSet = new SortedSet<uint>();
+        // Use custom implementation as distinctby cannot guarantee preserved element
+        var recentSet = new OrderedSet<uint>();
         foreach (var id in recentSongs)
         {
             recentSet.Add(id);
@@ -103,8 +103,6 @@ public class UserDataController : BaseController<UserDataController>
             AryRecentSongNoes = recentSongs,
             NotesPosition = userData.NotesPosition
         };
-        
-        
 
         return Ok(response);
     }