Демка с чатом работает

Example.Events.Backend/Chat.cs

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+using Example.Events.Shared;
+using mROA.Implementation;
+
+namespace Example.Events.Backend;
+
+public class Chat : IChat
+{
+    public void PostSymbol(string symbol, RequestContext context)
+    {
+        OnCharPosted?.Invoke(symbol, context);
+    }
+
+    public event Action<string, RequestContext>? OnCharPosted;
+
+    public void OnCharPostedExternal(string p0, RequestContext p1)
+    {
+    }
+}

Example.Events.Backend/ChatFactory.cs

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+using Example.Events.Shared;
+using mROA.Implementation.Attributes;
+
+namespace Example.Events.Backend;
+
+[SharedObjectSingleton]
+public class ChatFactory : IChatFactory
+{
+    private static readonly Dictionary<Guid, IChat> Chats = new();
+
+    public IChat GetChat(Guid id)
+    {
+        if (Chats.TryGetValue(id, out var chat))
+        {
+            return chat;
+        }
+
+        var created = new Chat();
+        Chats.Add(id, created);
+        return created;
+    }
+}