Improve JSON deserialization and observable collection handling

- Add batch update support for IAcObservableCollection during deserialization to suppress per-item notifications and fire a single reset event.
- Throw AcJsonDeserializationException with a clear message if a type lacks a parameterless constructor during deserialization.
- Enhance IsGenericCollectionType to recognize more collection types, including ObservableCollection<T> and custom IList<T> implementations.
- Improve array and collection deserialization logic to better handle target types and fall back to List<T> if needed.
- In AcObservableCollection, catch and ignore ObjectDisposedException in event handlers to prevent errors from disposed subscribers.
- Remove redundant batch update logic from AcSignalRDataSource; rely on deserializer's handling.
- Set SkipNegotiation = true in SignalR client options for WebSockets-only optimization and comment out automatic HubConnection.StartAsync() for more controlled connection management.

AyCode.Core/Extensions/AcJsonDeserializer.cs

@@ -5,6 +5,7 @@ using System.Linq.Expressions;
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Text.Json;
+using AyCode.Core.Helpers;
 using AyCode.Core.Interfaces;
 using Newtonsoft.Json;
 
@@ -308,7 +309,27 @@ public static class AcJsonDeserializer
         }
 
         var metadata = GetTypeMetadata(targetType);
-        var instance = metadata.CompiledConstructor?.Invoke() ?? Activator.CreateInstance(targetType);
+        
+        object? instance;
+        if (metadata.CompiledConstructor != null)
+        {
+            instance = metadata.CompiledConstructor.Invoke();
+        }
+        else
+        {
+            try
+            {
+                instance = Activator.CreateInstance(targetType);
+            }
+            catch (MissingMethodException ex)
+            {
+                throw new AcJsonDeserializationException(
+                    $"Cannot deserialize type '{targetType.FullName}' because it does not have a parameterless constructor. " +
+                    $"Add a parameterless constructor or use a different serialization approach.",
+                    null, targetType, ex);
+            }
+        }
+        
         if (instance == null) return null;
 
         if (element.TryGetProperty("$id", out var idElement))
@@ -425,9 +446,15 @@ public static class AcJsonDeserializer
 
     private static void PopulateList(JsonElement arrayElement, IList targetList, Type listType, DeserializationContext context)
     {
-        var elementType = GetListElementType(listType);
+        var elementType = GetCollectionElementType(listType);
         if (elementType == null) return;
         
+        // Use batch update for IAcObservableCollection to suppress per-item notifications
+        var acObservable = targetList as IAcObservableCollection;
+        acObservable?.BeginUpdate();
+
+        try
+        {
             targetList.Clear();
             
             foreach (var item in arrayElement.EnumerateArray())
@@ -439,6 +466,11 @@ public static class AcJsonDeserializer
                 }
             }
         }
+        finally
+        {
+            acObservable?.EndUpdate();
+        }
+    }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private static object? ReadArray(JsonElement element, Type targetType, DeserializationContext context)
@@ -446,21 +478,55 @@ public static class AcJsonDeserializer
         var elementType = GetCollectionElementType(targetType);
         if (elementType == null) return null;
 
+        // For arrays, we need to use a temporary list
+        if (targetType.IsArray)
+        {
             var list = GetOrCreateListFactory(elementType)();
-
             foreach (var item in element.EnumerateArray())
             {
                 list.Add(ReadValue(item, elementType, context));
             }
-
-        if (targetType.IsArray)
-        {
             var array = Array.CreateInstance(elementType, list.Count);
             list.CopyTo(array, 0);
             return array;
         }
 
-        return list;
+        // Try to create an instance of the target collection type directly
+        // This handles ObservableCollection<T>, AcObservableCollection<T>, etc.
+        IList? targetList = null;
+        try
+        {
+            var instance = Activator.CreateInstance(targetType);
+            if (instance is IList list)
+            {
+                targetList = list;
+            }
+        }
+        catch
+        {
+            // Fallback to List<T> if we can't create the target type
+        }
+        
+        // Fallback to List<T> if target type couldn't be instantiated
+        targetList ??= GetOrCreateListFactory(elementType)();
+
+        // Use batch update for IAcObservableCollection to suppress per-item notifications
+        var acObservable = targetList as IAcObservableCollection;
+        acObservable?.BeginUpdate();
+
+        try
+        {
+            foreach (var item in element.EnumerateArray())
+            {
+                targetList.Add(ReadValue(item, elementType, context));
+            }
+        }
+        finally
+        {
+            acObservable?.EndUpdate();
+        }
+
+        return targetList;
     }
 
     private static void MergeIIdCollection(JsonElement arrayElement, object existingCollection, PropertySetterInfo propInfo, DeserializationContext context)
@@ -472,6 +538,12 @@ public static class AcJsonDeserializer
         var existingList = (IList)existingCollection;
         var count = existingList.Count;
         
+        // Use batch update for IAcObservableCollection to suppress per-item notifications
+        var acObservable = existingList as IAcObservableCollection;
+        acObservable?.BeginUpdate();
+
+        try
+        {
             Dictionary<object, object>? existingById = null;
             if (count > 0)
             {
@@ -515,6 +587,11 @@ public static class AcJsonDeserializer
                 if (newItem != null) existingList.Add(newItem);
             }
         }
+        finally
+        {
+            acObservable?.EndUpdate();
+        }
+    }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private static object? ReadPrimitive(JsonElement element, Type targetType, JsonValueKind valueKind)
@@ -1038,18 +1115,43 @@ public static class AcJsonDeserializer
     }
 
     /// <summary>
-    /// Check if type is a generic collection type (List, IList, etc.)
+    /// Check if type is a generic collection type (List, IList, ObservableCollection, etc.)
     /// </summary>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private static bool IsGenericCollectionType(Type type)
     {
-        if (!type.IsGenericType) return false;
+        if (!type.IsGenericType)
+        {
+            // Check if it implements IList<T> interface (covers ObservableCollection<T> subclasses)
+            foreach (var iface in type.GetInterfaces())
+            {
+                if (iface.IsGenericType && iface.GetGenericTypeDefinition() == typeof(IList<>))
+                    return true;
+            }
+            return false;
+        }
         
         var genericDef = type.GetGenericTypeDefinition();
-        return genericDef == typeof(List<>) || 
+        
+        // Check common collection types
+        if (genericDef == typeof(List<>) || 
             genericDef == typeof(IList<>) || 
             genericDef == typeof(ICollection<>) || 
-               genericDef == typeof(IEnumerable<>);
+            genericDef == typeof(IEnumerable<>) ||
+            genericDef == typeof(System.Collections.ObjectModel.ObservableCollection<>) ||
+            genericDef == typeof(System.Collections.ObjectModel.Collection<>))
+        {
+            return true;
+        }
+        
+        // Check if it implements IList<T> interface (covers AcObservableCollection<T> and similar)
+        foreach (var iface in type.GetInterfaces())
+        {
+            if (iface.IsGenericType && iface.GetGenericTypeDefinition() == typeof(IList<>))
+                return true;
+        }
+        
+        return false;
     }
     #endregion
 }

AyCode.Core/Helpers/AcObservableCollection.cs

@@ -374,18 +374,30 @@ namespace AyCode.Core.Helpers
 
         protected override void OnPropertyChanged(PropertyChangedEventArgs e)
         {
-            if (IsUpdating)
+            if (IsUpdating) return;
-                return;
 
+            try
+            {
                 base.OnPropertyChanged(e);
             }
+            catch (ObjectDisposedException)
+            {
+                // A feliratkozott komponens már Disposed - biztonságosan figyelmen kívül hagyjuk
+            }
+        }
 
         protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
         {
-            if (IsUpdating)
+            if (IsUpdating) return;
-                return;
 
+            try
+            {
                 base.OnCollectionChanged(e);
             }
+            catch (ObjectDisposedException)
+            {
+                // A feliratkozott komponens már Disposed - biztonságosan figyelmen kívül hagyjuk
+            }
+        }
     }
 }

AyCode.Services.Server/SignalRs/AcSignalRDataSource.cs

@@ -353,13 +353,9 @@ namespace AyCode.Services.Server.SignalRs
                 {
                     if (!setSourceToWorkingReferenceList)
                     {
-                        if (InnerList is IAcObservableCollection observable)
+                        // CopyTo uses JSON serialization which already handles BeginUpdate/EndUpdate
-                        {
+                        // for IAcObservableCollection via AcJsonDeserializer.Populate
-                            observable.BeginUpdate();
                         fromSource.CopyTo(InnerList);
-                            observable.EndUpdate();
-                        }
-                        else fromSource.CopyTo(InnerList);
                     }
                     else
                     {

AyCode.Services/SignalRs/AcSignalRClientBase.cs

@@ -46,6 +46,7 @@ namespace AyCode.Services.SignalRs
                         options.TransportMaxBufferSize = 30_000_000; //Increasing this value allows the client to receive larger messages. default: 65KB; unlimited: 0;;
                         options.ApplicationMaxBufferSize = 30_000_000; //Increasing this value allows the client to send larger messages. default: 65KB; unlimited: 0;
                         options.CloseTimeout = TimeSpan.FromSeconds(10); //default: 5 sec.
+                        options.SkipNegotiation = true; // Skip HTTP negotiation when using WebSockets only
 
                         //options.AccessTokenProvider = null;
                         //options.HttpMessageHandlerFactory = null;
@@ -82,7 +83,7 @@ namespace AyCode.Services.SignalRs
             _ = HubConnection.On<int, byte[], int?>(nameof(IAcSignalRHubClient.OnReceiveMessage), OnReceiveMessage);
             //_ = HubConnection.On<int, int>(nameof(IAcSignalRHubClient.OnRequestMessage), OnRequestMessage);
 
-            HubConnection.StartAsync().Forget();
+            //HubConnection.StartAsync().Forget();
         }
 
         /// <summary>