diff --git a/TIAMSharedUI/Pages/User/SysAdmins/ManageTransfers.razor b/TIAMSharedUI/Pages/User/SysAdmins/ManageTransfers.razor
index 6401fa80..8cb19deb 100644
--- a/TIAMSharedUI/Pages/User/SysAdmins/ManageTransfers.razor
+++ b/TIAMSharedUI/Pages/User/SysAdmins/ManageTransfers.razor
@@ -396,7 +396,7 @@
     {
         _logger.Info("DataSourceItemChanged called");
 
-        AppointmentModels.UpdateCollection(CreateAppointmentModel(args.DataItem), args.DataChangeMode == DataChangeMode.Remove);
+        AppointmentModels.UpdateCollection(CreateAppointmentModel(args.DataItem), args.TrackingState == TrackingState.Remove);
     }
 
     private void DataItemSaving(GridEditModelSavingEventArgs e)
diff --git a/TIAMSharedUI/Pages/User/SysAdmins/TransferToDriverGridComponent.razor b/TIAMSharedUI/Pages/User/SysAdmins/TransferToDriverGridComponent.razor
index 4984cf08..83b676ac 100644
--- a/TIAMSharedUI/Pages/User/SysAdmins/TransferToDriverGridComponent.razor
+++ b/TIAMSharedUI/Pages/User/SysAdmins/TransferToDriverGridComponent.razor
@@ -59,7 +59,7 @@
 
     private void DataItemChanged(GridDataItemChangedEventArgs<TransferToDriver> args)
     {
-        ParentData.TransferToDrivers.UpdateCollection(args.DataItem, args.DataChangeMode == DataChangeMode.Remove);
+        ParentData.TransferToDrivers.UpdateCollection(args.DataItem, args.TrackingState == TrackingState.Remove);
 
         OnTransferToDriverChanged.InvokeAsync(args.DataItem);
     }
diff --git a/TIAMSharedUI/Shared/Components/Grids/TiamGrid.cs b/TIAMSharedUI/Shared/Components/Grids/TiamGrid.cs
index 356e92f0..0fc18741 100644
--- a/TIAMSharedUI/Shared/Components/Grids/TiamGrid.cs
+++ b/TIAMSharedUI/Shared/Components/Grids/TiamGrid.cs
@@ -17,7 +17,7 @@ namespace TIAMSharedUI.Shared.Components.Grids
 {
     public class GridDataItemChangingEventArgs<TDataItem> : GridDataItemChangedEventArgs<TDataItem> where TDataItem : class, IId<Guid>
     {
-        internal GridDataItemChangingEventArgs(TiamGrid<TDataItem> grid, TDataItem dataItem, DataChangeMode dataChangeMode) : base(grid, dataItem, dataChangeMode)
+        internal GridDataItemChangingEventArgs(TiamGrid<TDataItem> grid, TDataItem dataItem, TrackingState trackingState) : base(grid, dataItem, trackingState)
         {
         }
 
@@ -26,16 +26,16 @@ namespace TIAMSharedUI.Shared.Components.Grids
 
     public class GridDataItemChangedEventArgs<TDataItem> where TDataItem : class, IId<Guid>
     {
-        internal GridDataItemChangedEventArgs(TiamGrid<TDataItem> grid, TDataItem dataItem, DataChangeMode dataChangeMode)
+        internal GridDataItemChangedEventArgs(TiamGrid<TDataItem> grid, TDataItem dataItem, TrackingState trackingState)
         {
             Grid = grid;
             DataItem = dataItem;
-            DataChangeMode = dataChangeMode;
+            TrackingState = trackingState;
         }
 
         public TiamGrid<TDataItem> Grid { get; }
         public TDataItem DataItem { get; }
-        public DataChangeMode DataChangeMode { get; }
+        public TrackingState TrackingState { get; }
     }
 
     public class TiamGrid<TDataItem> : DxGrid where TDataItem : class, IId<Guid>
@@ -121,13 +121,13 @@ namespace TIAMSharedUI.Shared.Components.Grids
         }
 
         public Task AddDataItem(TDataItem dataItem) => AddDataItem(dataItem, AddMessageTag);
-        public Task AddDataItem(TDataItem dataItem, int messageTag) => PostDataToServerAsync(dataItem, messageTag, DataChangeMode.Add);
+        public Task AddDataItem(TDataItem dataItem, int messageTag) => PostDataToServerAsync(dataItem, messageTag, TrackingState.Add);
 
         public Task UpdateDataItem(TDataItem dataItem) => UpdateDataItem(dataItem, UpdateMessageTag);
-        public Task UpdateDataItem(TDataItem dataItem, int messageTag) => PostDataToServerAsync(dataItem, messageTag, DataChangeMode.Update);
+        public Task UpdateDataItem(TDataItem dataItem, int messageTag) => PostDataToServerAsync(dataItem, messageTag, TrackingState.Update);
 
         public Task RemoveDataItem(TDataItem dataItem) => RemoveDataItem(dataItem, RemoveMessageTag);
-        public Task RemoveDataItem(TDataItem dataItem, int messageTag) => PostDataToServerAsync(dataItem, messageTag, DataChangeMode.Remove);
+        public Task RemoveDataItem(TDataItem dataItem, int messageTag) => PostDataToServerAsync(dataItem, messageTag, TrackingState.Remove);
 
         public Task RemoveDataItem(Guid id) => RemoveDataItem(id, RemoveMessageTag);
 
@@ -192,9 +192,9 @@ namespace TIAMSharedUI.Shared.Components.Grids
             });
         }
 
-        protected virtual async Task PostDataToServerAsync(TDataItem dataItem, int messageTag, DataChangeMode dataChangeMode)
+        protected virtual async Task PostDataToServerAsync(TDataItem dataItem, int messageTag, TrackingState trackingState)
         {
-            var changingEventArgs = new GridDataItemChangingEventArgs<TDataItem>(this, dataItem, dataChangeMode);
+            var changingEventArgs = new GridDataItemChangingEventArgs<TDataItem>(this, dataItem, trackingState);
             await OnDataItemChanging.InvokeAsync(changingEventArgs);
 
             if (changingEventArgs.IsCanceled)
@@ -209,7 +209,7 @@ namespace TIAMSharedUI.Shared.Components.Grids
 
             if (dataItem.Id.IsNullOrEmpty()) dataItem.Id = Guid.NewGuid();
 
-            _dataSource.UpdateCollection(dataItem, dataChangeMode == DataChangeMode.Remove); //egyből látszódik a változás a grid-ben, nem csak a callback lefutásakor! felhasználóbarátabb... - J.
+            _dataSource.UpdateCollection(dataItem, trackingState == TrackingState.Remove); //egyből látszódik a változás a grid-ben, nem csak a callback lefutásakor! felhasználóbarátabb... - J.
 
             SignalRClient.PostDataAsync(messageTag, dataItem, async response =>
             {
@@ -219,9 +219,9 @@ namespace TIAMSharedUI.Shared.Components.Grids
                     return;
                 }
 
-                _dataSource.UpdateCollection(response.ResponseData, dataChangeMode == DataChangeMode.Remove);
+                _dataSource.UpdateCollection(response.ResponseData, trackingState == TrackingState.Remove);
 
-                var changedEventArgs = new GridDataItemChangedEventArgs<TDataItem>(this, response.ResponseData, dataChangeMode);
+                var changedEventArgs = new GridDataItemChangedEventArgs<TDataItem>(this, response.ResponseData, trackingState);
                 await OnDataItemChanged.InvokeAsync(changedEventArgs);
 
                 InvokeAsync(StateHasChanged).Forget();
diff --git a/TIAMWebApp/Server/Controllers/ServiceProviderAPIController.cs b/TIAMWebApp/Server/Controllers/ServiceProviderAPIController.cs
index bc7ee8b3..f1f8419d 100644
--- a/TIAMWebApp/Server/Controllers/ServiceProviderAPIController.cs
+++ b/TIAMWebApp/Server/Controllers/ServiceProviderAPIController.cs
@@ -30,9 +30,9 @@ namespace TIAMWebApp.Server.Controllers
 
         [NonAction]
         [ApiExplorerSettings(IgnoreApi = true)]
-        private async Task<bool> CompanyDataChanging(Company company, DataChangeMode dataChangeMode)
+        private async Task<bool> CompanyDataChanging(Company company, TrackingState trackingState)
         {
-            var logText = $"[{dataChangeMode.ToString().ToUpper()}] CompanyDataChanging called; Id: {company.Id}; OwnerId: {company.OwnerId}; Name: {company.Name}";
+            var logText = $"[{trackingState.ToString().ToUpper()}] CompanyDataChanging called; Id: {company.Id}; OwnerId: {company.OwnerId}; Name: {company.Name}";
 
             if (company.Name.IsNullOrEmpty())
             {
@@ -42,9 +42,9 @@ namespace TIAMWebApp.Server.Controllers
 
             _logger.Info(logText);
 
-            switch (dataChangeMode)
+            switch (trackingState)
             {
-                case DataChangeMode.Add:
+                case TrackingState.Add:
                     if (company.Id.IsNullOrEmpty()) company.Id = Guid.NewGuid();
 
                     //if (company.OwnerId.IsNullOrEmpty()) company.OwnerId = Guid.Parse("540271F6-C604-4C16-8160-D5A7CAFEDF00"); //TESZT - J.
@@ -54,13 +54,13 @@ namespace TIAMWebApp.Server.Controllers
 
                     return await adminDal.CreateServiceProviderAsync(company);
 
-                case DataChangeMode.Update:
+                case TrackingState.Update:
                     return await adminDal.UpdateCompanyAsync(company);
-                case DataChangeMode.Remove:
+                case TrackingState.Remove:
                     return await adminDal.RemoveCompanyAsync(company);
 
                 default:
-                    throw new ArgumentOutOfRangeException(nameof(dataChangeMode), dataChangeMode, null);
+                    throw new ArgumentOutOfRangeException(nameof(trackingState), trackingState, null);
             }
         }
         
@@ -68,21 +68,21 @@ namespace TIAMWebApp.Server.Controllers
         [ApiExplorerSettings(IgnoreApi = true)]
         [SignalR(SignalRTags.AddCompany)]
         public async Task<string> AddCompanyAsync(Company company)
-            => await CompanyDataChanging(company, DataChangeMode.Add) ? company.ToJson() : string.Empty;
+            => await CompanyDataChanging(company, TrackingState.Add) ? company.ToJson() : string.Empty;
 
         [AllowAnonymous]
         [HttpPost]
         [Route(APIUrls.UpdateServiceProviderRouteName)]
         [SignalR(SignalRTags.UpdateCompany)]
         public async Task<string> UpdateServiceProvider(Company company)
-            => await CompanyDataChanging(company, DataChangeMode.Update) ? company.ToJson() : string.Empty;
+            => await CompanyDataChanging(company, TrackingState.Update) ? company.ToJson() : string.Empty;
 
         [AllowAnonymous]
         [HttpPost]
         [Route(APIUrls.RemoveServiceProviderRouteName)]
         [SignalR(SignalRTags.RemoveCompany)]
         public async Task<string> RemoveServiceProvider(Company company)
-            => await CompanyDataChanging(company, DataChangeMode.Remove) ? company.ToJson() : string.Empty;
+            => await CompanyDataChanging(company, TrackingState.Remove) ? company.ToJson() : string.Empty;
 
         //15.
         [AllowAnonymous]
@@ -220,9 +220,9 @@ namespace TIAMWebApp.Server.Controllers
 
         [NonAction]
         [ApiExplorerSettings(IgnoreApi = true)]
-        private async Task<bool> CarDataChanging(Car car, DataChangeMode dataChangeMode)
+        private async Task<bool> CarDataChanging(Car car, TrackingState trackingState)
         {
-            var logText = $"[{dataChangeMode.ToString().ToUpper()}] CarDataChanging called; Id: {car.Id}; OwnerId: {car.UserProductMappingId}; LicensePlate: {car.LicencePlate}";
+            var logText = $"[{trackingState.ToString().ToUpper()}] CarDataChanging called; Id: {car.Id}; OwnerId: {car.UserProductMappingId}; LicensePlate: {car.LicencePlate}";
 
             if (car.UserProductMappingId.IsNullOrEmpty() || car.LicencePlate.IsNullOrWhiteSpace())
             {
@@ -232,19 +232,19 @@ namespace TIAMWebApp.Server.Controllers
 
             _logger.Info(logText);
 
-            switch (dataChangeMode)
+            switch (trackingState)
             {
-                case DataChangeMode.Add:
+                case TrackingState.Add:
                     if (car.Id.IsNullOrEmpty()) car.Id = Guid.NewGuid();
 
                     return await adminDal.AddCarAsync(car);
-                case DataChangeMode.Update:
+                case TrackingState.Update:
                     return await adminDal.UpdateCarAsync(car);
-                case DataChangeMode.Remove:
+                case TrackingState.Remove:
                     return await adminDal.RemoveCarAsync(car);
 
                 default:
-                    throw new ArgumentOutOfRangeException(nameof(dataChangeMode), dataChangeMode, null);
+                    throw new ArgumentOutOfRangeException(nameof(trackingState), trackingState, null);
             }
         }
 
@@ -255,7 +255,7 @@ namespace TIAMWebApp.Server.Controllers
         [EndpointSummary("Create car")]
         [SignalR(SignalRTags.CreateCar)]
         public async Task<IActionResult> CreateCar(Car car)
-            => await CarDataChanging(car, DataChangeMode.Add) ? Ok(car) : BadRequest("Invalid request");
+            => await CarDataChanging(car, TrackingState.Add) ? Ok(car) : BadRequest("Invalid request");
 
         [AllowAnonymous]
         [HttpPost]
@@ -264,7 +264,7 @@ namespace TIAMWebApp.Server.Controllers
         [EndpointSummary("Update car")]
         [SignalR(SignalRTags.UpdateCar)]
         public async Task<IActionResult> UpdateCar(Car car)
-            => await CarDataChanging(car, DataChangeMode.Update) ? Ok(car) : BadRequest("Invalid request");
+            => await CarDataChanging(car, TrackingState.Update) ? Ok(car) : BadRequest("Invalid request");
 
         [AllowAnonymous]
         [HttpPost]
@@ -273,7 +273,7 @@ namespace TIAMWebApp.Server.Controllers
         [EndpointSummary("Delete car")]
         [SignalR(SignalRTags.DeleteCar)]
         public async Task<IActionResult> DeleteCar(Car car)
-            => await CarDataChanging(car, DataChangeMode.Remove) ? Ok(car) : BadRequest("Invalid request");
+            => await CarDataChanging(car, TrackingState.Remove) ? Ok(car) : BadRequest("Invalid request");
 
         [HttpPost]
         [Route(APIUrls.AddProductRouteName)]
diff --git a/TIAMWebApp/Shared/Services/AcSignalRClientBase.cs b/TIAMWebApp/Shared/Services/AcSignalRClientBase.cs
index b9200d75..d531c604 100644
--- a/TIAMWebApp/Shared/Services/AcSignalRClientBase.cs
+++ b/TIAMWebApp/Shared/Services/AcSignalRClientBase.cs
@@ -2,6 +2,7 @@
 using AyCode.Core;
 using AyCode.Core.Extensions;
 using AyCode.Core.Helpers;
+using AyCode.Core.Interfaces;
 using AyCode.Services.Loggers;
 using AyCode.Services.SignalRs;
 using MessagePack.Resolvers;
@@ -75,9 +76,6 @@ namespace TIAMWebApp.Shared.Application.Services
         public virtual Task SendMessageToServerAsync(int messageTag)
             => SendMessageToServerAsync(messageTag, null, AcDomain.NextUniqueInt32);
 
-        public virtual Task SendMessageToServerAsync(int messageTag, int requestId)
-            => SendMessageToServerAsync(messageTag, null, requestId);
-
         public virtual async Task SendMessageToServerAsync(int messageTag, ISignalRMessage? message, int? requestId)
         {
             Logger.DebugConditional($"Client SendMessageToServerAsync; {nameof(messageTag)}: {messageTag}; {nameof(requestId)}: {requestId};");
@@ -89,8 +87,8 @@ namespace TIAMWebApp.Shared.Application.Services
         }
 
         #region CRUD
-        public virtual Task<TResponse?> GetByIdAsync<TResponse>(int messageTag, Guid id) where TResponse : class
-            => SendMessageToServerAsync<TResponse>(messageTag, new SignalPostJsonDataMessage<IdMessage>(new IdMessage(id)), AcDomain.NextUniqueInt32);
+        public virtual Task<TResponseData?> GetByIdAsync<TResponseData>(int messageTag, Guid id) where TResponseData : class
+            => SendMessageToServerAsync<TResponseData>(messageTag, new SignalPostJsonDataMessage<IdMessage>(new IdMessage(id)), AcDomain.NextUniqueInt32);
         public virtual Task GetByIdAsync<TResponseData>(int messageTag, Guid id, Action<ISignalResponseMessage<TResponseData?>> responseCallback)
             => SendMessageToServerAsync(messageTag, new SignalPostJsonDataMessage<IdMessage>(new IdMessage(id)), responseCallback);
 
@@ -117,7 +115,7 @@ namespace TIAMWebApp.Shared.Application.Services
         public virtual Task<TResponse?> SendMessageToServerAsync<TResponse>(int messageTag, ISignalRMessage? message) where TResponse : class
             => SendMessageToServerAsync<TResponse>(messageTag, message, AcDomain.NextUniqueInt32);
 
-        public virtual async Task<TResponse?> SendMessageToServerAsync<TResponse>(int messageTag, ISignalRMessage? message, int requestId) where TResponse : class
+        protected virtual async Task<TResponse?> SendMessageToServerAsync<TResponse>(int messageTag, ISignalRMessage? message, int requestId) where TResponse : class
         {
             Logger.DebugConditional($"Client SendMessageToServerAsync<TResult>; {nameof(messageTag)}: {messageTag}; {nameof(requestId)}: {requestId};");
             
diff --git a/TIAMWebApp/Shared/Utility/SignalRDataSource.cs b/TIAMWebApp/Shared/Utility/SignalRDataSource.cs
index 37780551..19b2c826 100644
--- a/TIAMWebApp/Shared/Utility/SignalRDataSource.cs
+++ b/TIAMWebApp/Shared/Utility/SignalRDataSource.cs
@@ -1,6 +1,10 @@
 using System.Collections;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.Serialization;
+using System.Runtime.Serialization.Formatters.Binary;
 using AyCode.Core.Enums;
 using AyCode.Core.Extensions;
 using AyCode.Core.Interfaces;
@@ -10,22 +14,84 @@ using TIAMWebApp.Shared.Application.Services;
 
 namespace TIAMWebApp.Shared.Application.Utility
 {
-    public class ChangeTracking<T>(DataChangeMode dataChangeMode, T newItem, T originalItem = default(T))where T: class, IId<Guid>
+    public class TrackingItem<T>(TrackingState trackingState, T currentValue, T? originalValue = null) where T : class, IId<Guid>
     {
-        public DataChangeMode DataChangeMode { get; init; } = dataChangeMode;
-        public T NewItem { get; init; } = newItem;
-        public T OriginalItem { get; init; } = originalItem;
+        public TrackingState TrackingState { get; internal set; } = trackingState;
+        public T CurrentValue { get; internal set; } = currentValue;
+        public T? OriginalValue { get; init; } = originalValue; //originalValue == null ? null : TrackingItemHelpers.Clone(originalValue);
+
+        internal TrackingItem<T> UpdateItem(TrackingState trackingState, T newValue)
+        {
+            CurrentValue = newValue;
+
+            if (TrackingState != TrackingState.Add)
+                TrackingState = trackingState;
+
+            return this;
+        }
     }
 
+
+    public class ChangeTracking<T> where T : class, IId<Guid>
+    {
+        private readonly List<TrackingItem<T>> _trackingItems = []; //TODO: Dictionary... - J.
+
+        internal TrackingItem<T>? AddTrackingItem(TrackingState trackingState, T newValue, T? originalValue = null)
+        {
+            if (newValue.Id.IsNullOrEmpty()) throw new ArgumentNullException(nameof(newValue), $@"currentValue.Id.IsNullOrEmpty()");
+
+            var itemIndex = _trackingItems.FindIndex(x => x.CurrentValue.Id == newValue.Id);
+            TrackingItem<T>? trackingItem = null;
+
+            if (itemIndex > -1)
+            {
+                trackingItem = _trackingItems[itemIndex];
+
+                if (trackingState == TrackingState.Remove && trackingItem.TrackingState == TrackingState.Add)
+                {
+                    _trackingItems.RemoveAt(itemIndex);
+                    return null;
+                }
+
+                return trackingItem.UpdateItem(trackingState, newValue);
+
+            }
+
+            if (originalValue != null && Equals(newValue, originalValue))
+                originalValue = TrackingItemHelpers.ReflectionClone(originalValue);
+
+            trackingItem = new TrackingItem<T>(trackingState, newValue, originalValue);
+            _trackingItems.Add(trackingItem);
+
+            return trackingItem;
+        }
+
+        public int Count => _trackingItems.Count;
+        internal void Clear() => _trackingItems.Clear();
+        public List<TrackingItem<T>> ToList() => _trackingItems.ToList();
+
+        public bool TryGetTrackingItem(Guid id, [NotNullWhen(true)] out TrackingItem<T>? trackingItem)
+        {
+            trackingItem = _trackingItems.FirstOrDefault(x => x.CurrentValue.Id == id);
+            return trackingItem != null;
+        }
+
+        internal void Remove(TrackingItem<T> trackingItem) => _trackingItems.Remove(trackingItem);
+    }
+
+
+
     [Serializable]
     [DebuggerDisplay("Count = {Count}")]
-    public class SignalRDataSource<T> : IList<T>, IList, IReadOnlyList<T> where T: class, IId<Guid>
+    public class SignalRDataSource<T> : IList<T>, IList, IReadOnlyList<T> where T : class, IId<Guid>
     {
-        protected readonly List<T> InnerList = [];
         private readonly object _syncRoot = new();
 
-        protected Guid? ContextId;
-        protected AcSignalRClientBase SignalRClient;
+        protected readonly List<T> InnerList = []; //TODO: Dictionary??? - J.
+        protected readonly ChangeTracking<T> TrackingItems = new();
+
+        protected readonly Guid? ContextId;
+        protected readonly AcSignalRClientBase SignalRClient;
         protected readonly SignalRCrudTags SignalRCrudTags;
 
         public SignalRDataSource(AcSignalRClientBase signalRClient, SignalRCrudTags signalRCrudTags, Guid? contextId = null, bool autoLoadDataSource = true)
@@ -35,7 +101,7 @@ namespace TIAMWebApp.Shared.Application.Utility
             SignalRCrudTags = signalRCrudTags;
             SignalRClient = signalRClient;
 
-            if (autoLoadDataSource) LoadDataSource();
+            if (autoLoadDataSource) LoadDataSource(false);
         }
 
         public bool IsSynchronized => true;
@@ -47,19 +113,38 @@ namespace TIAMWebApp.Shared.Application.Utility
         /// </summary>
         /// <exception cref="ArgumentException"></exception>
         /// <exception cref="NullReferenceException"></exception>
-        public void LoadDataSource()
+        public void LoadDataSource(bool clearChangeTracking = true)
         {
-            if (SignalRCrudTags.GetAllMessageTag == SignalRTags.None) throw new ArgumentException($"_signalRCrudTags.GetAllMessageTag == SignalRTags.None;");
+            if (SignalRCrudTags.GetAllMessageTag == SignalRTags.None) throw new ArgumentException($"SignalRCrudTags.GetAllMessageTag == SignalRTags.None");
 
             lock (_syncRoot)
             {
                 var resultList = SignalRClient.GetAllAsync<List<T>>(SignalRCrudTags.GetAllMessageTag, ContextId).GetAwaiter().GetResult() ?? throw new NullReferenceException();
 
-                Clear();
+                Clear(clearChangeTracking);
                 InnerList.AddRange(resultList);
             }
         }
 
+        public T? LoadItem(Guid id)
+        {
+            if (SignalRCrudTags.GetItemMessageTag == SignalRTags.None) throw new ArgumentException($"SignalRCrudTags.GetItemMessageTag == SignalRTags.None");
+
+            T? resultitem = null;
+
+            lock (_syncRoot)
+            {
+                resultitem = SignalRClient.GetByIdAsync<T>(SignalRCrudTags.GetItemMessageTag, id).GetAwaiter().GetResult();
+                if (resultitem == null) return null;
+
+                if (TryGetIndex(id, out var index)) InnerList[index] = resultitem;
+                else InnerList.Add(resultitem);
+            }
+
+            return resultitem;
+        }
+
+
         /// <summary>
         /// set: UpdateMessageTag
         /// </summary>
@@ -86,42 +171,38 @@ namespace TIAMWebApp.Shared.Application.Utility
             }
         }
 
-        public int Count
-        {
-            get
-            {
-                lock (_syncRoot) return InnerList.Count;
-            }
-        }
-
         /// <summary>
         /// AddMessageTag
         /// </summary>
-        /// <param name="item"></param>
+        /// <param name="newValue"></param>
         /// <exception cref="ArgumentException"></exception>
-        public void Add(T item)
+        public void Add(T newValue)
         {
+            if (newValue.Id.IsNullOrEmpty()) throw new ArgumentNullException(nameof(newValue), @"Add->newValue.Id.IsNullOrEmpty()");
+
             lock (_syncRoot)
             {
-                if (Contains(item))
-                    throw new ArgumentException($@"It already contains this Id! Id: {item.Id}", nameof(item));
+                if (Contains(newValue))
+                    throw new ArgumentException($@"It already contains this Id! Id: {newValue.Id}", nameof(newValue));
 
-                UnsafeAdd(item);
+                UnsafeAdd(newValue);
             }
         }
 
         /// <summary>
         /// AddMessageTag or UpdateMessageTag
         /// </summary>
-        /// <param name="item"></param>
+        /// <param name="newValue"></param>
         /// <returns></returns>
-        public T AddOrUpdate(T item)
+        public T AddOrUpdate(T newValue)
         {
+            if (newValue.Id.IsNullOrEmpty()) throw new ArgumentNullException(nameof(newValue), @"AddOrUpdate->newValue.Id.IsNullOrEmpty()");
+
             lock (_syncRoot)
             {
-                var index = IndexOf(item);
+                var index = IndexOf(newValue);
 
-                return index > -1 ? Update(index, item) : UnsafeAdd(item);
+                return index > -1 ? Update(index, newValue) : UnsafeAdd(newValue);
             }
         }
 
@@ -133,69 +214,67 @@ namespace TIAMWebApp.Shared.Application.Utility
         //    }
         //}
 
-        private T UnsafeAdd(T item)
+        protected T UnsafeAdd(T newValue)
         {
-            if (SignalRCrudTags.AddMessageTag == SignalRTags.None) throw new ArgumentException($"_signalRCrudTags.AddMessageTag == SignalRTags.None;");
+            TrackingItems.AddTrackingItem(TrackingState.Add, newValue);
+            InnerList.Add(newValue);
 
-            var result = SignalRClient.PostDataAsync(SignalRCrudTags.AddMessageTag, item).GetAwaiter().GetResult() ?? throw new NullReferenceException();
-            InnerList.Add(result);
-
-            return result;
+            return newValue;
         }
 
         /// <summary>
         /// AddMessageTag
         /// </summary>
         /// <param name="index"></param>
-        /// <param name="item"></param>
+        /// <param name="newValue"></param>
         /// <exception cref="ArgumentException"></exception>
         /// <exception cref="NullReferenceException"></exception>
-        public void Insert(int index, T item)
+        public void Insert(int index, T newValue)
         {
-            if (SignalRCrudTags.AddMessageTag == SignalRTags.None) throw new ArgumentException($"_signalRCrudTags.AddMessageTag == SignalRTags.None;");
+            if (newValue.Id.IsNullOrEmpty()) throw new ArgumentNullException(nameof(newValue), @"Insert->newValue.Id.IsNullOrEmpty()");
 
             lock (_syncRoot)
             {
-                if (Contains(item))
-                    throw new ArgumentException($@"It already contains this Id! Id: {item.Id}", nameof(item));
+                if (Contains(newValue))
+                    throw new ArgumentException($@"It already contains this Id! Id: {newValue.Id}", nameof(newValue));
 
-                var result = SignalRClient.PostDataAsync(SignalRCrudTags.AddMessageTag, item).GetAwaiter().GetResult() ?? throw new NullReferenceException();
-                InnerList.Insert(index, result);
+                TrackingItems.AddTrackingItem(TrackingState.Add, newValue);
+                InnerList.Insert(index, newValue);
             }
         }
 
         /// <summary>
         /// UpdateMessageTag
         /// </summary>
-        /// <param name="item"></param>
-        public T Update(T item) => Update(IndexOf(item), item);
+        /// <param name="newItem"></param>
+        public T Update(T newItem) => Update(IndexOf(newItem), newItem);
 
         /// <summary>
         /// UpdateMessageTag
         /// </summary>
         /// <param name="index"></param>
-        /// <param name="item"></param>
+        /// <param name="newValue"></param>
         /// /// <exception cref="ArgumentException"></exception>
         /// /// <exception cref="NullReferenceException"></exception>
         /// <exception cref="ArgumentNullException"></exception>
         /// <exception cref="ArgumentOutOfRangeException"></exception>
-        public T Update(int index, T item)
+        public T Update(int index, T newValue)
         {
-            if (SignalRCrudTags.UpdateMessageTag == SignalRTags.None) throw new ArgumentException($"_signalRCrudTags.UpdateMessageTag == SignalRTags.None;");
-
-            if (default(T) != null && item == null) throw new NullReferenceException(nameof(item));
-            if (item.Id.IsNullOrEmpty()) throw new ArgumentNullException(nameof(item), "Update->item.Id.IsNullOrEmpty()");
+            if (default(T) != null && newValue == null) throw new NullReferenceException(nameof(newValue));
+            if (newValue.Id.IsNullOrEmpty()) throw new ArgumentNullException(nameof(newValue), @"Update->newValue.Id.IsNullOrEmpty()");
             if ((uint)index >= (uint)Count) throw new ArgumentOutOfRangeException(nameof(index));
 
             lock (_syncRoot)
             {
-                if (InnerList[index].Id != item.Id)
-                    throw new ArgumentException($@"_list[index].Id != item.Id! Id: {item.Id}", nameof(item));
+                var currentItem = InnerList[index];
 
-                var result = SignalRClient.PostDataAsync(SignalRCrudTags.UpdateMessageTag, item).GetAwaiter().GetResult() ?? throw new NullReferenceException();
-                
-                InnerList[index] = result;
-                return result;
+                if (currentItem.Id != newValue.Id)
+                    throw new ArgumentException($@"currentItem.Id != item.Id! Id: {newValue.Id}", nameof(newValue));
+
+                TrackingItems.AddTrackingItem(TrackingState.Update, newValue, currentItem);
+                InnerList[index] = newValue;
+
+                return newValue;
             }
         }
 
@@ -217,6 +296,20 @@ namespace TIAMWebApp.Shared.Application.Utility
             }
         }
 
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="id"></param>
+        /// <param name="item"></param>
+        /// <returns></returns>
+        public bool TryRemove(Guid id, out T? item)
+        {
+            lock (_syncRoot)
+            {
+                return TryGetValue(id, out item) && Remove(item);
+            }
+        }
+
         /// <summary>
         /// RemoveMessageTag
         /// </summary>
@@ -226,34 +319,197 @@ namespace TIAMWebApp.Shared.Application.Utility
         /// <exception cref="NullReferenceException"></exception>
         public void RemoveAt(int index)
         {
-            if (SignalRCrudTags.RemoveMessageTag == SignalRTags.None) throw new ArgumentException($"_signalRCrudTags.RemoveMessageTag == SignalRTags.None;");
-
             lock (_syncRoot)
             {
-                var item = InnerList[index];
-                if (item.Id.IsNullOrEmpty()) throw new ArgumentNullException(nameof(item), $@"RemoveAt->item.Id.IsNullOrEmpty(); index: {index}");
-
-                var result = SignalRClient.PostDataAsync(SignalRCrudTags.RemoveMessageTag, item).GetAwaiter().GetResult() ?? throw new NullReferenceException();
+                var currentItem = InnerList[index];
+                if (currentItem.Id.IsNullOrEmpty()) throw new ArgumentNullException(nameof(currentItem), $@"RemoveAt->item.Id.IsNullOrEmpty(); index: {index}");
 
+                TrackingItems.AddTrackingItem(TrackingState.Remove, currentItem, currentItem);
                 InnerList.RemoveAt(index);
             }
         }
 
-        public void Clear()
-        {
-            lock (_syncRoot) InnerList.Clear();
-        }
-
-        public int IndexOf(T item)
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <returns></returns>
+        public List<TrackingItem<T>> GetTrackingItems()
         {
             lock (_syncRoot)
-                return InnerList.FindIndex(x => x.Id == item.Id);
+                return TrackingItems.ToList();
         }
 
-        public bool Contains(T item)
+        public void SetTrackingStateToUpdate(T item)
         {
-            lock (_syncRoot) 
-                return IndexOf(item) > -1;
+            if (TrackingItems.TryGetTrackingItem(item.Id, out var trackingItem))
+            {
+                if (trackingItem.TrackingState != TrackingState.Add)
+                    trackingItem.TrackingState = TrackingState.Update;
+
+                return;
+            }
+
+            TrackingItems.AddTrackingItem(TrackingState.Update, item, item);
+        }
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="id"></param>
+        /// <param name="trackingItem"></param>
+        /// <returns></returns>
+        public bool TryGetTrackingItem(Guid id, [NotNullWhen(true)] out TrackingItem<T>? trackingItem)
+        {
+            lock (_syncRoot)
+                return TrackingItems.TryGetTrackingItem(id, out trackingItem);
+        }
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <returns>Unsaved items</returns>
+        public bool SaveChanges(out List<TrackingItem<T>> unsavedItems)
+        {
+            lock (_syncRoot)
+            {
+                foreach (var trackingItem in TrackingItems.ToList())
+                {
+                    try
+                    {
+                        SaveTrackingItemUnsafe(trackingItem);
+                    }
+                    catch
+                    {
+                        // ignored
+                    }
+                }
+
+                unsavedItems = TrackingItems.ToList();
+                return unsavedItems.Count == 0;
+            }
+        }
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="id"></param>
+        /// <param name="resultItem"></param>
+        /// <returns></returns>
+        public bool TrySaveItem(Guid id, [NotNullWhen(true)] out T? resultItem)
+        {
+            resultItem = null;
+
+            if (TryGetTrackingItem(id, out var trackingItem))
+                resultItem = SaveTrackingItemUnsafe(trackingItem);
+
+            return resultItem != null;
+        }
+
+        public bool TrySaveItem(Guid id, TrackingState trackingState, [NotNullWhen(true)] out T? resultItem)
+            => TryGetValue(id, out resultItem) && TrySaveItem(resultItem, trackingState, out resultItem);
+
+        public bool TrySaveItem(T item, TrackingState trackingState, [NotNullWhen(true)] out T? resultItem)
+        {
+            resultItem = SaveItemUnsafe(item, trackingState);
+            return resultItem != null;
+        }
+
+        protected T? SaveTrackingItemUnsafe(TrackingItem<T> trackingItem)
+            => SaveItemUnsafe(trackingItem.CurrentValue, trackingItem.TrackingState);
+
+        protected T? SaveItemUnsafe(T item, TrackingState trackingState)
+        {
+            var messageTag = SignalRCrudTags.GetMessageTagByTrackingState(trackingState);
+            if (messageTag == SignalRTags.None) return null; //throw new ArgumentException($"messageTag == SignalRTags.None");
+
+            var result = SignalRClient.PostDataAsync(messageTag, item).GetAwaiter().GetResult();
+            if (result == null) return null; //throw new NullReferenceException($"result == null");
+
+            if (TryGetTrackingItem(item.Id, out var trackingItem))
+                TrackingItems.Remove(trackingItem);
+
+            if (TryGetIndex(result.Id, out var index))
+                InnerList[index] = result;
+
+            return result;
+        }
+
+        protected void RollbackItemUnsafe(TrackingItem<T> trackingItem)
+        {
+            if (TryGetIndex(trackingItem.CurrentValue.Id, out var index))
+            {
+                if (trackingItem.TrackingState == TrackingState.Add) InnerList.RemoveAt(index);
+                else InnerList[index] = trackingItem.OriginalValue!;
+            }
+            else if (trackingItem.TrackingState != TrackingState.Add)
+                InnerList.Add(trackingItem.OriginalValue!);
+
+            TrackingItems.Remove(trackingItem);
+        }
+
+        public bool TryRollbackItem(Guid id, out T? originalValue)
+        {
+            lock (_syncRoot)
+            {
+                if (TryGetTrackingItem(id, out var trackingItem))
+                {
+                    originalValue = trackingItem.OriginalValue;
+
+                    RollbackItemUnsafe(trackingItem);
+                    return true;
+                }
+
+                originalValue = null;
+                return false;
+            }
+        }
+
+        public void Rollback()
+        {
+            lock (_syncRoot)
+            {
+                foreach (var trackingItem in TrackingItems.ToList())
+                    RollbackItemUnsafe(trackingItem);
+            }
+        }
+
+        public int Count
+        {
+            get
+            {
+                lock (_syncRoot) return InnerList.Count;
+            }
+        }
+
+        public void Clear() => Clear(true);
+
+        public void Clear(bool clearChangeTracking)
+        {
+            lock (_syncRoot)
+            {
+                if (clearChangeTracking) TrackingItems.Clear();
+                InnerList.Clear();
+            }
+        }
+
+        public int IndexOf(Guid id)
+        {
+            lock (_syncRoot)
+                return InnerList.FindIndex(x => x.Id == id);
+        }
+
+        public int IndexOf(T item) => IndexOf(item.Id);
+        public bool TryGetIndex(Guid id, out int index) => (index = IndexOf(id)) > -1;
+
+        public bool Contains(T item) => IndexOf(item) > -1;
+
+        public bool TryGetValue(Guid id, [NotNullWhen(true)] out T? item)
+        {
+            lock (_syncRoot)
+            {
+                item = InnerList.FirstOrDefault(x => x.Id == id);
+                return item != null;
+            }
         }
 
         public void CopyTo(T[] array) => CopyTo(array, 0);
@@ -290,6 +546,7 @@ namespace TIAMWebApp.Shared.Application.Utility
 
 
         #region IList, ICollection
+
         bool IList.IsReadOnly => false;
 
         object? IList.this[int index]
@@ -326,11 +583,11 @@ namespace TIAMWebApp.Shared.Application.Utility
             return Count - 1;
         }
 
-        void IList.Clear() => Clear();
+        void IList.Clear() => Clear(true);
         IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
         bool IList.Contains(object? item) => IsCompatibleObject(item) && Contains((T)item!);
         int IList.IndexOf(object? item) => (IsCompatibleObject(item)) ? IndexOf((T)item!) : -1;
-        
+
         void IList.Insert(int index, object? item)
         {
             if (default(T) != null && item == null) throw new NullReferenceException(nameof(item));
@@ -350,7 +607,7 @@ namespace TIAMWebApp.Shared.Application.Utility
             if (IsCompatibleObject(item)) Remove((T)item!);
         }
 
-        void ICollection<T>.Clear() => Clear();
+        void ICollection<T>.Clear() => Clear(true);
 
         void ICollection.CopyTo(Array array, int arrayIndex)
         {
@@ -361,8 +618,11 @@ namespace TIAMWebApp.Shared.Application.Utility
 
             try
             {
-                //TODO: _list.ToArray() - ez nem az igazi... - J.
-                Array.Copy(InnerList.ToArray(), 0, array!, arrayIndex, InnerList.Count);
+                lock (_syncRoot)
+                {
+                    //TODO: _list.ToArray() - ez nem az igazi... - J.
+                    Array.Copy(InnerList.ToArray(), 0, array!, arrayIndex, InnerList.Count);
+                }
             }
             catch (ArrayTypeMismatchException)
             {
@@ -375,6 +635,7 @@ namespace TIAMWebApp.Shared.Application.Utility
         bool ICollection<T>.IsReadOnly => false;
         void IList<T>.RemoveAt(int index) => RemoveAt(index);
         int IReadOnlyCollection<T>.Count => Count;
+
         #endregion IList, ICollection
     }
 }
diff --git a/TIAMWebApp/Shared/Utility/SignalRDataSourceAsync.cs b/TIAMWebApp/Shared/Utility/SignalRDataSourceAsync.cs
index f46ff930..e6361fa2 100644
--- a/TIAMWebApp/Shared/Utility/SignalRDataSourceAsync.cs
+++ b/TIAMWebApp/Shared/Utility/SignalRDataSourceAsync.cs
@@ -23,7 +23,7 @@ public class SignalRDataSourceAsync<T> : SignalRDataSource<T> where T : class, I
         if (autoLoadDataSource) LoadDataSourceAsync();
     }
 
-    public void LoadDataSourceAsync()
+    public void LoadDataSourceAsync(bool clearChangeTracking = true)
     {
         if (SignalRCrudTags.GetAllMessageTag == SignalRTags.None) throw new ArgumentException($"_signalRCrudTags.GetAllMessageTag == SignalRTags.None;");
         
@@ -39,7 +39,7 @@ public class SignalRDataSourceAsync<T> : SignalRDataSource<T> where T : class, I
                     if (response.Status == SignalResponseStatus.Error) throw new Exception($"LoadDataSourceAsync; response.Status == SignalResponseStatus.Error");
                     if (response.ResponseData == null) throw new NullReferenceException($"response.ResponseData == null");
 
-                    Clear();
+                    Clear(clearChangeTracking);
                     InnerList.AddRange(response.ResponseData);
                 }
                 finally
@@ -58,13 +58,13 @@ public class SignalRDataSourceAsync<T> : SignalRDataSource<T> where T : class, I
     }
 
 
-    //public T Add(T item, int messageTag) => PostDataToServerAsync(item, messageTag, DataChangeMode.Add).GetAwaiter().GetResult();
-    //public Task AddAsync(T item, int messageTag) => PostDataToServerAsync(item, messageTag, DataChangeMode.Add);
+    //public T Add(T item, int messageTag) => PostDataToServerAsync(item, messageTag, TrackingState.Add).GetAwaiter().GetResult();
+    //public Task AddAsync(T item, int messageTag) => PostDataToServerAsync(item, messageTag, TrackingState.Add);
         
 
-    //public Task UpdateAsync(T item, int messageTag) => PostDataToServerAsync(item, messageTag, DataChangeMode.Update);
+    //public Task UpdateAsync(T item, int messageTag) => PostDataToServerAsync(item, messageTag, TrackingState.Update);
 
-    //public Task RemoveAsync(T item, int messageTag) => PostDataToServerAsync(item, messageTag, DataChangeMode.Remove);
+    //public Task RemoveAsync(T item, int messageTag) => PostDataToServerAsync(item, messageTag, TrackingState.Remove);
 
     //public Task RemoveAsync(Guid id, int messageTag)
     //{
@@ -73,7 +73,7 @@ public class SignalRDataSourceAsync<T> : SignalRDataSource<T> where T : class, I
     //    return item == null ? Task.CompletedTask : RemoveAsync(item, messageTag);
     //}
 
-    //protected virtual Task PostDataToServerAsync(T item, int messageTag, DataChangeMode dataChangeMode)
+    //protected virtual Task PostDataToServerAsync(T item, int messageTag, TrackingState trackingState)
     //{
     //    if (messageTag == 0) return Task.CompletedTask;
 
@@ -81,7 +81,7 @@ public class SignalRDataSourceAsync<T> : SignalRDataSource<T> where T : class, I
 
     //    if (item.Id.IsNullOrEmpty()) item.Id = Guid.NewGuid();
 
-    //    _list.UpdateCollection(item, dataChangeMode == DataChangeMode.Remove); //egyből látszódik a változás a grid-ben, nem csak a callback lefutásakor! felhasználóbarátabb... - J.
+    //    _list.UpdateCollection(item, trackingState == TrackingState.Remove); //egyből látszódik a változás a grid-ben, nem csak a callback lefutásakor! felhasználóbarátabb... - J.
 
     //    await _signalRClient.PostDataAsync(messageTag, item, async repsonse =>
     //    {
@@ -91,9 +91,9 @@ public class SignalRDataSourceAsync<T> : SignalRDataSource<T> where T : class, I
     //            return;
     //        }
 
-    //        _list.UpdateCollection(repsonse.ResponseData, dataChangeMode == DataChangeMode.Remove);
+    //        _list.UpdateCollection(repsonse.ResponseData, trackingState == TrackingState.Remove);
 
-    //        var eventArgs = new ItemChangedEventArgs<T>(repsonse.ResponseData, dataChangeMode);
+    //        var eventArgs = new ItemChangedEventArgs<T>(repsonse.ResponseData, trackingState);
     //        OnItemChanged.Invoke(eventArgs);
     //    });
 
@@ -104,14 +104,14 @@ public class SignalRDataSourceAsync<T> : SignalRDataSource<T> where T : class, I
 
     public class ItemChangedEventArgs<T> where T : IId<Guid>
     {
-        internal ItemChangedEventArgs(T item, DataChangeMode dataChangeMode)
+        internal ItemChangedEventArgs(T item, TrackingState trackingState)
         {
             Item = item;
-            DataChangeMode = dataChangeMode;
+            TrackingState = trackingState;
         }
 
         public T Item { get; }
-        public DataChangeMode DataChangeMode { get; }
+        public TrackingState TrackingState { get; }
     }
 
 }
\ No newline at end of file
diff --git a/TIAMWebApp/Shared/Utility/TrackingItemHelpers.cs b/TIAMWebApp/Shared/Utility/TrackingItemHelpers.cs
new file mode 100644
index 00000000..34b5eadc
--- /dev/null
+++ b/TIAMWebApp/Shared/Utility/TrackingItemHelpers.cs
@@ -0,0 +1,47 @@
+using System.Reflection;
+using System.Text.Json;
+using AyCode.Core.Extensions;
+
+namespace TIAMWebApp.Shared.Application.Utility;
+
+public static class TrackingItemHelpers
+{
+    public static T JsonClone<T>(T source) => source.ToJson().JsonTo<T>()!;
+
+    public static T ReflectionClone<T>(T source)
+    {
+        var type = source!.GetType();
+
+        if (type.IsPrimitive || typeof(string) == type)
+            return source;
+
+        if (type.IsArray)
+        {
+            var elementType = Type.GetType(type.FullName!.Replace("[]", string.Empty))!;
+            var array = (source as Array)!;
+            var cloned = Array.CreateInstance(elementType, array.Length);
+
+            for (var i = 0; i < array.Length; i++)
+                cloned.SetValue(ReflectionClone(array.GetValue(i)), i);
+
+            return (T)Convert.ChangeType(cloned, type);
+        }
+
+        var clone = Activator.CreateInstance(type);
+
+        while (type != null && type != typeof(object))
+        {
+            foreach (var field in type.GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance))
+            {
+                var fieldValue = field.GetValue(source);
+                if (fieldValue == null) continue;
+
+                field.SetValue(clone, ReflectionClone(fieldValue));
+            }
+
+            type = type.BaseType;
+        }
+
+        return (T)clone!;
+    }
+}
\ No newline at end of file