update

Pilz/Data/IDataObject.cs

@@ -2,5 +2,5 @@
 
 public interface IDataObject
 {
-    public int Id { get; }
+    public int Id { get; set; }
 }

Pilz/Data/Json/JsonDataContainer.cs

@@ -4,21 +4,27 @@ namespace Pilz.Data.Json;
 
 public abstract class JsonDataContainer
 {
+    public class DataSet<T>
+    {
+        public int LastId { get; set; }
+        public HashSet<T> Data { get; } = [];
+    }
+
     [JsonProperty("Sets")]
     protected readonly HashSet<object> sets = [];
 
-    public virtual HashSet<T>? Set<T>(bool allowCreate) where T : class, IDataObject
+    public virtual DataSet<T>? Set<T>(bool allowCreate) where T : class, IDataObject
     {
         lock (sets)
         {
-            var list = sets.OfType<HashSet<T>>().FirstOrDefault();
+            var list = sets.OfType<DataSet<T>>().FirstOrDefault();
 
             if (list == null && allowCreate)
             {
-                list = [];
+                list = new();
                 sets.Add(list);
             }
-
+            
             return list;
         }
     }

Pilz/Data/Json/JsonDataManager.cs

@@ -8,22 +8,24 @@ public class JsonDataManager(JsonDataContainer container) : DataManager
     {
         if (id == 0)
             return null;
-        return container.Set<T>(false)?.FirstOrDefault(n => n.Id == id);
+        return container.Set<T>(false)?.Data.FirstOrDefault(n => n.Id == id);
     }
 
     protected override IQueryable<T> GetEntitySet<T>()
     {
-        return container.Set<T>(true).AsQueryable();
+        return container.Set<T>(true).Data.AsQueryable();
     }
 
     protected override void RemoveEntity<T>(T obj)
     {
-        container.Set<T>(false)?.Remove(obj);
+        container.Set<T>(false)?.Data.Remove(obj);
     }
 
     protected override void UpdateEntity<T>(T obj)
     {
-        container.Set<T>(true).Add(obj);
+        var set = container.Set<T>(true);
+        obj.Id = ++set.LastId;
+        set.Data.Add(obj);
     }
 
     protected override void SaveChanges()

Pilz/Pilz.csproj

@@ -5,7 +5,7 @@
     <LangVersion>latest</LangVersion>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>annotations</Nullable>
-    <Version>2.4.5</Version>
+    <Version>2.4.6</Version>
   </PropertyGroup>
   
   <ItemGroup>