diff --git a/src/Squidex.Domain.Apps.Core.Model/Apps/AppClients.cs b/src/Squidex.Domain.Apps.Core.Model/Apps/AppClients.cs
index 425c14dbf..3646682a7 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Apps/AppClients.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Apps/AppClients.cs
@@ -5,49 +5,60 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
+using System;
+using System.Collections.Generic;
 using System.Diagnostics.Contracts;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 
 namespace Squidex.Domain.Apps.Core.Apps
 {
-    public sealed class AppClients : DictionaryWrapper<string, AppClient>
+    public sealed class AppClients : ArrayDictionary<string, AppClient>
     {
         public static readonly AppClients Empty = new AppClients();
 
         private AppClients()
-            : base(ImmutableDictionary<string, AppClient>.Empty)
         {
         }
 
-        public AppClients(ImmutableDictionary<string, AppClient> inner)
-            : base(inner)
+        public AppClients(KeyValuePair<string, AppClient>[] items)
+            : base(items)
         {
         }
 
         [Pure]
-        public AppClients Add(string id, AppClient client)
+        public AppClients Revoke(string id)
         {
             Guard.NotNullOrEmpty(id, nameof(id));
-            Guard.NotNull(client, nameof(client));
 
-            return new AppClients(Inner.Add(id, client));
+            return new AppClients(Without(id));
         }
 
         [Pure]
-        public AppClients Add(string id, string secret)
+        public AppClients Add(string id, AppClient client)
         {
             Guard.NotNullOrEmpty(id, nameof(id));
+            Guard.NotNull(client, nameof(client));
+
+            if (ContainsKey(id))
+            {
+                throw new ArgumentException("Id already exists.", nameof(id));
+            }
 
-            return new AppClients(Inner.Add(id, new AppClient(id, secret, Role.Editor)));
+            return new AppClients(With(id, client));
         }
 
         [Pure]
-        public AppClients Revoke(string id)
+        public AppClients Add(string id, string secret)
         {
             Guard.NotNullOrEmpty(id, nameof(id));
 
-            return new AppClients(Inner.Remove(id));
+            if (ContainsKey(id))
+            {
+                throw new ArgumentException("Id already exists.", nameof(id));
+            }
+
+            return new AppClients(With(id, new AppClient(id, secret, Role.Editor)));
         }
 
         [Pure]
@@ -60,7 +71,7 @@ namespace Squidex.Domain.Apps.Core.Apps
                 return this;
             }
 
-            return new AppClients(Inner.SetItem(id, client.Rename(newName)));
+            return new AppClients(With(id, client.Rename(newName)));
         }
 
         [Pure]
@@ -73,7 +84,7 @@ namespace Squidex.Domain.Apps.Core.Apps
                 return this;
             }
 
-            return new AppClients(Inner.SetItem(id, client.Update(role)));
+            return new AppClients(With(id, client.Update(role)));
         }
     }
 }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Apps/AppContributors.cs b/src/Squidex.Domain.Apps.Core.Model/Apps/AppContributors.cs
index e3bd81ab4..ee54ae6fb 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Apps/AppContributors.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Apps/AppContributors.cs
@@ -5,23 +5,23 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
+using System.Collections.Generic;
 using System.Diagnostics.Contracts;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 
 namespace Squidex.Domain.Apps.Core.Apps
 {
-    public sealed class AppContributors : DictionaryWrapper<string, string>
+    public sealed class AppContributors : ArrayDictionary<string, string>
     {
         public static readonly AppContributors Empty = new AppContributors();
 
         private AppContributors()
-            : base(ImmutableDictionary<string, string>.Empty)
         {
         }
 
-        public AppContributors(ImmutableDictionary<string, string> inner)
-            : base(inner)
+        public AppContributors(KeyValuePair<string, string>[] items)
+            : base(items)
         {
         }
 
@@ -31,7 +31,7 @@ namespace Squidex.Domain.Apps.Core.Apps
             Guard.NotNullOrEmpty(contributorId, nameof(contributorId));
             Guard.NotNullOrEmpty(role, nameof(role));
 
-            return new AppContributors(Inner.SetItem(contributorId, role));
+            return new AppContributors(With(contributorId, role));
         }
 
         [Pure]
@@ -39,7 +39,7 @@ namespace Squidex.Domain.Apps.Core.Apps
         {
             Guard.NotNullOrEmpty(contributorId, nameof(contributorId));
 
-            return new AppContributors(Inner.Remove(contributorId));
+            return new AppContributors(Without(contributorId));
         }
     }
 }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Apps/AppPatterns.cs b/src/Squidex.Domain.Apps.Core.Model/Apps/AppPatterns.cs
index e0ce032e3..cb9e13d3d 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Apps/AppPatterns.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Apps/AppPatterns.cs
@@ -4,39 +4,45 @@
 //  Copyright (c) Squidex UG (haftungsbeschränkt)
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
+
 using System;
-using System.Collections.Immutable;
+using System.Collections.Generic;
 using System.Diagnostics.Contracts;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 
 namespace Squidex.Domain.Apps.Core.Apps
 {
-    public sealed class AppPatterns : DictionaryWrapper<Guid, AppPattern>
+    public sealed class AppPatterns : ArrayDictionary<Guid, AppPattern>
     {
         public static readonly AppPatterns Empty = new AppPatterns();
 
         private AppPatterns()
-            : base(ImmutableDictionary<Guid, AppPattern>.Empty)
         {
         }
 
-        public AppPatterns(ImmutableDictionary<Guid, AppPattern> inner)
-            : base(inner)
+        public AppPatterns(KeyValuePair<Guid, AppPattern>[] items)
+            : base(items)
         {
         }
 
         [Pure]
-        public AppPatterns Add(Guid id, string name, string pattern, string message)
+        public AppPatterns Remove(Guid id)
         {
-            var newPattern = new AppPattern(name, pattern, message);
-
-            return new AppPatterns(Inner.Add(id, newPattern));
+            return new AppPatterns(Without(id));
         }
 
         [Pure]
-        public AppPatterns Remove(Guid id)
+        public AppPatterns Add(Guid id, string name, string pattern, string message)
         {
-            return new AppPatterns(Inner.Remove(id));
+            var newPattern = new AppPattern(name, pattern, message);
+
+            if (ContainsKey(id))
+            {
+                throw new ArgumentException("Id already exists.", nameof(id));
+            }
+
+            return new AppPatterns(With(id, newPattern));
         }
 
         [Pure]
@@ -50,7 +56,7 @@ namespace Squidex.Domain.Apps.Core.Apps
                 return this;
             }
 
-            return new AppPatterns(Inner.SetItem(id, appPattern.Update(name, pattern, message)));
+            return new AppPatterns(With(id, appPattern.Update(name, pattern, message)));
         }
     }
 }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppClientsConverter.cs b/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppClientsConverter.cs
index 3da12f586..bde833f22 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppClientsConverter.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppClientsConverter.cs
@@ -7,7 +7,7 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
+using System.Linq;
 using Newtonsoft.Json;
 using Squidex.Infrastructure.Json;
 
@@ -31,7 +31,12 @@ namespace Squidex.Domain.Apps.Core.Apps.Json
         {
             var json = serializer.Deserialize<Dictionary<string, JsonAppClient>>(reader);
 
-            return new AppClients(json.ToImmutableDictionary(x => x.Key, x => x.Value.ToClient()));
+            return new AppClients(json.Select(Convert).ToArray());
+        }
+
+        private static KeyValuePair<string, AppClient> Convert(KeyValuePair<string, JsonAppClient> kvp)
+        {
+            return new KeyValuePair<string, AppClient>(kvp.Key, kvp.Value.ToClient());
         }
     }
 }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppContributorsConverter.cs b/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppContributorsConverter.cs
index b3955699f..997bcfe11 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppContributorsConverter.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppContributorsConverter.cs
@@ -7,7 +7,7 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
+using System.Linq;
 using Newtonsoft.Json;
 using Squidex.Infrastructure.Json;
 
@@ -31,7 +31,7 @@ namespace Squidex.Domain.Apps.Core.Apps.Json
         {
             var json = serializer.Deserialize<Dictionary<string, string>>(reader);
 
-            return new AppContributors(json.ToImmutableDictionary());
+            return new AppContributors(json.ToArray());
         }
     }
 }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppPatternsConverter.cs b/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppPatternsConverter.cs
index 20ae7248c..34a23812e 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppPatternsConverter.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Apps/Json/AppPatternsConverter.cs
@@ -4,9 +4,10 @@
 //  Copyright (c) Squidex UG (haftungsbeschränkt)
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
+
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
+using System.Linq;
 using Newtonsoft.Json;
 using Squidex.Infrastructure.Json;
 
@@ -30,7 +31,12 @@ namespace Squidex.Domain.Apps.Core.Apps.Json
         {
             var json = serializer.Deserialize<Dictionary<Guid, JsonAppPattern>>(reader);
 
-            return new AppPatterns(json.ToImmutableDictionary(x => x.Key, x => x.Value.ToPattern()));
+            return new AppPatterns(json.Select(Convert).ToArray());
+        }
+
+        private static KeyValuePair<Guid, AppPattern> Convert(KeyValuePair<Guid, JsonAppPattern> kvp)
+        {
+            return new KeyValuePair<Guid, AppPattern>(kvp.Key, kvp.Value.ToPattern());
         }
     }
 }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Apps/Json/RolesConverter.cs b/src/Squidex.Domain.Apps.Core.Model/Apps/Json/RolesConverter.cs
index b33285923..043c2b4af 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Apps/Json/RolesConverter.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Apps/Json/RolesConverter.cs
@@ -10,7 +10,6 @@ using Squidex.Infrastructure.Json;
 using Squidex.Infrastructure.Security;
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Linq;
 
 namespace Squidex.Domain.Apps.Core.Apps.Json
@@ -33,7 +32,12 @@ namespace Squidex.Domain.Apps.Core.Apps.Json
         {
             var json = serializer.Deserialize<Dictionary<string, string[]>>(reader);
 
-            return new Roles(json.ToImmutableDictionary(x => x.Key, x => new Role(x.Key, new PermissionSet(x.Value))));
+            return new Roles(json.Select(Convert).ToArray());
+        }
+
+        private static KeyValuePair<string, Role> Convert(KeyValuePair<string, string[]> kvp)
+        {
+            return new KeyValuePair<string, Role>(kvp.Key, new Role(kvp.Key, new PermissionSet(kvp.Value)));
         }
     }
 }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Apps/LanguageConfig.cs b/src/Squidex.Domain.Apps.Core.Model/Apps/LanguageConfig.cs
index 05ce64873..ac4bffde9 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Apps/LanguageConfig.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Apps/LanguageConfig.cs
@@ -14,7 +14,6 @@ namespace Squidex.Domain.Apps.Core.Apps
 {
     public sealed class LanguageConfig : IFieldPartitionItem
     {
-        private static readonly Language[] DefaultFallback = Array.Empty<Language>();
         private readonly Language language;
         private readonly Language[] languageFallbacks;
 
@@ -57,7 +56,7 @@ namespace Squidex.Domain.Apps.Core.Apps
             IsOptional = isOptional;
 
             this.language = language;
-            this.languageFallbacks = fallback ?? DefaultFallback;
+            this.languageFallbacks = fallback ?? Array.Empty<Language>();
         }
     }
 }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Apps/LanguagesConfig.cs b/src/Squidex.Domain.Apps.Core.Model/Apps/LanguagesConfig.cs
index 51003278f..8a9d6febe 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Apps/LanguagesConfig.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Apps/LanguagesConfig.cs
@@ -8,10 +8,10 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Diagnostics.Contracts;
 using System.Linq;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 
 namespace Squidex.Domain.Apps.Core.Apps
 {
@@ -19,7 +19,7 @@ namespace Squidex.Domain.Apps.Core.Apps
     {
         public static readonly LanguagesConfig English = Build(Language.EN);
 
-        private readonly ImmutableDictionary<Language, LanguageConfig> languages;
+        private readonly ArrayDictionary<Language, LanguageConfig> languages;
         private readonly LanguageConfig master;
 
         public LanguageConfig Master
@@ -47,7 +47,7 @@ namespace Squidex.Domain.Apps.Core.Apps
             get { return languages.Count; }
         }
 
-        private LanguagesConfig(ImmutableDictionary<Language, LanguageConfig> languages, LanguageConfig master, bool checkMaster = true)
+        private LanguagesConfig(ArrayDictionary<Language, LanguageConfig> languages, LanguageConfig master, bool checkMaster = true)
         {
             if (checkMaster)
             {
@@ -74,7 +74,7 @@ namespace Squidex.Domain.Apps.Core.Apps
         {
             Guard.NotNull(configs, nameof(configs));
 
-            return new LanguagesConfig(configs.ToImmutableDictionary(x => x.Language), configs.FirstOrDefault());
+            return new LanguagesConfig(configs.ToArrayDictionary(x => x.Language), configs.FirstOrDefault());
         }
 
         public static LanguagesConfig Build(params LanguageConfig[] configs)
@@ -100,7 +100,12 @@ namespace Squidex.Domain.Apps.Core.Apps
         {
             Guard.NotNull(config, nameof(config));
 
-            return new LanguagesConfig(languages.SetItem(config.Language, config), Master?.Language == config.Language ? config : Master);
+            var newLanguages =
+                new ArrayDictionary<Language, LanguageConfig>(languages.With(config.Language, config));
+
+            var newMaster = Master?.Language == config.Language ? config : Master;
+
+            return new LanguagesConfig(newLanguages, newMaster);
         }
 
         [Pure]
@@ -114,7 +119,7 @@ namespace Squidex.Domain.Apps.Core.Apps
                         config.Language,
                         config.IsOptional,
                         config.LanguageFallbacks.Except(new[] { language })))
-                    .ToImmutableDictionary(x => x.Language);
+                    .ToArrayDictionary(x => x.Language);
 
             var newMaster =
                 newLanguages.Values.FirstOrDefault(x => x.Language == Master.Language) ??
diff --git a/src/Squidex.Domain.Apps.Core.Model/Apps/Roles.cs b/src/Squidex.Domain.Apps.Core.Model/Apps/Roles.cs
index 3c0320f10..58e7c5bfa 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Apps/Roles.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Apps/Roles.cs
@@ -6,38 +6,44 @@
 // ==========================================================================
 
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
+using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Diagnostics.Contracts;
+using System.Linq;
 
 namespace Squidex.Domain.Apps.Core.Apps
 {
-    public sealed class Roles : DictionaryWrapper<string, Role>
+    public sealed class Roles : ArrayDictionary<string, Role>
     {
         public static readonly Roles Empty = new Roles();
 
         private Roles()
-            : base(ImmutableDictionary<string, Role>.Empty)
         {
         }
 
-        public Roles(ImmutableDictionary<string, Role> inner)
-            : base(inner)
+        public Roles(KeyValuePair<string, Role>[] items)
+            : base(items)
         {
         }
 
         [Pure]
-        public Roles Add(string name)
+        public Roles Remove(string name)
         {
-            var newRole = new Role(name);
-
-            return new Roles(Inner.Add(name, newRole));
+            return new Roles(Without(name));
         }
 
         [Pure]
-        public Roles Remove(string name)
+        public Roles Add(string name)
         {
-            return new Roles(Inner.Remove(name));
+            var newRole = new Role(name);
+
+            if (ContainsKey(name))
+            {
+                throw new ArgumentException("Name already exists.", nameof(name));
+            }
+
+            return new Roles(With(name, newRole));
         }
 
         [Pure]
@@ -51,7 +57,7 @@ namespace Squidex.Domain.Apps.Core.Apps
                 return this;
             }
 
-            return new Roles(Inner.SetItem(name, role.Update(permissions)));
+            return new Roles(With(name, role.Update(permissions)));
         }
 
         public static Roles CreateDefaults(string app)
@@ -63,7 +69,7 @@ namespace Squidex.Domain.Apps.Core.Apps
                     [Role.Editor] = Role.CreateEditor(app),
                     [Role.Owner] = Role.CreateOwner(app),
                     [Role.Reader] = Role.CreateReader(app)
-                }.ToImmutableDictionary());
+                }.ToArray());
         }
     }
 }
diff --git a/src/Squidex.Domain.Apps.Core.Model/DictionaryWrapper{TKey,TValue}.cs b/src/Squidex.Domain.Apps.Core.Model/DictionaryWrapper{TKey,TValue}.cs
deleted file mode 100644
index ee96809e0..000000000
--- a/src/Squidex.Domain.Apps.Core.Model/DictionaryWrapper{TKey,TValue}.cs
+++ /dev/null
@@ -1,68 +0,0 @@
-// ==========================================================================
-//  Squidex Headless CMS
-// ==========================================================================
-//  Copyright (c) Squidex UG (haftungsbeschränkt)
-//  All rights reserved. Licensed under the MIT license.
-// ==========================================================================
-
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.Immutable;
-
-namespace Squidex.Domain.Apps.Core
-{
-    public abstract class DictionaryWrapper<TKey, TValue> : IReadOnlyDictionary<TKey, TValue>
-    {
-        private readonly ImmutableDictionary<TKey, TValue> inner;
-
-        public TValue this[TKey key]
-        {
-            get { return inner[key]; }
-        }
-
-        public IEnumerable<TKey> Keys
-        {
-            get { return inner.Keys; }
-        }
-
-        public IEnumerable<TValue> Values
-        {
-            get { return inner.Values; }
-        }
-
-        public int Count
-        {
-            get { return inner.Count; }
-        }
-
-        protected ImmutableDictionary<TKey, TValue> Inner
-        {
-            get { return inner; }
-        }
-
-        protected DictionaryWrapper(ImmutableDictionary<TKey, TValue> inner)
-        {
-            this.inner = inner;
-        }
-
-        public bool ContainsKey(TKey key)
-        {
-            return inner.ContainsKey(key);
-        }
-
-        public bool TryGetValue(TKey key, out TValue value)
-        {
-            return inner.TryGetValue(key, out value);
-        }
-
-        IEnumerator<KeyValuePair<TKey, TValue>> IEnumerable<KeyValuePair<TKey, TValue>>.GetEnumerator()
-        {
-            return inner.GetEnumerator();
-        }
-
-        IEnumerator IEnumerable.GetEnumerator()
-        {
-            return inner.GetEnumerator();
-        }
-    }
-}
diff --git a/src/Squidex.Domain.Apps.Core.Model/Rules/Triggers/ContentChangedTrigger.cs b/src/Squidex.Domain.Apps.Core.Model/Rules/Triggers/ContentChangedTrigger.cs
index e62138920..a4db365a5 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Rules/Triggers/ContentChangedTrigger.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Rules/Triggers/ContentChangedTrigger.cs
@@ -5,15 +5,15 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
 using Squidex.Infrastructure;
+using System.Collections.ObjectModel;
 
 namespace Squidex.Domain.Apps.Core.Rules.Triggers
 {
     [TypeName(nameof(ContentChangedTrigger))]
     public sealed class ContentChangedTrigger : RuleTrigger
     {
-        public ImmutableList<ContentChangedTriggerSchema> Schemas { get; set; }
+        public ReadOnlyCollection<ContentChangedTriggerSchema> Schemas { get; set; }
 
         public bool HandleAll { get; set; }
 
diff --git a/src/Squidex.Domain.Apps.Core.Model/Schemas/AssetsFieldProperties.cs b/src/Squidex.Domain.Apps.Core.Model/Schemas/AssetsFieldProperties.cs
index 2e39adc21..0cc74af29 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Schemas/AssetsFieldProperties.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Schemas/AssetsFieldProperties.cs
@@ -5,8 +5,8 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
 using Squidex.Infrastructure;
+using System.Collections.ObjectModel;
 
 namespace Squidex.Domain.Apps.Core.Schemas
 {
@@ -35,7 +35,7 @@ namespace Squidex.Domain.Apps.Core.Schemas
 
         public int? AspectHeight { get; set; }
 
-        public ImmutableList<string> AllowedExtensions { get; set; }
+        public ReadOnlyCollection<string> AllowedExtensions { get; set; }
 
         public override T Accept<T>(IFieldPropertiesVisitor<T> visitor)
         {
diff --git a/src/Squidex.Domain.Apps.Core.Model/Schemas/FieldCollection.cs b/src/Squidex.Domain.Apps.Core.Model/Schemas/FieldCollection.cs
index e1546841d..c4c6627f1 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Schemas/FieldCollection.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Schemas/FieldCollection.cs
@@ -7,7 +7,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Diagnostics.Contracts;
 using System.Linq;
 using Squidex.Infrastructure;
@@ -17,10 +16,13 @@ namespace Squidex.Domain.Apps.Core.Schemas
     public sealed class FieldCollection<T> : Cloneable<FieldCollection<T>> where T : IField
     {
         public static readonly FieldCollection<T> Empty = new FieldCollection<T>();
+        
+        private static readonly Dictionary<long, T> EmptyById = new Dictionary<long, T>();
+        private static readonly Dictionary<string, T> EmptyByString = new Dictionary<string, T>();
 
-        private ImmutableArray<T> fieldsOrdered = ImmutableArray<T>.Empty;
-        private ImmutableDictionary<long, T> fieldsById;
-        private ImmutableDictionary<string, T> fieldsByName;
+        private T[] fieldsOrdered;
+        private Dictionary<long, T> fieldsById;
+        private Dictionary<string, T> fieldsByName;
 
         public IReadOnlyList<T> Ordered
         {
@@ -35,11 +37,11 @@ namespace Squidex.Domain.Apps.Core.Schemas
                 {
                     if (fieldsOrdered.Length == 0)
                     {
-                        fieldsById = ImmutableDictionary<long, T>.Empty;
+                        fieldsById = EmptyById;
                     }
                     else
                     {
-                        fieldsById = fieldsOrdered.ToImmutableDictionary(x => x.Id);
+                        fieldsById = fieldsOrdered.ToDictionary(x => x.Id);
                     }
                 }
 
@@ -55,11 +57,11 @@ namespace Squidex.Domain.Apps.Core.Schemas
                 {
                     if (fieldsOrdered.Length == 0)
                     {
-                        fieldsByName = ImmutableDictionary<string, T>.Empty;
+                        fieldsByName = EmptyByString;
                     }
                     else
                     {
-                        fieldsByName = fieldsOrdered.ToImmutableDictionary(x => x.Name, StringComparer.OrdinalIgnoreCase);
+                        fieldsByName = fieldsOrdered.ToDictionary(x => x.Name, StringComparer.OrdinalIgnoreCase);
                     }
                 }
 
@@ -69,13 +71,14 @@ namespace Squidex.Domain.Apps.Core.Schemas
 
         private FieldCollection()
         {
+            fieldsOrdered = Array.Empty<T>();
         }
 
         public FieldCollection(T[] fields)
         {
             Guard.NotNull(fields, nameof(fields));
 
-            fieldsOrdered = ImmutableArray.Create(fields);
+            fieldsOrdered = fields;
         }
 
         protected override void OnCloned()
@@ -94,7 +97,7 @@ namespace Squidex.Domain.Apps.Core.Schemas
 
             return Clone(clone =>
             {
-                clone.fieldsOrdered = fieldsOrdered.Remove(field);
+                clone.fieldsOrdered = fieldsOrdered.Where(x => x.Id != fieldId).ToArray();
             });
         }
 
@@ -110,7 +113,7 @@ namespace Squidex.Domain.Apps.Core.Schemas
 
             return Clone(clone =>
             {
-                clone.fieldsOrdered = fieldsOrdered.OrderBy(f => ids.IndexOf(f.Id)).ToImmutableArray();
+                clone.fieldsOrdered = fieldsOrdered.OrderBy(f => ids.IndexOf(f.Id)).ToArray();
             });
         }
 
@@ -126,7 +129,7 @@ namespace Squidex.Domain.Apps.Core.Schemas
 
             return Clone(clone =>
             {
-                clone.fieldsOrdered = clone.fieldsOrdered.Add(field);
+                clone.fieldsOrdered = clone.fieldsOrdered.Union(Enumerable.Repeat(field, 1)).ToArray();
             });
         }
 
@@ -154,7 +157,7 @@ namespace Squidex.Domain.Apps.Core.Schemas
 
             return Clone(clone =>
             {
-                clone.fieldsOrdered = clone.fieldsOrdered.Replace(field, typedField);
+                clone.fieldsOrdered = clone.fieldsOrdered.Select(x => ReferenceEquals(x, field) ? newField : x).ToArray();
             });
         }
     }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonFieldModel.cs b/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonFieldModel.cs
index ebd6f722f..d199a2497 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonFieldModel.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonFieldModel.cs
@@ -6,6 +6,10 @@
 // ==========================================================================
 
 using Newtonsoft.Json;
+using Squidex.Infrastructure;
+using System;
+using System.Linq;
+using P = Squidex.Domain.Apps.Core.Partitioning;
 
 namespace Squidex.Domain.Apps.Core.Schemas.Json
 {
@@ -34,5 +38,21 @@ namespace Squidex.Domain.Apps.Core.Schemas.Json
 
         [JsonProperty]
         public JsonNestedFieldModel[] Children { get; set; }
+
+        public RootField ToField()
+        {
+            var partitioning = P.FromString(Partitioning);
+
+            if (Properties is ArrayFieldProperties arrayProperties)
+            {
+                var nested = Children?.ToArray(n => n.ToNestedField()) ?? Array.Empty<NestedField>();
+
+                return new ArrayField(Id, Name, partitioning, nested, arrayProperties, this);
+            }
+            else
+            {
+                return Properties.CreateRootField(Id, Name, partitioning, this);
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonNestedFieldModel.cs b/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonNestedFieldModel.cs
index 50240e695..c7a42baaa 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonNestedFieldModel.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonNestedFieldModel.cs
@@ -30,5 +30,10 @@ namespace Squidex.Domain.Apps.Core.Schemas.Json
         {
             get { return false; }
         }
+
+        public NestedField ToNestedField()
+        {
+            return Properties.CreateNestedField(Id, Name, this);
+        }
     }
 }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonSchemaModel.cs b/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonSchemaModel.cs
index 7e27ef756..4b0b9e917 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonSchemaModel.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/JsonSchemaModel.cs
@@ -14,8 +14,6 @@ namespace Squidex.Domain.Apps.Core.Schemas.Json
 {
     public sealed class JsonSchemaModel
     {
-        private static readonly RootField[] Empty = Array.Empty<RootField>();
-
         [JsonProperty]
         public string Name { get; set; }
 
@@ -73,35 +71,9 @@ namespace Squidex.Domain.Apps.Core.Schemas.Json
             return null;
         }
 
-        public Schema ToSchema(FieldRegistry registry)
+        public Schema ToSchema()
         {
-            var fields = Empty;
-
-            if (Fields != null)
-            {
-                fields = Fields.ToArray(fieldModel =>
-                {
-                    var parititonKey = new Partitioning(fieldModel.Partitioning);
-
-                    RootField field;
-
-                    if (fieldModel.Properties is ArrayFieldProperties arrayProperties && fieldModel.Children?.Length > 0)
-                    {
-                        var nestedFields = fieldModel.Children.ToArray(nestedFieldModel =>
-                        {
-                            return registry.CreateNestedField(nestedFieldModel.Id, nestedFieldModel.Name, nestedFieldModel.Properties, nestedFieldModel);
-                        });
-
-                        field = new ArrayField(fieldModel.Id, fieldModel.Name, parititonKey, nestedFields, arrayProperties, fieldModel);
-                    }
-                    else
-                    {
-                        field = registry.CreateRootField(fieldModel.Id, fieldModel.Name, parititonKey, fieldModel.Properties, fieldModel);
-                    }
-
-                    return field;
-                });
-            }
+            var fields = Fields.ToArray(f => f.ToField()) ?? Array.Empty<RootField>();
 
             return new Schema(Name, fields, Properties, IsPublished);
         }
diff --git a/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/SchemaConverter.cs b/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/SchemaConverter.cs
index 356f5bb1d..3ca34038b 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/SchemaConverter.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Schemas/Json/SchemaConverter.cs
@@ -14,15 +14,6 @@ namespace Squidex.Domain.Apps.Core.Schemas.Json
 {
     public sealed class SchemaConverter : JsonClassConverter<Schema>
     {
-        private readonly FieldRegistry fieldRegistry;
-
-        public SchemaConverter(FieldRegistry fieldRegistry)
-        {
-            Guard.NotNull(fieldRegistry, nameof(fieldRegistry));
-
-            this.fieldRegistry = fieldRegistry;
-        }
-
         protected override void WriteValue(JsonWriter writer, Schema value, JsonSerializer serializer)
         {
             serializer.Serialize(writer, new JsonSchemaModel(value));
@@ -30,7 +21,7 @@ namespace Squidex.Domain.Apps.Core.Schemas.Json
 
         protected override Schema ReadValue(JsonReader reader, Type objectType, JsonSerializer serializer)
         {
-            return serializer.Deserialize<JsonSchemaModel>(reader).ToSchema(fieldRegistry);
+            return serializer.Deserialize<JsonSchemaModel>(reader).ToSchema();
         }
     }
 }
\ No newline at end of file
diff --git a/src/Squidex.Domain.Apps.Core.Model/Schemas/NumberFieldProperties.cs b/src/Squidex.Domain.Apps.Core.Model/Schemas/NumberFieldProperties.cs
index e16a47f28..f4df67c4d 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Schemas/NumberFieldProperties.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Schemas/NumberFieldProperties.cs
@@ -5,15 +5,15 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
 using Squidex.Infrastructure;
+using System.Collections.ObjectModel;
 
 namespace Squidex.Domain.Apps.Core.Schemas
 {
     [TypeName("NumberField")]
     public sealed class NumberFieldProperties : FieldProperties
     {
-        public ImmutableList<double> AllowedValues { get; set; }
+        public ReadOnlyCollection<double> AllowedValues { get; set; }
 
         public double? MaxValue { get; set; }
 
diff --git a/src/Squidex.Domain.Apps.Core.Model/Schemas/StringFieldProperties.cs b/src/Squidex.Domain.Apps.Core.Model/Schemas/StringFieldProperties.cs
index eaee1f7a5..e5c6d3fd6 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Schemas/StringFieldProperties.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Schemas/StringFieldProperties.cs
@@ -5,15 +5,15 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
 using Squidex.Infrastructure;
+using System.Collections.ObjectModel;
 
 namespace Squidex.Domain.Apps.Core.Schemas
 {
     [TypeName("StringField")]
     public sealed class StringFieldProperties : FieldProperties
     {
-        public ImmutableList<string> AllowedValues { get; set; }
+        public ReadOnlyCollection<string> AllowedValues { get; set; }
 
         public int? MinLength { get; set; }
 
diff --git a/src/Squidex.Domain.Apps.Core.Model/Schemas/TagsFieldProperties.cs b/src/Squidex.Domain.Apps.Core.Model/Schemas/TagsFieldProperties.cs
index a1c1f822e..aeaf2074a 100644
--- a/src/Squidex.Domain.Apps.Core.Model/Schemas/TagsFieldProperties.cs
+++ b/src/Squidex.Domain.Apps.Core.Model/Schemas/TagsFieldProperties.cs
@@ -6,14 +6,14 @@
 // ==========================================================================
 
 using Squidex.Infrastructure;
-using System.Collections.Immutable;
+using System.Collections.ObjectModel;
 
 namespace Squidex.Domain.Apps.Core.Schemas
 {
     [TypeName("TagsField")]
     public sealed class TagsFieldProperties : FieldProperties
     {
-        public ImmutableList<string> AllowedValues { get; set; }
+        public ReadOnlyCollection<string> AllowedValues { get; set; }
 
         public int? MinItems { get; set; }
 
diff --git a/src/Squidex.Domain.Apps.Entities/Apps/Templates/Builders/StringFieldBuilder.cs b/src/Squidex.Domain.Apps.Entities/Apps/Templates/Builders/StringFieldBuilder.cs
index 4a798f72b..0fd4b857b 100644
--- a/src/Squidex.Domain.Apps.Entities/Apps/Templates/Builders/StringFieldBuilder.cs
+++ b/src/Squidex.Domain.Apps.Entities/Apps/Templates/Builders/StringFieldBuilder.cs
@@ -5,9 +5,9 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
 using Squidex.Domain.Apps.Core.Schemas;
 using Squidex.Domain.Apps.Entities.Schemas.Commands;
+using Squidex.Infrastructure.Collections;
 
 namespace Squidex.Domain.Apps.Entities.Apps.Templates.Builders
 {
@@ -34,7 +34,7 @@ namespace Squidex.Domain.Apps.Entities.Apps.Templates.Builders
 
         public StringFieldBuilder AsDropDown(params string[] values)
         {
-            Properties<StringFieldProperties>().AllowedValues = ImmutableList.Create(values);
+            Properties<StringFieldProperties>().AllowedValues = ReadOnlyCollection.Create(values);
             Properties<StringFieldProperties>().Editor = StringFieldEditor.Dropdown;
 
             return this;
diff --git a/src/Squidex.Infrastructure/CollectionExtensions.cs b/src/Squidex.Infrastructure/CollectionExtensions.cs
index 1d26ce8b4..442cb65a2 100644
--- a/src/Squidex.Infrastructure/CollectionExtensions.cs
+++ b/src/Squidex.Infrastructure/CollectionExtensions.cs
@@ -7,7 +7,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Linq;
 
 namespace Squidex.Infrastructure
@@ -21,37 +20,6 @@ namespace Squidex.Infrastructure
             return enumerable.OrderBy(x => random.Next()).ToList();
         }
 
-        public static ImmutableDictionary<TKey, TValue> SetItem<TKey, TValue>(this ImmutableDictionary<TKey, TValue> dictionary, TKey key, Func<TValue, TValue> updater)
-        {
-            if (dictionary.TryGetValue(key, out var value))
-            {
-                var newValue = updater(value);
-
-                if (!Equals(newValue, value))
-                {
-                    return dictionary.SetItem(key, newValue);
-                }
-            }
-
-            return dictionary;
-        }
-
-        public static bool TryGetValue<TKey, TValue, TBase>(this IReadOnlyDictionary<TKey, TValue> values, TKey key, out TBase item) where TValue : TBase
-        {
-            if (values.TryGetValue(key, out var value))
-            {
-                item = value;
-
-                return true;
-            }
-            else
-            {
-                item = default(TBase);
-
-                return false;
-            }
-        }
-
         public static IEnumerable<T> OrEmpty<T>(this IEnumerable<T> source)
         {
             return source ?? Enumerable.Empty<T>();
diff --git a/src/Squidex.Infrastructure/Collections/ArrayDictionary.cs b/src/Squidex.Infrastructure/Collections/ArrayDictionary.cs
new file mode 100644
index 000000000..1a6f1afd2
--- /dev/null
+++ b/src/Squidex.Infrastructure/Collections/ArrayDictionary.cs
@@ -0,0 +1,21 @@
+// ==========================================================================
+//  Squidex Headless CMS
+// ==========================================================================
+//  Copyright (c) Squidex UG (haftungsbeschraenkt)
+//  All rights reserved. Licensed under the MIT license.
+// ==========================================================================
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Squidex.Infrastructure.Collections
+{
+    public static class ArrayDictionary
+    {
+        public static ArrayDictionary<TKey, TValue> ToArrayDictionary<TKey, TValue>(this IEnumerable<TValue> source, Func<TValue, TKey> keyExtractor)
+        {
+            return new ArrayDictionary<TKey, TValue>(source.Select(x => new KeyValuePair<TKey, TValue>(keyExtractor(x), x)).ToArray());
+        }
+    }
+}
diff --git a/src/Squidex.Infrastructure/Collections/ArrayDictionary{TKey,TValue}.cs b/src/Squidex.Infrastructure/Collections/ArrayDictionary{TKey,TValue}.cs
new file mode 100644
index 000000000..30f1adc90
--- /dev/null
+++ b/src/Squidex.Infrastructure/Collections/ArrayDictionary{TKey,TValue}.cs
@@ -0,0 +1,163 @@
+// ==========================================================================
+//  Squidex Headless CMS
+// ==========================================================================
+//  Copyright (c) Squidex UG (haftungsbeschränkt)
+//  All rights reserved. Licensed under the MIT license.
+// ==========================================================================
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Squidex.Infrastructure.Collections
+{
+    public class ArrayDictionary<TKey, TValue> : IReadOnlyDictionary<TKey, TValue>
+    {
+        private readonly IEqualityComparer<TKey> keyComparer;
+        private readonly KeyValuePair<TKey, TValue>[] items;
+
+        public TValue this[TKey key]
+        {
+            get
+            {
+                if (!TryGetValue(key, out var value))
+                {
+                    throw new KeyNotFoundException();
+                }
+
+                return value;
+            }
+        }
+
+        public IEnumerable<TKey> Keys
+        {
+            get { return items.Select(x => x.Key); }
+        }
+
+        public IEnumerable<TValue> Values
+        {
+            get { return items.Select(x => x.Value); }
+        }
+
+        public int Count
+        {
+            get { return items.Length; }
+        }
+
+        public ArrayDictionary()
+            : this(EqualityComparer<TKey>.Default, Array.Empty<KeyValuePair<TKey, TValue>>())
+        {
+        }
+
+        public ArrayDictionary(KeyValuePair<TKey, TValue>[] items)
+            : this(EqualityComparer<TKey>.Default, items)
+        {
+        }
+
+        public ArrayDictionary(IEqualityComparer<TKey> keyComparer, KeyValuePair<TKey, TValue>[] items)
+        {
+            Guard.NotNull(items, nameof(items));
+            Guard.NotNull(keyComparer, nameof(keyComparer));
+
+            this.items = items;
+
+            this.keyComparer = keyComparer;
+        }
+
+        public KeyValuePair<TKey, TValue>[] With(TKey key, TValue value)
+        {
+            var result = new List<KeyValuePair<TKey, TValue>>(Math.Max(items.Length, 1));
+
+            var wasReplaced = false;
+
+            for (var i = 0; i < items.Length; i++)
+            {
+                var item = items[i];
+
+                if (wasReplaced || !keyComparer.Equals(item.Key, key))
+                {
+                    result.Add(item);
+                }
+                else
+                {
+                    result.Add(new KeyValuePair<TKey, TValue>(key, value));
+                    wasReplaced = true;
+                }
+            }
+
+            if (!wasReplaced)
+            {
+                result.Add(new KeyValuePair<TKey, TValue>(key, value));
+            }
+
+            return result.ToArray();
+        }
+
+        public KeyValuePair<TKey, TValue>[] Without(TKey key)
+        {
+            var result = new List<KeyValuePair<TKey, TValue>>(Math.Max(items.Length, 1));
+
+            var wasRemoved = false;
+
+            for (var i = 0; i < items.Length; i++)
+            {
+                var item = items[i];
+
+                if (wasRemoved || !keyComparer.Equals(item.Key, key))
+                {
+                    result.Add(item);
+                }
+                else
+                {
+                    wasRemoved = true;
+                }
+            }
+
+            return result.ToArray();
+        }
+
+        public bool ContainsKey(TKey key)
+        {
+            for (var i = 0; i < items.Length; i++)
+            {
+                if (keyComparer.Equals(items[i].Key, key))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        public bool TryGetValue(TKey key, out TValue value)
+        {
+            for (var i = 0; i < items.Length; i++)
+            {
+                if (keyComparer.Equals(items[i].Key, key))
+                {
+                    value = items[i].Value;
+                    return true;
+                }
+            }
+
+            value = default(TValue);
+            return false;
+        }
+
+        IEnumerator<KeyValuePair<TKey, TValue>> IEnumerable<KeyValuePair<TKey, TValue>>.GetEnumerator()
+        {
+            return GetEnumerable(items).GetEnumerator();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return items.GetEnumerator();
+        }
+
+        private static IEnumerable<T2> GetEnumerable<T2>(T2[] array)
+        {
+            return array;
+        }
+    }
+}
diff --git a/src/Squidex.Infrastructure/Collections/ReadOnlyCollection.cs b/src/Squidex.Infrastructure/Collections/ReadOnlyCollection.cs
new file mode 100644
index 000000000..83466a3a0
--- /dev/null
+++ b/src/Squidex.Infrastructure/Collections/ReadOnlyCollection.cs
@@ -0,0 +1,36 @@
+// ==========================================================================
+//  Squidex Headless CMS
+// ==========================================================================
+//  Copyright (c) Squidex UG (haftungsbeschraenkt)
+//  All rights reserved. Licensed under the MIT license.
+// ==========================================================================
+
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+
+namespace Squidex.Infrastructure.Collections
+{
+    public static class ReadOnlyCollection
+    {
+        private static class Empties<T>
+        {
+            public static readonly ReadOnlyCollection<T> Collection = new ReadOnlyCollection<T>(new List<T>());
+        }
+
+        public static ReadOnlyCollection<T> Create<T>(params T[] items)
+        {
+            return new ReadOnlyCollection<T>(items.ToList());
+        }
+
+        public static ReadOnlyCollection<T> Empty<T>()
+        {
+            return Empties<T>.Collection;
+        }
+
+        public static ReadOnlyCollection<T> ToReadOnlyCollection<T>(this IEnumerable<T> source)
+        {
+            return new ReadOnlyCollection<T>(source.ToList());
+        }
+    }
+}
diff --git a/src/Squidex.Infrastructure/StringExtensions.cs b/src/Squidex.Infrastructure/StringExtensions.cs
index 55349977a..41b23ac9e 100644
--- a/src/Squidex.Infrastructure/StringExtensions.cs
+++ b/src/Squidex.Infrastructure/StringExtensions.cs
@@ -15,6 +15,7 @@ namespace Squidex.Infrastructure
 {
     public static class StringExtensions
     {
+        private const char NullChar = (char)0;
         private static readonly Regex SlugRegex = new Regex("^[a-z0-9]+(\\-[a-z0-9]+)*$", RegexOptions.Compiled);
         private static readonly Regex PropertyNameRegex = new Regex("^[a-zA-Z0-9]+(\\-[a-zA-Z0-9]+)*$", RegexOptions.Compiled);
         private static readonly Dictionary<char, string> LowerCaseDiacritics;
@@ -325,36 +326,97 @@ namespace Squidex.Infrastructure
 
         public static string ToPascalCase(this string value)
         {
+            if (string.IsNullOrWhiteSpace(value))
+            {
+                return string.Empty;
+            }
+
             var sb = new StringBuilder();
 
-            foreach (var part in value.Split(new[] { '-', '_', ' ' }, StringSplitOptions.RemoveEmptyEntries))
+            var last = NullChar;
+            var length = 0;
+
+            for (var i = 0; i < value.Length; i++)
             {
-                if (part.Length < 2)
+                var c = value[i];
+
+                if (c == '-' || c == '_' || c == ' ')
                 {
-                    sb.Append(part.ToUpper());
+                    if (last != NullChar)
+                    {
+                        sb.Append(char.ToUpperInvariant(last));
+                    }
+
+                    last = NullChar;
+                    length = 0;
                 }
                 else
                 {
-                    sb.Append(char.ToUpper(part[0]));
-                    sb.Append(part.Substring(1));
+                    if (length > 1)
+                    {
+                        sb.Append(c);
+                    }
+                    else if (length == 0)
+                    {
+                        last = c;
+                    }
+                    else
+                    {
+                        sb.Append(char.ToUpperInvariant(last));
+                        sb.Append(c);
+
+                        last = NullChar;
+                    }
+
+                    length++;
                 }
             }
 
+            if (last != NullChar)
+            {
+                sb.Append(char.ToUpperInvariant(last));
+            }
+
             return sb.ToString();
         }
 
         public static string ToKebabCase(this string value)
         {
+            if (value.Length == 0)
+            {
+                return string.Empty;
+            }
+
             var sb = new StringBuilder();
 
-            foreach (var part in value.Split(new[] { '-', '_', ' ' }, StringSplitOptions.RemoveEmptyEntries))
+            var length = 0;
+
+            for (var i = 0; i < value.Length; i++)
             {
-                if (sb.Length > 0)
+                var c = value[i];
+
+                if (c == '-' || c == '_' || c == ' ')
                 {
-                    sb.Append("-");
+                    length = 0;
                 }
+                else
+                {
+                    if (length > 0)
+                    {
+                        sb.Append(char.ToLowerInvariant(c));
+                    }
+                    else
+                    {
+                        if (sb.Length > 0)
+                        {
+                            sb.Append('-');
+                        }
+
+                        sb.Append(char.ToLowerInvariant(c));
+                    }
 
-                sb.Append(part.ToLower());
+                    length++;
+                }
             }
 
             return sb.ToString();
@@ -362,16 +424,80 @@ namespace Squidex.Infrastructure
 
         public static string ToCamelCase(this string value)
         {
-            value = value.ToPascalCase();
+            if (value.Length == 0)
+            {
+                return string.Empty;
+            }
 
-            if (value.Length < 2)
+            var sb = new StringBuilder();
+
+            var last = NullChar;
+            var length = 0;
+
+            for (var i = 0; i < value.Length; i++)
             {
-                return value.ToLower();
+                var c = value[i];
+
+                if (c == '-' || c == '_' || c == ' ')
+                {
+                    if (last != NullChar)
+                    {
+                        if (sb.Length > 0)
+                        {
+                            sb.Append(char.ToUpperInvariant(last));
+                        }
+                        else
+                        {
+                            sb.Append(char.ToLowerInvariant(last));
+                        }
+                    }
+
+                    last = NullChar;
+                    length = 0;
+                }
+                else
+                {
+                    if (length > 1)
+                    {
+                        sb.Append(c);
+                    }
+                    else if (length == 0)
+                    {
+                        last = c;
+                    }
+                    else
+                    {
+                        if (sb.Length > 0)
+                        {
+                            sb.Append(char.ToUpperInvariant(last));
+                        }
+                        else
+                        {
+                            sb.Append(char.ToLowerInvariant(last));
+                        }
+
+                        sb.Append(c);
+
+                        last = NullChar;
+                    }
+
+                    length++;
+                }
             }
-            else
+
+            if (last != NullChar)
             {
-                return char.ToLower(value[0]) + value.Substring(1);
+                if (sb.Length > 0)
+                {
+                    sb.Append(char.ToUpperInvariant(last));
+                }
+                else
+                {
+                    sb.Append(char.ToLowerInvariant(last));
+                }
             }
+
+            return sb.ToString();
         }
 
         public static string Slugify(this string value, ISet<char> preserveHash = null, bool singleCharDiactric = false, char separator = '-')
diff --git a/src/Squidex.Infrastructure/ValidationError.cs b/src/Squidex.Infrastructure/ValidationError.cs
index 2ae3c5de4..5d0027514 100644
--- a/src/Squidex.Infrastructure/ValidationError.cs
+++ b/src/Squidex.Infrastructure/ValidationError.cs
@@ -14,7 +14,6 @@ namespace Squidex.Infrastructure
     [Serializable]
     public sealed class ValidationError
     {
-        private static readonly string[] FallbackProperties = Array.Empty<string>();
         private readonly string message;
         private readonly string[] propertyNames;
 
@@ -34,7 +33,7 @@ namespace Squidex.Infrastructure
 
             this.message = message;
 
-            this.propertyNames = propertyNames ?? FallbackProperties;
+            this.propertyNames = propertyNames ?? Array.Empty<string>();
         }
 
         public ValidationError WithPrefix(string prefix)
diff --git a/src/Squidex/Areas/Api/Controllers/Rules/Models/Triggers/ContentChangedTriggerDto.cs b/src/Squidex/Areas/Api/Controllers/Rules/Models/Triggers/ContentChangedTriggerDto.cs
index 9aa436d5f..219d42c1a 100644
--- a/src/Squidex/Areas/Api/Controllers/Rules/Models/Triggers/ContentChangedTriggerDto.cs
+++ b/src/Squidex/Areas/Api/Controllers/Rules/Models/Triggers/ContentChangedTriggerDto.cs
@@ -5,13 +5,12 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.ComponentModel.DataAnnotations;
 using System.Linq;
 using NJsonSchema.Annotations;
 using Squidex.Domain.Apps.Core.Rules;
 using Squidex.Domain.Apps.Core.Rules.Triggers;
+using Squidex.Infrastructure.Collections;
 using Squidex.Infrastructure.Reflection;
 
 namespace Squidex.Areas.Api.Controllers.Rules.Models.Triggers
@@ -32,7 +31,7 @@ namespace Squidex.Areas.Api.Controllers.Rules.Models.Triggers
 
         public override RuleTrigger ToTrigger()
         {
-            var schemas = Schemas.Select(x => SimpleMapper.Map(x, new ContentChangedTriggerSchema())).ToImmutableList();
+            var schemas = Schemas.Select(x => SimpleMapper.Map(x, new ContentChangedTriggerSchema())).ToReadOnlyCollection();
 
             return new ContentChangedTrigger { HandleAll = HandleAll, Schemas = schemas };
         }
diff --git a/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/AssetsFieldPropertiesDto.cs b/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/AssetsFieldPropertiesDto.cs
index e3ce42d5c..f3bdb67bd 100644
--- a/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/AssetsFieldPropertiesDto.cs
+++ b/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/AssetsFieldPropertiesDto.cs
@@ -5,9 +5,9 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
 using NJsonSchema.Annotations;
 using Squidex.Domain.Apps.Core.Schemas;
+using Squidex.Infrastructure.Collections;
 using Squidex.Infrastructure.Reflection;
 
 namespace Squidex.Areas.Api.Controllers.Schemas.Models.Fields
@@ -81,7 +81,7 @@ namespace Squidex.Areas.Api.Controllers.Schemas.Models.Fields
 
             if (AllowedExtensions != null)
             {
-                result.AllowedExtensions = ImmutableList.Create(AllowedExtensions);
+                result.AllowedExtensions = ReadOnlyCollection.Create(AllowedExtensions);
             }
 
             return result;
diff --git a/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/NumberFieldPropertiesDto.cs b/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/NumberFieldPropertiesDto.cs
index 3a255891c..4a7861b04 100644
--- a/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/NumberFieldPropertiesDto.cs
+++ b/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/NumberFieldPropertiesDto.cs
@@ -5,11 +5,11 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Converters;
 using NJsonSchema.Annotations;
 using Squidex.Domain.Apps.Core.Schemas;
+using Squidex.Infrastructure.Collections;
 using Squidex.Infrastructure.Reflection;
 
 namespace Squidex.Areas.Api.Controllers.Schemas.Models.Fields
@@ -54,7 +54,7 @@ namespace Squidex.Areas.Api.Controllers.Schemas.Models.Fields
 
             if (AllowedValues != null)
             {
-                result.AllowedValues = ImmutableList.Create(AllowedValues);
+                result.AllowedValues = ReadOnlyCollection.Create(AllowedValues);
             }
 
             return result;
diff --git a/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/StringFieldPropertiesDto.cs b/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/StringFieldPropertiesDto.cs
index 4451846ca..0722fec99 100644
--- a/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/StringFieldPropertiesDto.cs
+++ b/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/StringFieldPropertiesDto.cs
@@ -5,11 +5,11 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Converters;
 using NJsonSchema.Annotations;
 using Squidex.Domain.Apps.Core.Schemas;
+using Squidex.Infrastructure.Collections;
 using Squidex.Infrastructure.Reflection;
 
 namespace Squidex.Areas.Api.Controllers.Schemas.Models.Fields
@@ -64,7 +64,7 @@ namespace Squidex.Areas.Api.Controllers.Schemas.Models.Fields
 
             if (AllowedValues != null)
             {
-                result.AllowedValues = ImmutableList.Create(AllowedValues);
+                result.AllowedValues = ReadOnlyCollection.Create(AllowedValues);
             }
 
             return result;
diff --git a/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/TagsFieldPropertiesDto.cs b/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/TagsFieldPropertiesDto.cs
index 147309749..3a7727107 100644
--- a/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/TagsFieldPropertiesDto.cs
+++ b/src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/TagsFieldPropertiesDto.cs
@@ -5,11 +5,11 @@
 //  All rights reserved. Licensed under the MIT license.
 // ==========================================================================
 
-using System.Collections.Immutable;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Converters;
 using NJsonSchema.Annotations;
 using Squidex.Domain.Apps.Core.Schemas;
+using Squidex.Infrastructure.Collections;
 using Squidex.Infrastructure.Reflection;
 
 namespace Squidex.Areas.Api.Controllers.Schemas.Models.Fields
@@ -44,7 +44,7 @@ namespace Squidex.Areas.Api.Controllers.Schemas.Models.Fields
 
             if (AllowedValues != null)
             {
-                result.AllowedValues = ImmutableList.Create(AllowedValues);
+                result.AllowedValues = ReadOnlyCollection.Create(AllowedValues);
             }
 
             return result;
diff --git a/src/Squidex/Config/Domain/SerializationServices.cs b/src/Squidex/Config/Domain/SerializationServices.cs
index c52abca55..be0d316e6 100644
--- a/src/Squidex/Config/Domain/SerializationServices.cs
+++ b/src/Squidex/Config/Domain/SerializationServices.cs
@@ -59,7 +59,7 @@ namespace Squidex.Config.Domain
                 new RefTokenConverter(),
                 new RolesConverter(),
                 new RuleConverter(),
-                new SchemaConverter(FieldRegistry),
+                new SchemaConverter(),
                 new StringEnumConverter());
 
             settings.NullValueHandling = NullValueHandling.Ignore;
diff --git a/tests/Squidex.Domain.Apps.Core.Tests/Model/Apps/AppClientsTests.cs b/tests/Squidex.Domain.Apps.Core.Tests/Model/Apps/AppClientsTests.cs
index 4a97de100..9f95ac4b2 100644
--- a/tests/Squidex.Domain.Apps.Core.Tests/Model/Apps/AppClientsTests.cs
+++ b/tests/Squidex.Domain.Apps.Core.Tests/Model/Apps/AppClientsTests.cs
@@ -35,13 +35,21 @@ namespace Squidex.Domain.Apps.Core.Model.Apps
         }
 
         [Fact]
-        public void Should_throw_exception_if_assigning_clients_with_same_id()
+        public void Should_throw_exception_if_assigning_client_with_same_id()
         {
             var clients_1 = clients_0.Add("2", "my-secret");
 
             Assert.Throws<ArgumentException>(() => clients_1.Add("2", "my-secret"));
         }
 
+        [Fact]
+        public void Should_throw_exception_if_assigning_client_object_with_same_id()
+        {
+            var clients_1 = clients_0.Add("2", "my-secret");
+
+            Assert.Throws<ArgumentException>(() => clients_1.Add("2", new AppClient("my-name", "my-secret", "my-role")));
+        }
+
         [Fact]
         public void Should_rename_client()
         {
diff --git a/tests/Squidex.Domain.Apps.Core.Tests/Operations/HandleRules/Triggers/ContentChangedTriggerTests.cs b/tests/Squidex.Domain.Apps.Core.Tests/Operations/HandleRules/Triggers/ContentChangedTriggerTests.cs
index 6989b814c..f24fdf033 100644
--- a/tests/Squidex.Domain.Apps.Core.Tests/Operations/HandleRules/Triggers/ContentChangedTriggerTests.cs
+++ b/tests/Squidex.Domain.Apps.Core.Tests/Operations/HandleRules/Triggers/ContentChangedTriggerTests.cs
@@ -7,7 +7,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using Squidex.Domain.Apps.Core.Contents;
 using Squidex.Domain.Apps.Core.HandleRules;
 using Squidex.Domain.Apps.Core.HandleRules.Triggers;
@@ -17,6 +16,7 @@ using Squidex.Domain.Apps.Events.Contents;
 using Squidex.Domain.Apps.Events.Rules;
 using Squidex.Domain.Apps.Events.Schemas;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 using Squidex.Infrastructure.EventSourcing;
 using Xunit;
 
@@ -85,7 +85,7 @@ namespace Squidex.Domain.Apps.Core.Operations.HandleRules.Triggers
         {
             var trigger = new ContentChangedTrigger
             {
-                Schemas = ImmutableList.Create(
+                Schemas = ReadOnlyCollection.Create(
                     new ContentChangedTriggerSchema
                     {
                         SendCreate = sendCreate == 1,
diff --git a/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/AssetsFieldTests.cs b/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/AssetsFieldTests.cs
index c82f95373..36aa3c0e0 100644
--- a/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/AssetsFieldTests.cs
+++ b/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/AssetsFieldTests.cs
@@ -7,13 +7,13 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Linq;
 using System.Threading.Tasks;
 using FluentAssertions;
 using Newtonsoft.Json.Linq;
 using Squidex.Domain.Apps.Core.Schemas;
 using Squidex.Domain.Apps.Core.ValidateContent;
+using Squidex.Infrastructure.Collections;
 using Xunit;
 
 namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
@@ -251,7 +251,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_error_if_image_has_invalid_extension()
         {
-            var sut = Field(new AssetsFieldProperties { AllowedExtensions = ImmutableList.Create("mp4") });
+            var sut = Field(new AssetsFieldProperties { AllowedExtensions = ReadOnlyCollection.Create("mp4") });
 
             await sut.ValidateAsync(CreateValue(document.AssetId, image.AssetId), errors, ctx);
 
diff --git a/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/NumberFieldTests.cs b/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/NumberFieldTests.cs
index eac18056e..d236198f9 100644
--- a/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/NumberFieldTests.cs
+++ b/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/NumberFieldTests.cs
@@ -6,11 +6,11 @@
 // ==========================================================================
 
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Threading.Tasks;
 using FluentAssertions;
 using Newtonsoft.Json.Linq;
 using Squidex.Domain.Apps.Core.Schemas;
+using Squidex.Infrastructure.Collections;
 using Xunit;
 
 namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
@@ -73,7 +73,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_number_is_not_allowed()
         {
-            var sut = Field(new NumberFieldProperties { AllowedValues = ImmutableList.Create(10d) });
+            var sut = Field(new NumberFieldProperties { AllowedValues = ReadOnlyCollection.Create(10d) });
 
             await sut.ValidateAsync(CreateValue(20), errors);
 
diff --git a/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/StringFieldTests.cs b/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/StringFieldTests.cs
index 87dd5f4f6..46f9a17de 100644
--- a/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/StringFieldTests.cs
+++ b/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/StringFieldTests.cs
@@ -6,11 +6,11 @@
 // ==========================================================================
 
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Threading.Tasks;
 using FluentAssertions;
 using Newtonsoft.Json.Linq;
 using Squidex.Domain.Apps.Core.Schemas;
+using Squidex.Infrastructure.Collections;
 using Xunit;
 
 namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
@@ -73,7 +73,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_string_not_allowed()
         {
-            var sut = Field(new StringFieldProperties { AllowedValues = ImmutableList.Create("Foo") });
+            var sut = Field(new StringFieldProperties { AllowedValues = ReadOnlyCollection.Create("Foo") });
 
             await sut.ValidateAsync(CreateValue("Bar"), errors);
 
diff --git a/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/TagsFieldTests.cs b/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/TagsFieldTests.cs
index e8ec0795c..3b2a4d3c2 100644
--- a/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/TagsFieldTests.cs
+++ b/tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/TagsFieldTests.cs
@@ -6,12 +6,12 @@
 // ==========================================================================
 
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Linq;
 using System.Threading.Tasks;
 using FluentAssertions;
 using Newtonsoft.Json.Linq;
 using Squidex.Domain.Apps.Core.Schemas;
+using Squidex.Infrastructure.Collections;
 using Xunit;
 
 namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
@@ -106,7 +106,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_contains_an_not_allowed_values()
         {
-            var sut = Field(new TagsFieldProperties { AllowedValues = ImmutableList.Create("tag-2", "tag-3") });
+            var sut = Field(new TagsFieldProperties { AllowedValues = ReadOnlyCollection.Create("tag-2", "tag-3") });
 
             await sut.ValidateAsync(CreateValue("tag-1", "tag-2", null), errors);
 
diff --git a/tests/Squidex.Domain.Apps.Core.Tests/TestData.cs b/tests/Squidex.Domain.Apps.Core.Tests/TestData.cs
index 354dfa971..6b10c3145 100644
--- a/tests/Squidex.Domain.Apps.Core.Tests/TestData.cs
+++ b/tests/Squidex.Domain.Apps.Core.Tests/TestData.cs
@@ -6,7 +6,6 @@
 // ==========================================================================
 
 using System;
-using System.Collections.Immutable;
 using System.Linq;
 using System.Reflection;
 using Newtonsoft.Json;
@@ -16,6 +15,7 @@ using Squidex.Domain.Apps.Core.Rules.Json;
 using Squidex.Domain.Apps.Core.Schemas;
 using Squidex.Domain.Apps.Core.Schemas.Json;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 using Squidex.Infrastructure.Json;
 using Xunit;
 
@@ -44,7 +44,7 @@ namespace Squidex.Domain.Apps.Core
                     new RefTokenConverter(),
                     new RolesConverter(),
                     new RuleConverter(),
-                    new SchemaConverter(new FieldRegistry(typeNameRegistry)),
+                    new SchemaConverter(),
                     new StringEnumConverter()),
 
                 TypeNameHandling = TypeNameHandling.Auto
@@ -85,7 +85,7 @@ namespace Squidex.Domain.Apps.Core
                 .AddReferences(109, "root-references", Partitioning.Invariant,
                     new ReferencesFieldProperties())
                 .AddString(110, "root-string1", Partitioning.Invariant,
-                    new StringFieldProperties { Label = "My String1", IsRequired = true, AllowedValues = ImmutableList.Create("a", "b") })
+                    new StringFieldProperties { Label = "My String1", IsRequired = true, AllowedValues = ReadOnlyCollection.Create("a", "b") })
                 .AddString(111, "root-string2", Partitioning.Invariant,
                     new StringFieldProperties { Hints = "My String1" })
                 .AddTags(112, "root-tags", Partitioning.Language,
diff --git a/tests/Squidex.Domain.Apps.Entities.Tests/Contents/MongoDb/MongoDbQueryTests.cs b/tests/Squidex.Domain.Apps.Entities.Tests/Contents/MongoDb/MongoDbQueryTests.cs
index 9307fab0f..1b2b8c81e 100644
--- a/tests/Squidex.Domain.Apps.Entities.Tests/Contents/MongoDb/MongoDbQueryTests.cs
+++ b/tests/Squidex.Domain.Apps.Entities.Tests/Contents/MongoDb/MongoDbQueryTests.cs
@@ -6,7 +6,6 @@
 // ==========================================================================
 
 using System;
-using System.Collections.Immutable;
 using System.Linq;
 using FakeItEasy;
 using MongoDB.Bson.Serialization;
@@ -20,6 +19,7 @@ using Squidex.Domain.Apps.Entities.MongoDb.Contents;
 using Squidex.Domain.Apps.Entities.MongoDb.Contents.Visitors;
 using Squidex.Domain.Apps.Entities.Schemas;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 using Squidex.Infrastructure.MongoDb;
 using Squidex.Infrastructure.MongoDb.Queries;
 using Squidex.Infrastructure.Queries;
@@ -46,7 +46,7 @@ namespace Squidex.Domain.Apps.Entities.Contents.MongoDb
             schemaDef =
                 new Schema("user")
                     .AddString(1, "firstName", Partitioning.Language,
-                        new StringFieldProperties { Label = "FirstName", IsRequired = true, AllowedValues = ImmutableList.Create("1", "2") })
+                        new StringFieldProperties { Label = "FirstName", IsRequired = true, AllowedValues = ReadOnlyCollection.Create("1", "2") })
                     .AddString(2, "lastName", Partitioning.Language,
                         new StringFieldProperties { Hints = "Last Name", Editor = StringFieldEditor.Input })
                     .AddBoolean(3, "isAdmin", Partitioning.Invariant,
diff --git a/tests/Squidex.Domain.Apps.Entities.Tests/Rules/Guards/GuardRuleTests.cs b/tests/Squidex.Domain.Apps.Entities.Tests/Rules/Guards/GuardRuleTests.cs
index 8851bdc79..837387d2a 100644
--- a/tests/Squidex.Domain.Apps.Entities.Tests/Rules/Guards/GuardRuleTests.cs
+++ b/tests/Squidex.Domain.Apps.Entities.Tests/Rules/Guards/GuardRuleTests.cs
@@ -6,7 +6,6 @@
 // ==========================================================================
 
 using System;
-using System.Collections.Immutable;
 using System.Threading.Tasks;
 using FakeItEasy;
 using Squidex.Domain.Apps.Core.Rules;
@@ -15,6 +14,7 @@ using Squidex.Domain.Apps.Entities.Rules.Commands;
 using Squidex.Domain.Apps.Entities.Schemas;
 using Squidex.Domain.Apps.Entities.TestHelpers;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 using Xunit;
 
 #pragma warning disable SA1310 // Field names must not contain underscore
@@ -62,7 +62,7 @@ namespace Squidex.Domain.Apps.Entities.Rules.Guards
             {
                 Trigger = new ContentChangedTrigger
                 {
-                    Schemas = ImmutableList<ContentChangedTriggerSchema>.Empty
+                    Schemas = ReadOnlyCollection.Empty<ContentChangedTriggerSchema>()
                 },
                 Action = null
             });
@@ -78,7 +78,7 @@ namespace Squidex.Domain.Apps.Entities.Rules.Guards
             {
                 Trigger = new ContentChangedTrigger
                 {
-                    Schemas = ImmutableList<ContentChangedTriggerSchema>.Empty
+                    Schemas = ReadOnlyCollection.Empty<ContentChangedTriggerSchema>()
                 },
                 Action = new TestAction
                 {
@@ -105,7 +105,7 @@ namespace Squidex.Domain.Apps.Entities.Rules.Guards
             {
                 Trigger = new ContentChangedTrigger
                 {
-                    Schemas = ImmutableList<ContentChangedTriggerSchema>.Empty
+                    Schemas = ReadOnlyCollection.Empty<ContentChangedTriggerSchema>()
                 },
                 Action = new TestAction
                 {
diff --git a/tests/Squidex.Domain.Apps.Entities.Tests/Rules/Guards/Triggers/ContentChangedTriggerTests.cs b/tests/Squidex.Domain.Apps.Entities.Tests/Rules/Guards/Triggers/ContentChangedTriggerTests.cs
index cee1ddb81..4e1f6af25 100644
--- a/tests/Squidex.Domain.Apps.Entities.Tests/Rules/Guards/Triggers/ContentChangedTriggerTests.cs
+++ b/tests/Squidex.Domain.Apps.Entities.Tests/Rules/Guards/Triggers/ContentChangedTriggerTests.cs
@@ -6,11 +6,11 @@
 // ==========================================================================
 
 using System;
-using System.Collections.Immutable;
 using System.Threading.Tasks;
 using FakeItEasy;
 using Squidex.Domain.Apps.Core.Rules.Triggers;
 using Squidex.Domain.Apps.Entities.Schemas;
+using Squidex.Infrastructure.Collections;
 using Xunit;
 
 namespace Squidex.Domain.Apps.Entities.Rules.Guards.Triggers
@@ -28,7 +28,7 @@ namespace Squidex.Domain.Apps.Entities.Rules.Guards.Triggers
 
             var trigger = new ContentChangedTrigger
             {
-                Schemas = ImmutableList.Create(
+                Schemas = ReadOnlyCollection.Create(
                     new ContentChangedTriggerSchema()
                 )
             };
@@ -53,7 +53,7 @@ namespace Squidex.Domain.Apps.Entities.Rules.Guards.Triggers
         {
             var trigger = new ContentChangedTrigger
             {
-                Schemas = ImmutableList<ContentChangedTriggerSchema>.Empty
+                Schemas = ReadOnlyCollection.Empty<ContentChangedTriggerSchema>()
             };
 
             var errors = await RuleTriggerValidator.ValidateAsync(appId, trigger, appProvider);
@@ -69,7 +69,7 @@ namespace Squidex.Domain.Apps.Entities.Rules.Guards.Triggers
 
             var trigger = new ContentChangedTrigger
             {
-                Schemas = ImmutableList.Create(
+                Schemas = ReadOnlyCollection.Create(
                     new ContentChangedTriggerSchema()
                 )
             };
diff --git a/tests/Squidex.Domain.Apps.Entities.Tests/Rules/RuleGrainTests.cs b/tests/Squidex.Domain.Apps.Entities.Tests/Rules/RuleGrainTests.cs
index 80dd4b4d2..eae59aba9 100644
--- a/tests/Squidex.Domain.Apps.Entities.Tests/Rules/RuleGrainTests.cs
+++ b/tests/Squidex.Domain.Apps.Entities.Tests/Rules/RuleGrainTests.cs
@@ -6,7 +6,6 @@
 // ==========================================================================
 
 using System;
-using System.Collections.Immutable;
 using System.Threading.Tasks;
 using FakeItEasy;
 using Squidex.Domain.Apps.Core.Rules;
@@ -16,6 +15,7 @@ using Squidex.Domain.Apps.Entities.Rules.State;
 using Squidex.Domain.Apps.Entities.TestHelpers;
 using Squidex.Domain.Apps.Events.Rules;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 using Squidex.Infrastructure.Commands;
 using Squidex.Infrastructure.Log;
 using Xunit;
@@ -191,7 +191,7 @@ namespace Squidex.Domain.Apps.Entities.Rules
         {
             var newTrigger = new ContentChangedTrigger
             {
-                Schemas = ImmutableList<ContentChangedTriggerSchema>.Empty
+                Schemas = ReadOnlyCollection.Empty<ContentChangedTriggerSchema>()
             };
 
             var newAction = new TestAction
@@ -206,7 +206,7 @@ namespace Squidex.Domain.Apps.Entities.Rules
         {
             var newTrigger = new ContentChangedTrigger
             {
-                Schemas = ImmutableList<ContentChangedTriggerSchema>.Empty
+                Schemas = ReadOnlyCollection.Empty<ContentChangedTriggerSchema>()
             };
 
             var newAction = new TestAction
diff --git a/tests/Squidex.Domain.Apps.Entities.Tests/Schemas/Guards/FieldProperties/NumberFieldPropertiesTests.cs b/tests/Squidex.Domain.Apps.Entities.Tests/Schemas/Guards/FieldProperties/NumberFieldPropertiesTests.cs
index f9d1c303c..a017a3f51 100644
--- a/tests/Squidex.Domain.Apps.Entities.Tests/Schemas/Guards/FieldProperties/NumberFieldPropertiesTests.cs
+++ b/tests/Squidex.Domain.Apps.Entities.Tests/Schemas/Guards/FieldProperties/NumberFieldPropertiesTests.cs
@@ -6,11 +6,11 @@
 // ==========================================================================
 
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Linq;
 using FluentAssertions;
 using Squidex.Domain.Apps.Core.Schemas;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 using Xunit;
 
 namespace Squidex.Domain.Apps.Entities.Schemas.Guards.FieldProperties
@@ -77,7 +77,7 @@ namespace Squidex.Domain.Apps.Entities.Schemas.Guards.FieldProperties
         [Fact]
         public void Should_add_error_if_allowed_values_and_max_value_is_specified()
         {
-            var sut = new NumberFieldProperties { MaxValue = 10, AllowedValues = ImmutableList.Create(4d) };
+            var sut = new NumberFieldProperties { MaxValue = 10, AllowedValues = ReadOnlyCollection.Create(4d) };
 
             var errors = FieldPropertiesValidator.Validate(sut).ToList();
 
@@ -91,7 +91,7 @@ namespace Squidex.Domain.Apps.Entities.Schemas.Guards.FieldProperties
         [Fact]
         public void Should_add_error_if_allowed_values_and_min_value_is_specified()
         {
-            var sut = new NumberFieldProperties { MinValue = 10, AllowedValues = ImmutableList.Create(4d) };
+            var sut = new NumberFieldProperties { MinValue = 10, AllowedValues = ReadOnlyCollection.Create(4d) };
 
             var errors = FieldPropertiesValidator.Validate(sut).ToList();
 
@@ -135,7 +135,7 @@ namespace Squidex.Domain.Apps.Entities.Schemas.Guards.FieldProperties
         [InlineData(NumberFieldEditor.Stars)]
         public void Should_add_error_if_inline_editing_is_not_allowed_for_editor(NumberFieldEditor editor)
         {
-            var sut = new NumberFieldProperties { InlineEditable = true, Editor = editor, AllowedValues = ImmutableList.Create(1.0) };
+            var sut = new NumberFieldProperties { InlineEditable = true, Editor = editor, AllowedValues = ReadOnlyCollection.Create(1.0) };
 
             var errors = FieldPropertiesValidator.Validate(sut).ToList();
 
@@ -151,7 +151,7 @@ namespace Squidex.Domain.Apps.Entities.Schemas.Guards.FieldProperties
         [InlineData(NumberFieldEditor.Dropdown)]
         public void Should_not_add_error_if_inline_editing_is_allowed_for_editor(NumberFieldEditor editor)
         {
-            var sut = new NumberFieldProperties { InlineEditable = true, Editor = editor, AllowedValues = ImmutableList.Create(1.0) };
+            var sut = new NumberFieldProperties { InlineEditable = true, Editor = editor, AllowedValues = ReadOnlyCollection.Create(1.0) };
 
             var errors = FieldPropertiesValidator.Validate(sut).ToList();
 
diff --git a/tests/Squidex.Domain.Apps.Entities.Tests/Schemas/Guards/FieldProperties/StringFieldPropertiesTests.cs b/tests/Squidex.Domain.Apps.Entities.Tests/Schemas/Guards/FieldProperties/StringFieldPropertiesTests.cs
index ed5382b4e..ad6faed6a 100644
--- a/tests/Squidex.Domain.Apps.Entities.Tests/Schemas/Guards/FieldProperties/StringFieldPropertiesTests.cs
+++ b/tests/Squidex.Domain.Apps.Entities.Tests/Schemas/Guards/FieldProperties/StringFieldPropertiesTests.cs
@@ -6,11 +6,11 @@
 // ==========================================================================
 
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using System.Linq;
 using FluentAssertions;
 using Squidex.Domain.Apps.Core.Schemas;
 using Squidex.Infrastructure;
+using Squidex.Infrastructure.Collections;
 using Xunit;
 
 namespace Squidex.Domain.Apps.Entities.Schemas.Guards.FieldProperties
@@ -34,7 +34,7 @@ namespace Squidex.Domain.Apps.Entities.Schemas.Guards.FieldProperties
         [Fact]
         public void Should_add_error_if_allowed_values_and_max_value_is_specified()
         {
-            var sut = new StringFieldProperties { MinLength = 10, AllowedValues = ImmutableList.Create("4") };
+            var sut = new StringFieldProperties { MinLength = 10, AllowedValues = ReadOnlyCollection.Create("4") };
 
             var errors = FieldPropertiesValidator.Validate(sut).ToList();
 
@@ -48,7 +48,7 @@ namespace Squidex.Domain.Apps.Entities.Schemas.Guards.FieldProperties
         [Fact]
         public void Should_add_error_if_allowed_values_and_min_value_is_specified()
         {
-            var sut = new StringFieldProperties { MaxLength = 10, AllowedValues = ImmutableList.Create("4") };
+            var sut = new StringFieldProperties { MaxLength = 10, AllowedValues = ReadOnlyCollection.Create("4") };
 
             var errors = FieldPropertiesValidator.Validate(sut).ToList();
 
@@ -108,7 +108,7 @@ namespace Squidex.Domain.Apps.Entities.Schemas.Guards.FieldProperties
         [InlineData(StringFieldEditor.TextArea)]
         public void Should_add_error_if_inline_editing_is_not_allowed_for_editor(StringFieldEditor editor)
         {
-            var sut = new StringFieldProperties { InlineEditable = true, Editor = editor, AllowedValues = ImmutableList.Create("Value") };
+            var sut = new StringFieldProperties { InlineEditable = true, Editor = editor, AllowedValues = ReadOnlyCollection.Create("Value") };
 
             var errors = FieldPropertiesValidator.Validate(sut).ToList();
 
@@ -125,7 +125,7 @@ namespace Squidex.Domain.Apps.Entities.Schemas.Guards.FieldProperties
         [InlineData(StringFieldEditor.Slug)]
         public void Should_not_add_error_if_inline_editing_is_allowed_for_editor(StringFieldEditor editor)
         {
-            var sut = new StringFieldProperties { InlineEditable = true, Editor = editor, AllowedValues = ImmutableList.Create("Value") };
+            var sut = new StringFieldProperties { InlineEditable = true, Editor = editor, AllowedValues = ReadOnlyCollection.Create("Value") };
 
             var errors = FieldPropertiesValidator.Validate(sut).ToList();
 
diff --git a/tests/Squidex.Infrastructure.Tests/CollectionExtensionsTests.cs b/tests/Squidex.Infrastructure.Tests/CollectionExtensionsTests.cs
index d540ff429..8a2851e74 100644
--- a/tests/Squidex.Infrastructure.Tests/CollectionExtensionsTests.cs
+++ b/tests/Squidex.Infrastructure.Tests/CollectionExtensionsTests.cs
@@ -6,7 +6,6 @@
 // ==========================================================================
 
 using System.Collections.Generic;
-using System.Collections.Immutable;
 using Xunit;
 
 namespace Squidex.Infrastructure
@@ -275,35 +274,5 @@ namespace Squidex.Infrastructure
 
             Assert.Equal(source, target);
         }
-
-        [Fact]
-        public void Should_return_same_dictionary_if_item_to_replace_not_found()
-        {
-            var dict_0 = ImmutableDictionary<int, int>.Empty;
-            var dict_1 = dict_0.SetItem(1, x => x);
-
-            Assert.Same(dict_0, dict_1);
-        }
-
-        [Fact]
-        public void Should_return_same_dictionary_if_replaced_item_is_same()
-        {
-            var dict_0 = ImmutableDictionary<int, int>.Empty;
-            var dict_1 = dict_0.SetItem(1, 1);
-            var dict_2 = dict_1.SetItem(1, x => x);
-
-            Assert.Same(dict_1, dict_2);
-        }
-
-        [Fact]
-        public void Should_return_new_dictionary_if_updated_item_is_different()
-        {
-            var dict_0 = ImmutableDictionary<int, int>.Empty;
-            var dict_1 = dict_0.SetItem(2, 2);
-            var dict_2 = dict_1.SetItem(2, x => 2 * x);
-
-            Assert.NotSame(dict_1, dict_2);
-            Assert.Equal(4, dict_2[2]);
-        }
     }
 }
\ No newline at end of file