diff --git a/osu.Game.Rulesets.Karaoke/Beatmaps/Formats/KaraokeLegacyBeatmapDecoder.cs b/osu.Game.Rulesets.Karaoke/Beatmaps/Formats/KaraokeLegacyBeatmapDecoder.cs
index 9bad8a457..adf8a1355 100644
--- a/osu.Game.Rulesets.Karaoke/Beatmaps/Formats/KaraokeLegacyBeatmapDecoder.cs
+++ b/osu.Game.Rulesets.Karaoke/Beatmaps/Formats/KaraokeLegacyBeatmapDecoder.cs
@@ -230,7 +230,7 @@ private void processTranslate(Beatmap beatmap, IEnumerable<string> translateLine
             var translations = translateLines.Select(translate => new
             {
                 key = translate.Split('=').FirstOrDefault()?.Split('[').LastOrDefault()?.Split(']').FirstOrDefault(),
-                value = translate.Split('=').LastOrDefault()
+                value = translate.Split('=').LastOrDefault() ?? string.Empty
             }).GroupBy(x => x.key, y => y.value).ToList();
 
             foreach (var translation in translations)
diff --git a/osu.Game.Rulesets.Karaoke/Beatmaps/Formats/KaraokeLegacyBeatmapEncoder.cs b/osu.Game.Rulesets.Karaoke/Beatmaps/Formats/KaraokeLegacyBeatmapEncoder.cs
index 7c75263c2..4123dda28 100644
--- a/osu.Game.Rulesets.Karaoke/Beatmaps/Formats/KaraokeLegacyBeatmapEncoder.cs
+++ b/osu.Game.Rulesets.Karaoke/Beatmaps/Formats/KaraokeLegacyBeatmapEncoder.cs
@@ -32,7 +32,7 @@ private IEnumerable<string> encodeNote(Beatmap output)
             {
                 var lyric = g.Key;
                 if (lyric == null)
-                    throw new NullReferenceException();
+                    throw new ArgumentNullException();
 
                 // Get note group
                 var noteGroup = g.ToList().GroupBy(n => n.ReferenceTimeTagIndex);
@@ -75,7 +75,7 @@ private IEnumerable<string> encodeTranslate(Beatmap output)
             {
                 foreach (var lyric in lyrics)
                 {
-                    string translateString = lyric.Translates.TryGetValue(translate, out string value) ? value : string.Empty;
+                    string translateString = lyric.Translates.TryGetValue(translate, out string? value) ? value : string.Empty;
                     yield return $"@tr[{translate.Name}]={translateString}";
                 }
             }
diff --git a/osu.Game.Rulesets.Karaoke/Beatmaps/KaraokeBeatmapResourcesProvider.cs b/osu.Game.Rulesets.Karaoke/Beatmaps/KaraokeBeatmapResourcesProvider.cs
index 35fcd2a6e..508e87351 100644
--- a/osu.Game.Rulesets.Karaoke/Beatmaps/KaraokeBeatmapResourcesProvider.cs
+++ b/osu.Game.Rulesets.Karaoke/Beatmaps/KaraokeBeatmapResourcesProvider.cs
@@ -45,7 +45,7 @@ private IBeatmapResourceProvider getBeatmapResourceProvider()
             // todo : use better way to get the resource provider.
             var prop = typeof(BeatmapManager).GetField("workingBeatmapCache", BindingFlags.Instance | BindingFlags.NonPublic);
             if (prop == null)
-                throw new NullReferenceException();
+                throw new ArgumentNullException();
 
             return prop.GetValue(beatmapManager) as WorkingBeatmapCache;
         }
diff --git a/osu.Game.Rulesets.Karaoke/Beatmaps/Metadatas/Page.cs b/osu.Game.Rulesets.Karaoke/Beatmaps/Metadatas/Page.cs
index dbcbb53dd..5682820c0 100644
--- a/osu.Game.Rulesets.Karaoke/Beatmaps/Metadatas/Page.cs
+++ b/osu.Game.Rulesets.Karaoke/Beatmaps/Metadatas/Page.cs
@@ -27,7 +27,7 @@ public Page DeepClone()
         };
     }
 
-    public int CompareTo(Page other) => Time.CompareTo(other.Time);
+    public int CompareTo(Page? other) => Time.CompareTo(other?.Time);
 
     public override int GetHashCode() => Time.GetHashCode();
 }
diff --git a/osu.Game.Rulesets.Karaoke/Beatmaps/Metadatas/PageInfo.cs b/osu.Game.Rulesets.Karaoke/Beatmaps/Metadatas/PageInfo.cs
index 3456e5ab9..eab58a480 100644
--- a/osu.Game.Rulesets.Karaoke/Beatmaps/Metadatas/PageInfo.cs
+++ b/osu.Game.Rulesets.Karaoke/Beatmaps/Metadatas/PageInfo.cs
@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Specialized;
+using System.Diagnostics;
 using System.Linq;
 using Newtonsoft.Json;
 using osu.Framework.Bindables;
@@ -30,12 +31,16 @@ public PageInfo()
             switch (args.Action)
             {
                 case NotifyCollectionChangedAction.Add:
+                    Debug.Assert(args.NewItems != null);
+
                     foreach (var c in args.NewItems.Cast<Page>())
                         c.TimeBindable.ValueChanged += timeValueChanged;
                     break;
 
                 case NotifyCollectionChangedAction.Reset:
                 case NotifyCollectionChangedAction.Remove:
+                    Debug.Assert(args.OldItems != null);
+
                     foreach (var c in args.OldItems.Cast<Page>())
                         c.TimeBindable.ValueChanged -= timeValueChanged;
                     break;
@@ -85,7 +90,7 @@ void onPageChanged()
 
     public PageInfo DeepClone()
     {
-        var controlPointInfo = (PageInfo)Activator.CreateInstance(GetType());
+        var controlPointInfo = (PageInfo)Activator.CreateInstance(GetType())!;
 
         return controlPointInfo;
     }
diff --git a/osu.Game.Rulesets.Karaoke/Bindables/BindableCultureInfo.cs b/osu.Game.Rulesets.Karaoke/Bindables/BindableCultureInfo.cs
index da9a1a5a5..4be103e91 100644
--- a/osu.Game.Rulesets.Karaoke/Bindables/BindableCultureInfo.cs
+++ b/osu.Game.Rulesets.Karaoke/Bindables/BindableCultureInfo.cs
@@ -26,11 +26,11 @@ public override void Parse(object? input)
             switch (input)
             {
                 case string str:
-                    Value = new CultureInfo(str);
+                    Value = CultureInfoUtils.CreateLoadCultureInfoByCode(str);
                     break;
 
                 case int lcid:
-                    Value = new CultureInfo(lcid);
+                    Value = CultureInfoUtils.CreateLoadCultureInfoById(lcid);
                     break;
 
                 case CultureInfo cultureInfo:
@@ -46,6 +46,6 @@ public override void Parse(object? input)
         protected override Bindable<CultureInfo?> CreateInstance() => new BindableCultureInfo();
 
         public override string ToString(string format, IFormatProvider formatProvider)
-            => CultureInfoUtils.GetLanguageDisplayText(Value);
+            => Value != null ? CultureInfoUtils.GetSaveCultureInfoCode(Value) : string.Empty;
     }
 }
diff --git a/osu.Game.Rulesets.Karaoke/Edit/ChangeHandlers/Lyrics/LyricTimeTagsChangeHandler.cs b/osu.Game.Rulesets.Karaoke/Edit/ChangeHandlers/Lyrics/LyricTimeTagsChangeHandler.cs
index aeaaef4f3..1023dfc4f 100644
--- a/osu.Game.Rulesets.Karaoke/Edit/ChangeHandlers/Lyrics/LyricTimeTagsChangeHandler.cs
+++ b/osu.Game.Rulesets.Karaoke/Edit/ChangeHandlers/Lyrics/LyricTimeTagsChangeHandler.cs
@@ -149,7 +149,8 @@ public void RemoveByPosition(TextIndex index)
                     return;
 
                 var removedTimeTag = matchedTimeTags.OrderBy(x => x.Time).FirstOrDefault();
-                lyric.TimeTags.Remove(removedTimeTag);
+                if (removedTimeTag != null)
+                    lyric.TimeTags.Remove(removedTimeTag);
             });
         }
 
diff --git a/osu.Game.Rulesets.Karaoke/Extensions/TrickyCompositeDrawableExtension.cs b/osu.Game.Rulesets.Karaoke/Extensions/TrickyCompositeDrawableExtension.cs
index e1a6abf26..c00e9b52f 100644
--- a/osu.Game.Rulesets.Karaoke/Extensions/TrickyCompositeDrawableExtension.cs
+++ b/osu.Game.Rulesets.Karaoke/Extensions/TrickyCompositeDrawableExtension.cs
@@ -24,7 +24,7 @@ public static class TrickyCompositeDrawableExtension
             if (prop == null)
                 return null;
 
-            return (IReadOnlyList<Drawable>)prop.GetValue(compositeDrawable);
+            return (IReadOnlyList<Drawable>)prop.GetValue(compositeDrawable)!;
         }
     }
 }
diff --git a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/DictionaryConverter.cs b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/DictionaryConverter.cs
index 1263a8ce0..b412afb38 100644
--- a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/DictionaryConverter.cs
+++ b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/DictionaryConverter.cs
@@ -9,7 +9,7 @@
 
 namespace osu.Game.Rulesets.Karaoke.IO.Serialization.Converters
 {
-    public abstract class DictionaryConverter<TKey, TValue> : JsonConverter<IDictionary<TKey, TValue>>
+    public abstract class DictionaryConverter<TKey, TValue> : JsonConverter<IDictionary<TKey, TValue>> where TKey : notnull
     {
         public sealed override IDictionary<TKey, TValue> ReadJson(JsonReader reader, Type objectType, IDictionary<TKey, TValue>? existingValue, bool hasExistingValue, JsonSerializer serializer)
         {
diff --git a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/GenericTypeConvertor.cs b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/GenericTypeConvertor.cs
index 5d29de9cf..611f0108f 100644
--- a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/GenericTypeConvertor.cs
+++ b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/GenericTypeConvertor.cs
@@ -24,7 +24,7 @@ public sealed override TType ReadJson(JsonReader reader, Type objectType, TType?
 
             var newReader = jObject.CreateReader();
 
-            var instance = (TType)Activator.CreateInstance(type);
+            var instance = (TType)Activator.CreateInstance(type)!;
             serializer.Populate(newReader, instance);
             PostProcessValue(instance, jObject, serializer);
             return instance;
diff --git a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/KaraokeSkinGroupConvertor.cs b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/KaraokeSkinGroupConvertor.cs
index 973851785..daaccc84f 100644
--- a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/KaraokeSkinGroupConvertor.cs
+++ b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/KaraokeSkinGroupConvertor.cs
@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Diagnostics;
 using System.Reflection;
 using osu.Game.Rulesets.Karaoke.Skinning.Groups;
 
@@ -13,7 +14,9 @@ protected override Type GetTypeByName(string name)
         {
             // only get name from font
             var assembly = Assembly.GetExecutingAssembly();
-            return assembly.GetType($"osu.Game.Rulesets.Karaoke.Skinning.Groups.{name}");
+            var type = assembly.GetType($"osu.Game.Rulesets.Karaoke.Skinning.Groups.{name}");
+            Debug.Assert(type != null);
+            return type;
         }
     }
 }
diff --git a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/KaraokeSkinMappingRoleConvertor.cs b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/KaraokeSkinMappingRoleConvertor.cs
index 23fde8b50..64d5cc450 100644
--- a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/KaraokeSkinMappingRoleConvertor.cs
+++ b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/KaraokeSkinMappingRoleConvertor.cs
@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Diagnostics;
 using System.Reflection;
 using osu.Game.Rulesets.Karaoke.Skinning.MappingRoles;
 
@@ -13,7 +14,9 @@ protected override Type GetTypeByName(string name)
         {
             // only get name from font
             var assembly = Assembly.GetExecutingAssembly();
-            return assembly.GetType($"osu.Game.Rulesets.Karaoke.Skinning.MappingRoles.{name}");
+            var type = assembly.GetType($"osu.Game.Rulesets.Karaoke.Skinning.MappingRoles.{name}");
+            Debug.Assert(type != null);
+            return type;
         }
     }
 }
diff --git a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/LyricConvertor.cs b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/LyricConvertor.cs
index 8d2a88b7d..6f8f31105 100644
--- a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/LyricConvertor.cs
+++ b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/LyricConvertor.cs
@@ -21,7 +21,7 @@ public override Lyric ReadJson(JsonReader reader, Type objectType, Lyric? existi
 
             var newReader = jObject.CreateReader();
 
-            var instance = (Lyric)Activator.CreateInstance(objectType);
+            var instance = (Lyric)Activator.CreateInstance(objectType)!;
             serializer.Populate(newReader, instance);
             return instance;
         }
diff --git a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/ReferenceLyricPropertyConfigConvertor.cs b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/ReferenceLyricPropertyConfigConvertor.cs
index 09676bb2c..921339aab 100644
--- a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/ReferenceLyricPropertyConfigConvertor.cs
+++ b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/ReferenceLyricPropertyConfigConvertor.cs
@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Diagnostics;
 using System.Reflection;
 using osu.Game.Rulesets.Karaoke.Objects.Properties;
 
@@ -12,7 +13,9 @@ public class ReferenceLyricPropertyConfigConvertor : GenericTypeConvertor<IRefer
         protected override Type GetTypeByName(string name)
         {
             var assembly = Assembly.GetExecutingAssembly();
-            return assembly.GetType($"osu.Game.Rulesets.Karaoke.Objects.Properties.{name}");
+            var type = assembly.GetType($"osu.Game.Rulesets.Karaoke.Objects.Properties.{name}");
+            Debug.Assert(type != null);
+            return type;
         }
     }
 }
diff --git a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/ShaderConvertor.cs b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/ShaderConvertor.cs
index 7a1fb13fc..9819e998b 100644
--- a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/ShaderConvertor.cs
+++ b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/ShaderConvertor.cs
@@ -36,7 +36,10 @@ protected override Type GetTypeByName(string name)
             // only get name from font
             var assembly = AssemblyUtils.GetAssemblyByName("osu.Framework.KaraokeFont");
             Debug.Assert(assembly != null);
-            return assembly.GetType($"osu.Framework.Graphics.Shaders.{name}");
+
+            var type = assembly.GetType($"osu.Framework.Graphics.Shaders.{name}");
+            Debug.Assert(type != null);
+            return type;
         }
     }
 }
diff --git a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/SingerConvertor.cs b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/SingerConvertor.cs
index 79a8fbde8..9958c2df1 100644
--- a/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/SingerConvertor.cs
+++ b/osu.Game.Rulesets.Karaoke/IO/Serialization/Converters/SingerConvertor.cs
@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Diagnostics;
 using System.Reflection;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
@@ -47,6 +48,8 @@ protected override void PostProcessJObject(JObject jObject, ISinger value, JsonS
     protected override Type GetTypeByName(string name)
     {
         var assembly = Assembly.GetExecutingAssembly();
-        return assembly.GetType($"osu.Game.Rulesets.Karaoke.Beatmaps.Metadatas.{name}");
+        var type = assembly.GetType($"osu.Game.Rulesets.Karaoke.Beatmaps.Metadatas.{name}");
+        Debug.Assert(type != null);
+        return type;
     }
 }
diff --git a/osu.Game.Rulesets.Karaoke/Objects/Lyric_Binding.cs b/osu.Game.Rulesets.Karaoke/Objects/Lyric_Binding.cs
index 66e0f33a8..0fd0fd5c9 100644
--- a/osu.Game.Rulesets.Karaoke/Objects/Lyric_Binding.cs
+++ b/osu.Game.Rulesets.Karaoke/Objects/Lyric_Binding.cs
@@ -24,12 +24,16 @@ private void initInternalBindingEvent()
                 switch (args.Action)
                 {
                     case NotifyCollectionChangedAction.Add:
+                        Debug.Assert(args.NewItems != null);
+
                         foreach (var c in args.NewItems.Cast<TimeTag>())
                             c.Changed += invalidate;
                         break;
 
                     case NotifyCollectionChangedAction.Reset:
                     case NotifyCollectionChangedAction.Remove:
+                        Debug.Assert(args.OldItems != null);
+
                         foreach (var c in args.OldItems.Cast<TimeTag>())
                             c.Changed -= invalidate;
                         break;
@@ -50,12 +54,16 @@ private void initInternalBindingEvent()
                 switch (args.Action)
                 {
                     case NotifyCollectionChangedAction.Add:
+                        Debug.Assert(args.NewItems != null);
+
                         foreach (var c in args.NewItems.Cast<RubyTag>())
                             c.Changed += invalidate;
                         break;
 
                     case NotifyCollectionChangedAction.Reset:
                     case NotifyCollectionChangedAction.Remove:
+                        Debug.Assert(args.OldItems != null);
+
                         foreach (var c in args.OldItems.Cast<RubyTag>())
                             c.Changed -= invalidate;
                         break;
@@ -69,12 +77,16 @@ private void initInternalBindingEvent()
                 switch (args.Action)
                 {
                     case NotifyCollectionChangedAction.Add:
+                        Debug.Assert(args.NewItems != null);
+
                         foreach (var c in args.NewItems.Cast<RomajiTag>())
                             c.Changed += invalidate;
                         break;
 
                     case NotifyCollectionChangedAction.Reset:
                     case NotifyCollectionChangedAction.Remove:
+                        Debug.Assert(args.OldItems != null);
+
                         foreach (var c in args.OldItems.Cast<RomajiTag>())
                             c.Changed -= invalidate;
                         break;
@@ -281,7 +293,7 @@ private void bindListValueChange<T>(ValueChangedEvent<Lyric?> e, Func<Lyric, IBi
                     triggerPropertyChanged();
             }
 
-            void propertyChanged(object sender, NotifyCollectionChangedEventArgs _) => triggerPropertyChanged();
+            void propertyChanged(object? sender, NotifyCollectionChangedEventArgs _) => triggerPropertyChanged();
 
             void triggerPropertyChanged()
             {
diff --git a/osu.Game.Rulesets.Karaoke/Objects/Tone.cs b/osu.Game.Rulesets.Karaoke/Objects/Tone.cs
index 6c30a4ebb..9b50e6856 100644
--- a/osu.Game.Rulesets.Karaoke/Objects/Tone.cs
+++ b/osu.Game.Rulesets.Karaoke/Objects/Tone.cs
@@ -49,7 +49,7 @@ public int CompareTo(int other)
 
         public bool Equals(int other) => Scale == other && Half == false;
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             return obj switch
             {
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/AutoGenerateSubsection.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/AutoGenerateSubsection.cs
index db86bfe0b..b81d541ec 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/AutoGenerateSubsection.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/AutoGenerateSubsection.cs
@@ -132,7 +132,7 @@ private Popover createSelectionPopover()
                     Children = AvailableSettings.Select(x =>
                     {
                         string name = GetDisplayName(x);
-                        return new OsuButton
+                        return new AutoGenerateButton
                         {
                             Text = name,
                             Width = 150,
@@ -148,5 +148,9 @@ private Popover createSelectionPopover()
                     }).ToList()
                 }
             };
+
+        private partial class AutoGenerateButton : EditorSectionButton
+        {
+        }
     }
 }
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/BindableBlueprintContainer.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/BindableBlueprintContainer.cs
index 3b24d9221..cdf30b89d 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/BindableBlueprintContainer.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/BindableBlueprintContainer.cs
@@ -5,6 +5,7 @@
 
 using System;
 using System.Collections.Specialized;
+using System.Diagnostics;
 using System.Linq;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
@@ -20,7 +21,7 @@ public abstract partial class BindableBlueprintContainer<T> : BlueprintContainer
         protected void RegisterBindable(BindableList<T> bindable)
         {
             if (bindableList != null)
-                throw new Exception();
+                throw new InvalidOperationException("Already have bindable.");
 
             bindableList = bindable;
 
@@ -30,12 +31,16 @@ protected void RegisterBindable(BindableList<T> bindable)
                 switch (args.Action)
                 {
                     case NotifyCollectionChangedAction.Add:
+                        Debug.Assert(args.NewItems != null);
+
                         foreach (var obj in args.NewItems.OfType<T>())
                             AddBlueprintFor(obj);
 
                         break;
 
                     case NotifyCollectionChangedAction.Remove:
+                        Debug.Assert(args.OldItems != null);
+
                         foreach (var obj in args.OldItems.OfType<T>())
                             RemoveBlueprintFor(obj);
 
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/Compose/BottomEditor/Notes/NoteEditor.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/Compose/BottomEditor/Notes/NoteEditor.cs
index 0975313d5..c3fff33cc 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/Compose/BottomEditor/Notes/NoteEditor.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/Compose/BottomEditor/Notes/NoteEditor.cs
@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Collections.Specialized;
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using osu.Framework.Allocation;
@@ -83,12 +84,16 @@ public NoteEditor()
                 switch (args.Action)
                 {
                     case NotifyCollectionChangedAction.Add:
+                        Debug.Assert(args.NewItems != null);
+
                         foreach (var obj in args.NewItems.OfType<Note>())
                             Playfield.Add(obj);
 
                         break;
 
                     case NotifyCollectionChangedAction.Remove:
+                        Debug.Assert(args.OldItems != null);
+
                         foreach (var obj in args.OldItems.OfType<Note>())
                             Playfield.Remove(obj);
 
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/LyricEditor.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/LyricEditor.cs
index 224cb262b..84c6e871a 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/LyricEditor.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/LyricEditor.cs
@@ -184,7 +184,7 @@ private void initialSubModeChanged<TSubMode>() where TSubMode : Enum
         {
             var editModeState = getEditModeState<TSubMode>();
             if (editModeState == null)
-                throw new NullReferenceException("Unknows sub mode.");
+                throw new ArgumentNullException();
 
             editModeState.BindableEditMode.BindValueChanged(e =>
             {
@@ -448,7 +448,7 @@ public void SwitchSubMode<TSubMode>(TSubMode subMode) where TSubMode : Enum
         {
             var editModeState = getEditModeState<TSubMode>();
             if (editModeState == null)
-                throw new NullReferenceException("Unknows sub mode.");
+                throw new ArgumentNullException();
 
             editModeState.ChangeEditMode(subMode);
         }
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/LyricList/Rows/Info/InfoControl.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/LyricList/Rows/Info/InfoControl.cs
index 7ab9f5130..caaed19e0 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/LyricList/Rows/Info/InfoControl.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/LyricList/Rows/Info/InfoControl.cs
@@ -191,7 +191,7 @@ private void initializeBadge(LyricEditorMode mode, Enum? subMode)
 
                     case LyricEditorMode.EditTimeTag:
                         if (subMode is not TimeTagEditMode timeTagEditMode)
-                            throw new NullReferenceException();
+                            throw new ArgumentNullException();
 
                         return createTimeTagModeSubInfo(timeTagEditMode, Lyric);
 
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/Settings/Reference/ReferenceLyricConfigSection.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/Settings/Reference/ReferenceLyricConfigSection.cs
index b34accbc5..3f61160ec 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/Settings/Reference/ReferenceLyricConfigSection.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/Settings/Reference/ReferenceLyricConfigSection.cs
@@ -92,7 +92,7 @@ public ReferenceLyricConfigSection()
                         break;
 
                     default:
-                        throw new IndexOutOfRangeException();
+                        throw new InvalidOperationException();
                 }
             });
 
@@ -166,7 +166,7 @@ private void onConfigChanged()
                     break;
 
                 default:
-                    throw new IndexOutOfRangeException();
+                    throw new ArgumentOutOfRangeException(nameof(config), config, "unknown config.");
             }
 
             isConfigChanging = false;
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/States/Modes/ModeStateWithBlueprintContainer.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/States/Modes/ModeStateWithBlueprintContainer.cs
index 1619669b8..17d4cbc50 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/States/Modes/ModeStateWithBlueprintContainer.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Lyrics/States/Modes/ModeStateWithBlueprintContainer.cs
@@ -64,7 +64,13 @@ protected virtual void TriggerDisableStateChanged()
             {
                 case CaretGenerateType.Action:
                     if (SelectFirstProperty(lyric))
-                        SelectedItems.Add(SelectableProperties(lyric).FirstOrDefault());
+                    {
+                        var firstItem = SelectableProperties(lyric).FirstOrDefault();
+
+                        if (firstItem != null)
+                            SelectedItems.Add(firstItem);
+                    }
+
                     break;
 
                 case CaretGenerateType.TargetLyric:
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Pages/Settings/PagesSection.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Pages/Settings/PagesSection.cs
index 9b9e738ab..2183cdba6 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Pages/Settings/PagesSection.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Pages/Settings/PagesSection.cs
@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Specialized;
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using osu.Framework.Allocation;
@@ -43,6 +44,8 @@ public PagesSection()
             switch (args.Action)
             {
                 case NotifyCollectionChangedAction.Add:
+                    Debug.Assert(args.NewItems != null);
+
                     foreach (var obj in args.NewItems.OfType<Page>())
                     {
                         Add(new LabelledPage(obj)
@@ -54,6 +57,8 @@ public PagesSection()
                     break;
 
                 case NotifyCollectionChangedAction.Remove:
+                    Debug.Assert(args.OldItems != null);
+
                     foreach (var obj in args.OldItems.OfType<Page>())
                     {
                         var drawable = Children.OfType<LabelledPage>().FirstOrDefault(x => x.Page == obj);
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Singers/Rows/Components/SingerAvatar.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Singers/Rows/Components/SingerAvatar.cs
index 97cd6f49b..b7bf059f7 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Singers/Rows/Components/SingerAvatar.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/Beatmaps/Singers/Rows/Components/SingerAvatar.cs
@@ -86,7 +86,7 @@ Task ICanAcceptFiles.Import(params string[] paths)
             return Task.CompletedTask;
         }
 
-        Task ICanAcceptFiles.Import(params ImportTask[] tasks) => throw new NotImplementedException();
+        Task ICanAcceptFiles.Import(ImportTask[] tasks, ImportParameters parameters) => throw new NotImplementedException();
 
         protected override void Dispose(bool isDisposing)
         {
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/Import/Lyrics/DragFile/DragFileStepScreen.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/Import/Lyrics/DragFile/DragFileStepScreen.cs
index 2566eb8f1..d73d6532e 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/Import/Lyrics/DragFile/DragFileStepScreen.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/Import/Lyrics/DragFile/DragFileStepScreen.cs
@@ -59,7 +59,7 @@ public Task Import(params string[] paths)
             return Task.CompletedTask;
         }
 
-        public Task Import(params ImportTask[] tasks)
+        public Task Import(ImportTask[] tasks, ImportParameters parameters = default)
         {
             // todo : wail until really implement needed.
             throw new NotImplementedException("Report to https://github.com/karaoke-dev/karaoke and i will implement it.");
diff --git a/osu.Game.Rulesets.Karaoke/Screens/Edit/Import/Lyrics/LyricImporterStepScreen.cs b/osu.Game.Rulesets.Karaoke/Screens/Edit/Import/Lyrics/LyricImporterStepScreen.cs
index 9e4e2b6db..661e088f7 100644
--- a/osu.Game.Rulesets.Karaoke/Screens/Edit/Import/Lyrics/LyricImporterStepScreen.cs
+++ b/osu.Game.Rulesets.Karaoke/Screens/Edit/Import/Lyrics/LyricImporterStepScreen.cs
@@ -42,7 +42,7 @@ protected LyricImporterStepScreen()
 
             InternalChildren = new Drawable[]
             {
-                new OsuButton
+                new LyricImporterStepButton
                 {
                     Anchor = Anchor.Centre,
                     Origin = Anchor.Centre,
@@ -89,5 +89,9 @@ public virtual void ConfirmRollBackFromStep(ILyricImporterStepScreen fromScreen,
         }
 
         public override string ToString() => Title;
+
+        private partial class LyricImporterStepButton : OsuButton
+        {
+        }
     }
 }
diff --git a/osu.Game.Rulesets.Karaoke/Utils/AssemblyUtils.cs b/osu.Game.Rulesets.Karaoke/Utils/AssemblyUtils.cs
index f7ec16875..cc1c96875 100644
--- a/osu.Game.Rulesets.Karaoke/Utils/AssemblyUtils.cs
+++ b/osu.Game.Rulesets.Karaoke/Utils/AssemblyUtils.cs
@@ -17,7 +17,7 @@ public static class AssemblyUtils
                 return defaultAssembly;
 
             // Note: because multiple assembly might be wrapped into single one by ILRepack, so should find by main dll again if not found.
-            return AppDomain.CurrentDomain.GetAssemblies().FirstOrDefault(x => x.FullName.Contains("osu.Game.Rulesets.Karaoke"));
+            return AppDomain.CurrentDomain.GetAssemblies().FirstOrDefault(x => x.FullName?.Contains("osu.Game.Rulesets.Karaoke") ?? false);
         }
     }
 }
diff --git a/osu.Game.Rulesets.Karaoke/Utils/BindablesUtils.cs b/osu.Game.Rulesets.Karaoke/Utils/BindablesUtils.cs
index c743d4073..d0f17a2fb 100644
--- a/osu.Game.Rulesets.Karaoke/Utils/BindablesUtils.cs
+++ b/osu.Game.Rulesets.Karaoke/Utils/BindablesUtils.cs
@@ -34,7 +34,7 @@ public static void OnyWaySync<T1, T2>(BindableList<T1> firstBindableList, Bindab
                 if (oldItems != null && oldItems.Count > 0)
                 {
                     // remove objects from second list if exist items has been removed.
-                    secondBindableList.RemoveAll(x => args.OldItems.Contains(x));
+                    secondBindableList.RemoveAll(x => oldItems.Contains(x));
                 }
             };
         }
diff --git a/osu.Game.Rulesets.Karaoke/osu.Game.Rulesets.Karaoke.csproj b/osu.Game.Rulesets.Karaoke/osu.Game.Rulesets.Karaoke.csproj
index 798570604..78cabbe4b 100644
--- a/osu.Game.Rulesets.Karaoke/osu.Game.Rulesets.Karaoke.csproj
+++ b/osu.Game.Rulesets.Karaoke/osu.Game.Rulesets.Karaoke.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup Label="Project">
-    <TargetFramework>netstandard2.1</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
     <AssemblyTitle>osu.Game.Rulesets.Karaoke</AssemblyTitle>
     <OutputType>Library</OutputType>
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -12,13 +12,13 @@
     <PackageReference Include="LanguageDetection.karaoke-dev" Version="1.3.3-alpha" />
     <PackageReference Include="LrcParser" Version="2022.529.1" />
     <PackageReference Include="Octokit" Version="4.0.3" />
-    <PackageReference Include="osu.Framework.KaraokeFont" Version="2022.1205.0" />
-    <PackageReference Include="osu.Framework.Microphone" Version="2022.1206.0" />
+    <PackageReference Include="osu.Framework.KaraokeFont" Version="2022.1219.0" />
+    <PackageReference Include="osu.Framework.Microphone" Version="2022.1227.2" />
     <PackageReference Include="ppy.LocalisationAnalyser" Version="2022.809.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="ppy.osu.Game" Version="2022.1207.0" />
+    <PackageReference Include="ppy.osu.Game" Version="2022.1225.1" />
     <PackageReference Include="Lucene.Net" Version="4.8.0-beta00016" />
     <PackageReference Include="Lucene.Net.Analysis.Kuromoji" Version="4.8.0-beta00016" />
     <PackageReference Include="NicoKaraParser" Version="1.1.0" />