diff --git a/Core/Models/TagDatabase/TagDatabase.ImportMethods.cs b/Core/Models/TagDatabase/TagDatabase.ImportMethods.cs
index a833858..7e0e7b1 100644
--- a/Core/Models/TagDatabase/TagDatabase.ImportMethods.cs
+++ b/Core/Models/TagDatabase/TagDatabase.ImportMethods.cs
@@ -28,7 +28,7 @@ public partial class TagDatabase
             // phase 2: add the parents and aliases.
             foreach (var tag in importDict.Values)
             {
-                var currentTag = this.Tags.SingleOrDefault(t => t.Name == tag.Name);
+                var currentTag = this.Tags.Single(t => t.Name == tag.Name);
 
                 var parentIds = tag.Parents.Select(parentName => nameToId[parentName]).ToList();
 
@@ -47,6 +47,8 @@ public partial class TagDatabase
 
     private async Task WriteImportedParentsToDatabase(SqliteTransaction transaction, int targetId, List<int> parentIds)
     {
+        if (this._currentConnection is null)
+            throw new InvalidOperationException(ErrorMessages.TagDatabaseNotInitialised);
         var valuesClauses = new List<string>();
         var parameters = new List<SqliteParameter>();
 
diff --git a/Core/Models/TagDatabase/TagDatabase.cs b/Core/Models/TagDatabase/TagDatabase.cs
index 1d6db23..5588b11 100644
--- a/Core/Models/TagDatabase/TagDatabase.cs
+++ b/Core/Models/TagDatabase/TagDatabase.cs
@@ -21,7 +21,7 @@ public partial class TagDatabase
     private const string TopLevelColumnName = "top_level";
     private SqliteConnection? _currentConnection;
 
-    private List<string> _defaultBindings = ["genre"];
+    private readonly List<string> _defaultBindings = ["genre"];
 
     /// <summary>
     ///     Initializes a new instance of the <see cref="TagDatabase" /> class.
@@ -45,7 +45,7 @@ public partial class TagDatabase
     ///     Gets or sets a List(string) of tag binding(s) that will be added to a tag by default. Defaults to <i>genre</i>
     ///     (e.g. Festival Progressive House::genre).
     /// </summary>
-    public List<string> DefaultTagBindings { get; set; }
+    public List<string> DefaultTagBindings { get; set; } = [];
 
     /// <summary>
     ///     Gets the location of the .thdb file associated with the <see cref="TagDatabase" />, inferred from the current
diff --git a/UI/ViewModels/HierarchyTreeViewModel.cs b/UI/ViewModels/HierarchyTreeViewModel.cs
index 5e56708..fae7aa6 100644
--- a/UI/ViewModels/HierarchyTreeViewModel.cs
+++ b/UI/ViewModels/HierarchyTreeViewModel.cs
@@ -265,7 +265,7 @@ public partial class HierarchyTreeViewModel : ViewModelBase, IDisposable
 
     // public ICommand NewTagCommand => this._mainWindow.NewTagCommand;
     // ReSharper disable once PartialMethodParameterNameMismatch
-    partial void OnSelectedTagChanged(TagItemViewModel? _, TagItemViewModel? newValue)
+    partial void OnSelectedTagChanged(TagItemViewModel? oldValue, TagItemViewModel? newValue)
     {
         if (newValue is null || this._mainWindow.SelectedTagId == newValue.Id) return;
         this._mainWindow.SelectedTag = newValue;
diff --git a/UI/ViewModels/TagItemViewModel.cs b/UI/ViewModels/TagItemViewModel.cs
index 65de304..151987e 100644
--- a/UI/ViewModels/TagItemViewModel.cs
+++ b/UI/ViewModels/TagItemViewModel.cs
@@ -21,8 +21,6 @@ public partial class TagItemViewModel(Tag tag, Func<List<int>, List<string>> get
 
     [ObservableProperty] private string _editingTagBindings = string.Empty;
 
-    private bool _isInitialising;
-
     public string Aliases =>
         this.Tag.Aliases.Count > 0
             ? string.Join("; ", this.Tag.Aliases)
@@ -58,7 +56,6 @@ public partial class TagItemViewModel(Tag tag, Func<List<int>, List<string>> get
 
     public void BeginEdit()
     {
-        this._isInitialising = true;
         this.EditingName = this.Tag.Name;
 
         if (this.OnDatabase || string.IsNullOrEmpty(this.EditingParents))
@@ -68,7 +65,6 @@ public partial class TagItemViewModel(Tag tag, Func<List<int>, List<string>> get
         this.EditingTagBindings = this.CurrentTagBindings;
         this.EditingAliases = this.Aliases;
         this.EditingNotes = this.CurrentNotes;
-        this._isInitialising = false;
     }
 
     public void CommitEdit(Tag savedTag)
@@ -87,7 +83,6 @@ public partial class TagItemViewModel(Tag tag, Func<List<int>, List<string>> get
 
     public void RefreshParentsString()
     {
-        this._isInitialising = true;
         this.OnPropertyChanged(nameof(this.CurrentParentsString));
         var newParents = this.CurrentParentsString;
         if (!string.IsNullOrEmpty(newParents))
@@ -95,8 +90,6 @@ public partial class TagItemViewModel(Tag tag, Func<List<int>, List<string>> get
             this.EditingParents = newParents;
             this.OnPropertyChanged(nameof(this.EditingParents));
         }
-
-        this._isInitialising = false;
     }
 
     public void RefreshSelf()
diff --git a/UI/Views/ValueConverters/AllNotNullOrEmptyConverter.cs b/UI/Views/ValueConverters/AllNotNullOrEmptyConverter.cs
index 97f8452..a284215 100644
--- a/UI/Views/ValueConverters/AllNotNullOrEmptyConverter.cs
+++ b/UI/Views/ValueConverters/AllNotNullOrEmptyConverter.cs
@@ -10,7 +10,7 @@ public class AllNotNullOrEmptyMultiConverter : IMultiValueConverter
 {
     public static readonly AllNotNullOrEmptyMultiConverter Instance = new();
 
-    public object Convert(IList<object?> values, Type targetType, object parameter, CultureInfo culture)
+    public object Convert(IList<object?> values, Type targetType, object? parameter, CultureInfo culture)
     {
         return values.All(v => v is string s ? !string.IsNullOrEmpty(s) : v is not null);
     }
diff --git a/UI/Views/ValueConverters/AnyNotNullOrEmptyConverter.cs b/UI/Views/ValueConverters/AnyNotNullOrEmptyConverter.cs
index a38c6ac..f61d8c8 100644
--- a/UI/Views/ValueConverters/AnyNotNullOrEmptyConverter.cs
+++ b/UI/Views/ValueConverters/AnyNotNullOrEmptyConverter.cs
@@ -10,7 +10,7 @@ public class AnyNotNullOrEmptyMultiConverter : IMultiValueConverter
 {
     public static readonly AnyNotNullOrEmptyMultiConverter Instance = new();
 
-    public object Convert(IList<object?> values, Type targetType, object parameter, CultureInfo culture)
+    public object Convert(IList<object?> values, Type targetType, object? parameter, CultureInfo culture)
     {
         return values.Any(v => v is string s ? !string.IsNullOrEmpty(s) : v is not null);
     }
diff --git a/UI/Views/ValueConverters/TruncationConverter.cs b/UI/Views/ValueConverters/TruncationConverter.cs
index 00db90b..426b74c 100644
--- a/UI/Views/ValueConverters/TruncationConverter.cs
+++ b/UI/Views/ValueConverters/TruncationConverter.cs
@@ -8,7 +8,7 @@ public class TruncationConverter : IValueConverter
 {
     public static readonly TruncationConverter Instance = new();
 
-    public object Convert(object? value, Type targetType, object parameter, CultureInfo culture)
+    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
     {
         if (value is not string s) return value;
         var limit = parameter is string p && int.TryParse(p, out var l) ? l : 50;