Made MaxTokens non-nullable and added checks for DP.UnsetValue

Author: shweaver-MSFT

Microsoft.Toolkit.Uwp.UI.Controls.Input/TokenizingTextBox/TokenizingTextBox.Properties.cs

@@ -162,13 +162,13 @@ private static void TextPropertyChanged(DependencyObject d, DependencyPropertyCh
         /// </summary>
         public static readonly DependencyProperty MaxTokensProperty = DependencyProperty.Register(
             nameof(MaxTokens),
-            typeof(int?),
+            typeof(int),
             typeof(TokenizingTextBox),
-            new PropertyMetadata(null, OnMaxTokensChanged));
+            new PropertyMetadata(DependencyProperty.UnsetValue, OnMaxTokensChanged));
 
         private static void OnMaxTokensChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
         {
-            if (d is TokenizingTextBox ttb && e.NewValue is int newMaxTokens)
+            if (d is TokenizingTextBox ttb && ttb.ReadLocalValue(MaxTokensProperty) != DependencyProperty.UnsetValue && e.NewValue is int newMaxTokens)
             {
                 var tokenCount = ttb.Items.Count;
                 if (tokenCount > newMaxTokens)
@@ -347,9 +347,9 @@ public string SelectedTokenText
         /// <summary>
         /// Gets or sets the maximum number of token results allowed at a time.
         /// </summary>
-        public int? MaxTokens
+        public int MaxTokens
         {
-            get => (int?)GetValue(MaxTokensProperty);
+            get => (int)GetValue(MaxTokensProperty);
             set => SetValue(MaxTokensProperty, value);
         }
     }

Microsoft.Toolkit.Uwp.UI.Controls.Input/TokenizingTextBox/TokenizingTextBox.cs

@@ -78,10 +78,10 @@ private void ItemsSource_PropertyChanged(DependencyObject sender, DependencyProp
             {
                 _innerItemsSource = new InterspersedObservableCollection(ItemsSource);
 
-                if (MaxTokens.HasValue && _innerItemsSource.ItemsSource.Count > MaxTokens)
+                if (ReadLocalValue(MaxTokensProperty) != DependencyProperty.UnsetValue && _innerItemsSource.ItemsSource.Count > MaxTokens)
                 {
                     // Reduce down to the max as necessary.
-                    for (var i = _innerItemsSource.ItemsSource.Count - 1; i >= Math.Max(MaxTokens.Value, 0); --i)
+                    for (var i = _innerItemsSource.ItemsSource.Count - 1; i >= Math.Max(MaxTokens, 0); --i)
                     {
                         _innerItemsSource.Remove(_innerItemsSource[i]);
                     }
@@ -440,7 +440,7 @@ public async Task ClearAsync()
 
         internal async Task AddTokenAsync(object data, bool? atEnd = null)
         {
-            if (MaxTokens <= 0)
+            if (ReadLocalValue(MaxTokensProperty) != DependencyProperty.UnsetValue && MaxTokens <= 0)
             {
                 // No tokens for you
                 return;
@@ -465,7 +465,7 @@ internal async Task AddTokenAsync(object data, bool? atEnd = null)
             // If we've been typing in the last box, just add this to the end of our collection
             if (atEnd == true || _currentTextEdit == _lastTextEdit)
             {
-                if (MaxTokens != null && _innerItemsSource.ItemsSource.Count >= MaxTokens)
+                if (ReadLocalValue(MaxTokensProperty) != DependencyProperty.UnsetValue && _innerItemsSource.ItemsSource.Count >= MaxTokens)
                 {
                     // Remove tokens from the end until below the max number.
                     for (var i = _innerItemsSource.Count - 2; i >= 0; --i)
@@ -493,7 +493,7 @@ internal async Task AddTokenAsync(object data, bool? atEnd = null)
                 var edit = _currentTextEdit;
                 var index = _innerItemsSource.IndexOf(edit);
 
-                if (MaxTokens != null && _innerItemsSource.ItemsSource.Count >= MaxTokens)
+                if (ReadLocalValue(MaxTokensProperty) != DependencyProperty.UnsetValue && _innerItemsSource.ItemsSource.Count >= MaxTokens)
                 {
                     // Find the next token and remove it, until below the max number of tokens.
                     for (var i = index; i < _innerItemsSource.Count;  i++)