From dc0d231bdbc1e8f6512603060c624f01afe551b9 Mon Sep 17 00:00:00 2001
From: michael-hawker <24302614+michael-hawker@users.noreply.github.com>
Date: Sat, 30 May 2020 03:08:28 -0700
Subject: [PATCH 1/6] Remove commented out XAML in style

---
 .../TokenizingTextBoxItem.AutoSuggestBox.xaml               | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml
index 95651105749..b425b225a5e 100644
--- a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml
+++ b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml
@@ -290,17 +290,12 @@
     <Style x:Key="TokenizingTextBoxItemTextStyle" TargetType="controls:TokenizingTextBoxItem">
         <Setter Property="Background" Value="{ThemeResource SystemControlBackgroundChromeMediumLowBrush}" />
         <Setter Property="BorderBrush" Value="{ThemeResource SystemControlTransparentBrush}" />
-        <!-- <Setter Property="BorderThickness" Value="{StaticResource TokenizingTextBoxItemBorderThickness}" />
-        <Setter Property="HorizontalContentAlignment" Value="{StaticResource TokenizingTextBoxItemHorizontalContentAlignment}" />
-        <Setter Property="Padding" Value="{StaticResource TokenizingTextBoxItemPadding}" />
-        <Setter Property="VerticalContentAlignment" Value="{StaticResource TokenizingTextBoxItemVerticalContentAlignment}" />-->
         <Setter Property="IsTabStop" Value="False" />
         <Setter Property="UseSystemFocusVisuals" Value="False" />
         <Setter Property="MinWidth" Value="128" />
         <Setter Property="Template">
             <Setter.Value>
                 <ControlTemplate TargetType="controls:TokenizingTextBoxItem">
-                    <!-- TODO: Thinking we should just give a reference to the parent for each item when we construct the container? -->
                     <AutoSuggestBox Name="PART_AutoSuggestBox"
                                     UpdateTextOnSelect="False"
                                     DisplayMemberPath="{Binding Path=Owner.DisplayMemberPath, RelativeSource={RelativeSource Mode=TemplatedParent}}"
@@ -311,7 +306,6 @@
                                     Style="{StaticResource SystemAutoSuggestBoxStyle}"
                                     Text="{Binding Text, Mode=TwoWay}"
                                     TextBoxStyle="{StaticResource TokenizingTextBoxTextBoxStyle}"/>
-                    <!-- TODO: Visual State to style autosuggestbox based on focus? -->
                 </ControlTemplate>
             </Setter.Value>
         </Setter>

From d68b119705352374b28a3ab6b2331368823d06b2 Mon Sep 17 00:00:00 2001
From: michael-hawker <24302614+michael-hawker@users.noreply.github.com>
Date: Wed, 3 Jun 2020 01:06:56 -0700
Subject: [PATCH 2/6] Add TokenizingTextBox Workaround for IconSource FontSize
 Styling issue

Ref https://github.com/microsoft/microsoft-ui-xaml/issues/2568
Also added WPF TryFindResource method to LogicalTree helpers - thanks for review/assist @rudyhuyn
---
 .../SamplePages/TabView/TabViewPage.xaml.cs   |  2 +-
 .../TokenizingTextBoxXaml.bind                |  4 +--
 .../TokenizingTextBox/TokenizingTextBox.xaml  |  1 +
 .../TokenizingTextBoxItem.AutoSuggestBox.cs   |  9 ++++++
 .../TokenizingTextBoxItem.AutoSuggestBox.xaml |  4 ++-
 .../Extensions/Tree/LogicalTree.cs            | 32 +++++++++++++++++++
 6 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/Microsoft.Toolkit.Uwp.SampleApp/SamplePages/TabView/TabViewPage.xaml.cs b/Microsoft.Toolkit.Uwp.SampleApp/SamplePages/TabView/TabViewPage.xaml.cs
index 7f0c212e516..643fdcfb38c 100644
--- a/Microsoft.Toolkit.Uwp.SampleApp/SamplePages/TabView/TabViewPage.xaml.cs
+++ b/Microsoft.Toolkit.Uwp.SampleApp/SamplePages/TabView/TabViewPage.xaml.cs
@@ -69,5 +69,5 @@ private void Tabs_TabDraggedOutside(object sender, TabDraggedOutsideEventArgs e)
             TabViewNotification.Show("Tore Tab '" + str + "' Outside of TabView.", 2000);
         }
         #pragma warning restore CS0618 // Type or member is obsolete
-    }    
+    }
 }
diff --git a/Microsoft.Toolkit.Uwp.SampleApp/SamplePages/TokenizingTextBox/TokenizingTextBoxXaml.bind b/Microsoft.Toolkit.Uwp.SampleApp/SamplePages/TokenizingTextBox/TokenizingTextBoxXaml.bind
index 287385ad55a..e9aca6ebd2a 100644
--- a/Microsoft.Toolkit.Uwp.SampleApp/SamplePages/TokenizingTextBox/TokenizingTextBoxXaml.bind
+++ b/Microsoft.Toolkit.Uwp.SampleApp/SamplePages/TokenizingTextBox/TokenizingTextBoxXaml.bind
@@ -16,7 +16,7 @@
       <controls:TokenizingTextBox
           x:Name="TokenBox"
           PlaceholderText="Add Actions"
-          QueryIcon="{ex:SymbolIconSource Glyph=Setting, FontSize=16}"
+          QueryIcon="{ex:SymbolIconSource Glyph=Setting}"
           MaxHeight="104"
           HorizontalAlignment="Stretch"
           TextMemberPath="Text"
@@ -52,7 +52,7 @@
             PlaceholderText="Select Names"
             MaxHeight="104"
             HorizontalAlignment="Stretch"
-            QueryIcon="{ex:SymbolIconSource Glyph=Find, FontSize=16}"
+            QueryIcon="{ex:SymbolIconSource Glyph=Find}"
             TextMemberPath="Text"
             TokenDelimiter=","
             IsItemClickEnabled="True">
diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml
index ab583789a1a..102b9016025 100644
--- a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml
+++ b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml
@@ -12,6 +12,7 @@
     <Thickness x:Key="TokenizingTextBoxPresenterMargin">0,0,6,0</Thickness>
     <x:Double x:Key="TokenizingTextBoxTokenSpacing">2</x:Double>
     <Thickness x:Key="TextControlBorderThemeThicknessFocused">2</Thickness>
+    <x:Double x:Key="TokenizingTextBoxIconFontSize">16</x:Double>
 
     <controls:TokenizingTextBoxStyleSelector x:Key="TokenizingTextBoxStyleSelector"
                                              TextStyle="{StaticResource TokenizingTextBoxItemTextStyle}"
diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.cs b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.cs
index 827455c37d2..5249da78907 100644
--- a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.cs
+++ b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.cs
@@ -101,6 +101,15 @@ private void OnApplyTemplateAutoSuggestBox(AutoSuggestBox auto)
                 // Setup a binding to the QueryIcon of the Parent if we're the last box.
                 if (Content is PretokenStringContainer str && str.IsLast)
                 {
+                    // Workaround for https://github.com/microsoft/microsoft-ui-xaml/issues/2568
+                    if (Owner.QueryIcon is FontIconSource fis &&
+                        fis.ReadLocalValue(FontIconSource.FontSizeProperty) == DependencyProperty.UnsetValue)
+                    {
+                        // This can be expensive, could we optimize?
+                        // Also, this is changing the FontSize on the IconSource (which could be shared?)
+                        fis.FontSize = Owner.TryFindResource("TokenizingTextBoxIconFontSize") as double? ?? 16;
+                    }
+
                     var iconBinding = new Binding()
                     {
                         Source = Owner,
diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml
index b425b225a5e..088ae69fe29 100644
--- a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml
+++ b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml
@@ -15,12 +15,14 @@
                           Background="{ThemeResource TextControlButtonBackground}"
                           BorderBrush="{ThemeResource TextControlButtonBorderBrush}"
                           BorderThickness="{TemplateBinding BorderThickness}">
+                        <!-- FontSize is ignored here, see https://github.com/microsoft/microsoft-ui-xaml/issues/2568 -->
+                        <!-- Set in code-behind link:TokenizingTextBoxItem.AutoSuggestBox.cs#L104 -->
                         <TextBlock x:Name="GlyphElement"
                                    HorizontalAlignment="Center"
                                    VerticalAlignment="Center"
                                    AutomationProperties.AccessibilityView="Raw"
                                    FontFamily="{ThemeResource SymbolThemeFontFamily}"
-                                   FontSize="{ThemeResource AutoSuggestBoxIconFontSize}"
+                                   FontSize="{ThemeResource TokenizingTextBoxIconFontSize}"
                                    FontStyle="Normal"
                                    Foreground="{ThemeResource TextControlButtonForeground}"
                                    Text="&#xE10A;" />
diff --git a/Microsoft.Toolkit.Uwp.UI/Extensions/Tree/LogicalTree.cs b/Microsoft.Toolkit.Uwp.UI/Extensions/Tree/LogicalTree.cs
index b4be056d43f..df77539061b 100644
--- a/Microsoft.Toolkit.Uwp.UI/Extensions/Tree/LogicalTree.cs
+++ b/Microsoft.Toolkit.Uwp.UI/Extensions/Tree/LogicalTree.cs
@@ -286,5 +286,37 @@ private static string ContentPropertySearch(Type type)
 
             return ContentPropertySearch(type.GetTypeInfo().BaseType);
         }
+
+        /// <summary>
+        /// Provides a WPF compatible version of TryFindResource to provide a static resource lookup.
+        /// If the key is not found in the current element's resources, the logical tree is then searched element-by-element to look for the resource in each element's resources.
+        /// If none of the elements contain the resource, the Application's resources are then searched.
+        /// <seealso href="https://docs.microsoft.com/en-us/dotnet/api/system.windows.frameworkelement.tryfindresource"/>
+        /// <seealso href="https://docs.microsoft.com/en-us/dotnet/desktop-wpf/fundamentals/xaml-resources-define#static-resource-lookup-behavior"/>
+        /// </summary>
+        /// <param name="start"><see cref="FrameworkElement"/> to start searching for Resource.</param>
+        /// <param name="resourceKey">Key to search for.</param>
+        /// <returns>Requested resource or null.</returns>
+        public static object TryFindResource(this FrameworkElement start, object resourceKey)
+        {
+            object value = null;
+            var current = start;
+
+            // Look in our dictionary and then walk-up parents
+            while (current != null)
+            {
+                if (current.Resources?.TryGetValue(resourceKey, out value) == true)
+                {
+                    return value;
+                }
+
+                current = current.Parent as FrameworkElement;
+            }
+
+            // Finally try application resources.
+            Application.Current?.Resources?.TryGetValue(resourceKey, out value);
+
+            return value;
+        }
     }
 }

From 3cb6f236eedbbb86d3be6856d1a60972789ec9a2 Mon Sep 17 00:00:00 2001
From: michael-hawker <24302614+michael-hawker@users.noreply.github.com>
Date: Wed, 3 Jun 2020 01:13:11 -0700
Subject: [PATCH 3/6] Add comment about resource value which is hard-coded in
 code-behind for initial value of TokenizingTextBoxItem

---
 .../TokenizingTextBox/TokenizingTextBox.xaml                    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml
index 102b9016025..2e7aa06398b 100644
--- a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml
+++ b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml
@@ -12,7 +12,7 @@
     <Thickness x:Key="TokenizingTextBoxPresenterMargin">0,0,6,0</Thickness>
     <x:Double x:Key="TokenizingTextBoxTokenSpacing">2</x:Double>
     <Thickness x:Key="TextControlBorderThemeThicknessFocused">2</Thickness>
-    <x:Double x:Key="TokenizingTextBoxIconFontSize">16</x:Double>
+    <x:Double x:Key="TokenizingTextBoxIconFontSize">16</x:Double> <!-- 'Example' hard-coded currently in link:TokenizingTextBoxItem.AutoSuggestBox.cs#L110, but can be overwritten in developer's resources as 'normal' -->
 
     <controls:TokenizingTextBoxStyleSelector x:Key="TokenizingTextBoxStyleSelector"
                                              TextStyle="{StaticResource TokenizingTextBoxItemTextStyle}"

From b0cf73500578c2ff4d2c437caaa1fc8f776bd25c Mon Sep 17 00:00:00 2001
From: michael-hawker <24302614+michael-hawker@users.noreply.github.com>
Date: Wed, 3 Jun 2020 02:08:06 -0700
Subject: [PATCH 4/6] Fix issue with style location causing crash for
 TokenizingTextBox

---
 .../TokenizingTextBox/TokenizingTextBox.xaml                   | 3 +--
 .../TokenizingTextBoxItem.AutoSuggestBox.xaml                  | 3 ++-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml
index 2e7aa06398b..2bad43277c0 100644
--- a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml
+++ b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.xaml
@@ -12,8 +12,7 @@
     <Thickness x:Key="TokenizingTextBoxPresenterMargin">0,0,6,0</Thickness>
     <x:Double x:Key="TokenizingTextBoxTokenSpacing">2</x:Double>
     <Thickness x:Key="TextControlBorderThemeThicknessFocused">2</Thickness>
-    <x:Double x:Key="TokenizingTextBoxIconFontSize">16</x:Double> <!-- 'Example' hard-coded currently in link:TokenizingTextBoxItem.AutoSuggestBox.cs#L110, but can be overwritten in developer's resources as 'normal' -->
-
+    
     <controls:TokenizingTextBoxStyleSelector x:Key="TokenizingTextBoxStyleSelector"
                                              TextStyle="{StaticResource TokenizingTextBoxItemTextStyle}"
                                              TokenStyle="{StaticResource TokenizingTextBoxItemTokenStyle}"/>
diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml
index 088ae69fe29..61506d7540e 100644
--- a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml
+++ b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBoxItem.AutoSuggestBox.xaml
@@ -4,7 +4,8 @@
 
     <!--<Thickness x:Key="ButtonPadding">8,4,8,5</Thickness> Not sure if we'll also need this later-->
     <Thickness x:Key="TextControlThemePadding">10,3,6,6</Thickness><!-- Need local copy of this, as including WinUI overrides this to something that adds too much padding for our inner box -->
-    
+    <x:Double x:Key="TokenizingTextBoxIconFontSize">16</x:Double><!-- 'Example' hard-coded currently in link:TokenizingTextBoxItem.AutoSuggestBox.cs#L110, but can be overwritten in developer's resources as 'normal' -->
+
     <!--#region Button Styles -->
     <Style x:Key="TokenizingTextBoxDeleteButtonStyle"
            TargetType="Button">

From 051856cf55808076af7d8a5b74d4c7b1e1423e72 Mon Sep 17 00:00:00 2001
From: michael-hawker <24302614+michael-hawker@users.noreply.github.com>
Date: Wed, 3 Jun 2020 03:00:51 -0700
Subject: [PATCH 5/6] Add 'simple' workaround to TokenizingTextBox
 AutoSuggestBox Layout Issue

This was an issue with the PlaceholderText ContentControl in the AutoSuggestBox which would not update it's layout properly when the ASB had focus when we would add/remove a token.
---
 .../TokenizingTextBox/TokenizingTextBox.cs    | 31 ++++++++++++
 .../Helpers/CompositionTargetHelper.cs        | 50 +++++++++++++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 Microsoft.Toolkit.Uwp.UI/Helpers/CompositionTargetHelper.cs

diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.cs b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.cs
index 5f0cb22f0df..753cca8e9d8 100644
--- a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.cs
+++ b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.cs
@@ -8,6 +8,8 @@
 using System.Threading.Tasks;
 using Microsoft.Toolkit.Uwp.Deferred;
 using Microsoft.Toolkit.Uwp.Extensions;
+using Microsoft.Toolkit.Uwp.UI.Extensions;
+using Microsoft.Toolkit.Uwp.UI.Helpers;
 using Windows.System;
 using Windows.UI.Core;
 using Windows.UI.Xaml;
@@ -435,6 +437,8 @@ internal async Task AddTokenAsync(object data, bool? atEnd = null)
             last?._autoSuggestTextBox.Focus(FocusState.Keyboard);
 
             TokenItemAdded?.Invoke(this, data);
+
+            GuardAgainstPlaceholderTextLayoutIssue();
         }
 
         private void UpdateCurrentTextEdit(PretokenStringContainer edit)
@@ -475,7 +479,34 @@ private async Task<bool> RemoveTokenAsync(TokenizingTextBoxItem item, object dat
 
             TokenItemRemoved?.Invoke(this, data);
 
+            GuardAgainstPlaceholderTextLayoutIssue();
+
             return true;
         }
+
+        private void GuardAgainstPlaceholderTextLayoutIssue()
+        {
+            // If the *PlaceholderText is visible* on the last AutoSuggestBox, it can incorrectly layout itself
+            // when the *ASB has focus*. We think this is an optimization in the platform, but haven't been able to
+            // isolate a straight-reproduction of this issue outside of this control (though we have eliminated
+            // most Toolkit influences like ASB/TextBox Style, the InterspersedObservableCollection, etc...).
+            // The only Toolkit component involved here should be WrapPanel (which is a straight-forward Panel).
+            // We also know the ASB itself is adjusting it's size correctly, it's the inner component.
+            //
+            // To combat this issue:
+            //   We toggle the visibility of the Placeholder ContentControl in order to force it's layout to update properly
+            var placeholder = ContainerFromItem(_lastTextEdit).FindDescendantByName("PlaceholderTextContentPresenter");
+
+            if (placeholder.Visibility == Visibility.Visible)
+            {
+                placeholder.Visibility = Visibility.Collapsed;
+
+                // After we ensure we've hid the control, make it visible again (this is inperceptable to the user).
+                _ = CompositionTargetHelper.ExecuteAfterCompositionRenderingAsync(() =>
+                {
+                    placeholder.Visibility = Visibility.Visible;
+                });
+            }
+        }
     }
 }
diff --git a/Microsoft.Toolkit.Uwp.UI/Helpers/CompositionTargetHelper.cs b/Microsoft.Toolkit.Uwp.UI/Helpers/CompositionTargetHelper.cs
new file mode 100644
index 00000000000..08a6741cf50
--- /dev/null
+++ b/Microsoft.Toolkit.Uwp.UI/Helpers/CompositionTargetHelper.cs
@@ -0,0 +1,50 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading.Tasks;
+using Microsoft.Toolkit.Diagnostics;
+using Windows.UI.Xaml.Media;
+
+namespace Microsoft.Toolkit.Uwp.UI.Helpers
+{
+    /// <summary>
+    /// Provides helpers for the <see cref="CompositionTarget"/> class.
+    /// </summary>
+    public static class CompositionTargetHelper
+    {
+        /// <summary>
+        /// Provides a method to execute code after the rendering pass is completed.
+        /// <seealso href="https://github.com/microsoft/microsoft-ui-xaml/blob/c045cde57c5c754683d674634a0baccda34d58c4/dev/dll/SharedHelpers.cpp#L399"/>
+        /// </summary>
+        /// <param name="action">Action to be executed after render pass</param>
+        /// <returns>Awaitable Task</returns>
+        public static Task<bool> ExecuteAfterCompositionRenderingAsync(Action action)
+        {
+            Guard.IsNotNull(action, nameof(action));
+
+            var taskCompletionSource = new TaskCompletionSource<bool>();
+
+            try
+            {
+                void Callback(object sender, object args)
+                {
+                    CompositionTarget.Rendering -= Callback;
+
+                    action();
+
+                    taskCompletionSource.SetResult(true);
+                }
+
+                CompositionTarget.Rendering += Callback;
+            }
+            catch (Exception e)
+            {
+                taskCompletionSource.SetException(e); // Note this can just sometimes be a wrong thread exception, see WinUI function notes.
+            }
+
+            return taskCompletionSource.Task;
+        }
+    }
+}

From f7737e417c362f0644ec24bcbc4d624a00081ec8 Mon Sep 17 00:00:00 2001
From: Marcus Perryman <marcpe@microsoft.com>
Date: Wed, 3 Jun 2020 12:10:47 +0100
Subject: [PATCH 6/6] add null check for UX UT

---
 .../TokenizingTextBox/TokenizingTextBox.cs                      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.cs b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.cs
index 753cca8e9d8..1c1731e5105 100644
--- a/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.cs
+++ b/Microsoft.Toolkit.Uwp.UI.Controls/TokenizingTextBox/TokenizingTextBox.cs
@@ -497,7 +497,7 @@ private void GuardAgainstPlaceholderTextLayoutIssue()
             //   We toggle the visibility of the Placeholder ContentControl in order to force it's layout to update properly
             var placeholder = ContainerFromItem(_lastTextEdit).FindDescendantByName("PlaceholderTextContentPresenter");
 
-            if (placeholder.Visibility == Visibility.Visible)
+            if (placeholder?.Visibility == Visibility.Visible)
             {
                 placeholder.Visibility = Visibility.Collapsed;