diff --git a/src/Net_40/HandyControl_Net_40/Themes/Theme.xaml b/src/Net_40/HandyControl_Net_40/Themes/Theme.xaml
index 8b417c6b6..0f9c9cdee 100644
--- a/src/Net_40/HandyControl_Net_40/Themes/Theme.xaml
+++ b/src/Net_40/HandyControl_Net_40/Themes/Theme.xaml
@@ -11703,8 +11703,9 @@
 		<Setter Property="Stylus.IsFlicksEnabled" Value="False" />
 		<Setter Property="Padding" Value="{StaticResource DefaultInputPadding}" />
 		<Setter Property="VerticalContentAlignment" Value="Center" />
-		<Setter Property="Validation.ErrorTemplate" Value="{x:Null}" />
-		<Setter Property="ItemContainerStyle" Value="{StaticResource AutoCompleteTextBoxItemBaseStyle}" />
+        <Setter Property="Validation.ErrorTemplate" Value="{x:Null}" />
+        <Setter Property="VirtualizingStackPanel.IsVirtualizing" Value="True"/>
+        <Setter Property="ItemContainerStyle" Value="{StaticResource AutoCompleteTextBoxItemBaseStyle}" />
 		<Setter Property="IsTabStop" Value="false" />
 		<Setter Property="hc:Empty.ShowEmpty" Value="True" />
 		<Setter Property="Template">
@@ -11712,10 +11713,10 @@
 				<ControlTemplate TargetType="hc:AutoCompleteTextBox">
 					<hc:SimplePanel>
 						<Border CornerRadius="{Binding Path=(hc:BorderElement.CornerRadius),RelativeSource={RelativeSource TemplatedParent}}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="true">
-							<TextBox x:Name="PART_SearchTextBox" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" IsReadOnly="{Binding IsReadOnly, RelativeSource={RelativeSource TemplatedParent}}" CaretBrush="{TemplateBinding CaretBrush}" Padding="{TemplateBinding Padding}" Style="{StaticResource ComboBoxEditableTextBox}" />
+							<TextBox x:Name="PART_SearchTextBox" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" IsReadOnly="{Binding IsReadOnly, RelativeSource={RelativeSource TemplatedParent}}" CaretBrush="{TemplateBinding CaretBrush}" Padding="{TemplateBinding Padding}" Style="{StaticResource ComboBoxEditableTextBox}" Text="{TemplateBinding Text}" />
 						</Border>
 						<Popup x:Name="PART_Popup" AllowsTransparency="true" IsOpen="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" Margin="1" PopupAnimation="{StaticResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}" Placement="Bottom">
-							<Border BorderThickness="0,1,0,0" Effect="{StaticResource EffectShadow2}" Margin="8,0,8,8" CornerRadius="{Binding Path=(hc:BorderElement.CornerRadius),RelativeSource={RelativeSource TemplatedParent}}" x:Name="dropDownBorder" MinWidth="{Binding ActualWidth, ElementName=toggleButton}" MaxHeight="{TemplateBinding MaxDropDownHeight}" BorderBrush="{DynamicResource BorderBrush}" Background="{DynamicResource RegionBrush}">
+							<Border BorderThickness="0,1,0,0" Effect="{StaticResource EffectShadow2}" Margin="8,0,8,8" CornerRadius="{Binding Path=(hc:BorderElement.CornerRadius),RelativeSource={RelativeSource TemplatedParent}}" x:Name="dropDownBorder" MinWidth="{Binding ActualWidth, ElementName=dropDownBorder}" MaxHeight="{TemplateBinding MaxDropDownHeight}" BorderBrush="{DynamicResource BorderBrush}" Background="{DynamicResource RegionBrush}">
 								<hc:ToggleBlock IsChecked="{Binding HasItems,RelativeSource={RelativeSource TemplatedParent},Mode=OneWay}" VerticalContentAlignment="Stretch" HorizontalContentAlignment="Stretch">
 									<hc:ToggleBlock.CheckedContent>
 										<ScrollViewer Margin="0,4">
@@ -11761,7 +11762,18 @@
 				</ControlTemplate>
 			</Setter.Value>
 		</Setter>
-	</Style>
+        <Style.Triggers>
+            <Trigger Property="VirtualizingPanel.IsVirtualizing" Value="true">
+                <Setter Property="ItemsPanel">
+                    <Setter.Value>
+                        <ItemsPanelTemplate>
+                            <VirtualizingStackPanel/>
+                        </ItemsPanelTemplate>
+                    </Setter.Value>
+                </Setter>
+            </Trigger>
+        </Style.Triggers>
+    </Style>
 	<Style x:Key="DataGridCellStyle" TargetType="DataGridCell">
 		<Setter Property="FocusVisualStyle">
 			<Setter.Value>
@@ -14361,4 +14373,4 @@
 	</Style>
 	<Style BasedOn="{StaticResource RangeSliderBaseStyle}" TargetType="hc:RangeSlider" />
 	<Style BasedOn="{StaticResource SliderBaseStyle}" TargetType="Slider" />
-</ResourceDictionary>
\ No newline at end of file
+</ResourceDictionary>
diff --git a/src/Shared/HandyControlDemo_Shared/UserControl/Controls/AutoCompleteTextBoxDemoCtl.xaml b/src/Shared/HandyControlDemo_Shared/UserControl/Controls/AutoCompleteTextBoxDemoCtl.xaml
index 3721593a7..20285bda3 100644
--- a/src/Shared/HandyControlDemo_Shared/UserControl/Controls/AutoCompleteTextBoxDemoCtl.xaml
+++ b/src/Shared/HandyControlDemo_Shared/UserControl/Controls/AutoCompleteTextBoxDemoCtl.xaml
@@ -5,6 +5,6 @@
              xmlns:hc="https://handyorg.github.io/handycontrol"
              DataContext="{Binding AutoCompleteTextBoxDemo, Source={StaticResource Locator}}">
     <hc:TransitioningContentControl>
-        <hc:AutoCompleteTextBox Width="380" VerticalAlignment="Center" HorizontalAlignment="Center" Margin="32" ItemsSource="{Binding Items}" Text="{Binding SearchText}" DisplayMemberPath="Name"/>
+        <hc:AutoCompleteTextBox Width="380" VerticalAlignment="Center" HorizontalAlignment="Center" Margin="32" ItemsSource="{Binding Items}" DisplayMemberPath="Name"/>
     </hc:TransitioningContentControl>
 </UserControl>
diff --git a/src/Shared/HandyControlDemo_Shared/ViewModel/Controls/AutoCompleteTextBoxDemoViewModel.cs b/src/Shared/HandyControlDemo_Shared/ViewModel/Controls/AutoCompleteTextBoxDemoViewModel.cs
index f655aadc9..7b41a8388 100644
--- a/src/Shared/HandyControlDemo_Shared/ViewModel/Controls/AutoCompleteTextBoxDemoViewModel.cs
+++ b/src/Shared/HandyControlDemo_Shared/ViewModel/Controls/AutoCompleteTextBoxDemoViewModel.cs
@@ -1,6 +1,5 @@
 using System.Collections.Generic;
 using GalaSoft.MvvmLight;
-using HandyControl.Collections;
 using HandyControlDemo.Data;
 using HandyControlDemo.Service;
 
@@ -8,49 +7,10 @@ namespace HandyControlDemo.ViewModel;
 
 public class AutoCompleteTextBoxDemoViewModel : ViewModelBase
 {
-    private string _searchText;
-
-    public string SearchText
-    {
-        get => _searchText;
-#if NET40
-        set
-        {
-            Set(nameof(SearchText), ref _searchText, value);
-            FilterItems(value);
-        }
-#else
-        set
-        {
-            Set(ref _searchText, value);
-            FilterItems(value);
-        }
-#endif
-    }
-
-    public ManualObservableCollection<DemoDataModel> Items { get; set; } = new();
-
-    private readonly List<DemoDataModel> _dataList;
+    public List<DemoDataModel> Items { get; set; }
 
     public AutoCompleteTextBoxDemoViewModel(DataService dataService)
     {
-        _dataList = dataService.GetDemoDataList(10);
-    }
-
-    private void FilterItems(string key)
-    {
-        Items.CanNotify = false;
-
-        Items.Clear();
-
-        foreach (var data in _dataList)
-        {
-            if (data.Name.ToLower().Contains(key.ToLower()))
-            {
-                Items.Add(data);
-            }
-        }
-
-        Items.CanNotify = true;
+        Items = dataService.GetDemoDataList(10);
     }
 }
diff --git a/src/Shared/HandyControl_Shared/Controls/Input/AutoCompleteTextBox/AutoCompleteTextBox.cs b/src/Shared/HandyControl_Shared/Controls/Input/AutoCompleteTextBox/AutoCompleteTextBox.cs
index 178989dae..59419d88e 100644
--- a/src/Shared/HandyControl_Shared/Controls/Input/AutoCompleteTextBox/AutoCompleteTextBox.cs
+++ b/src/Shared/HandyControl_Shared/Controls/Input/AutoCompleteTextBox/AutoCompleteTextBox.cs
@@ -1,4 +1,5 @@
-using System.Windows;
+using System;
+using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Input;
 using HandyControl.Data;
@@ -15,8 +16,6 @@ public class AutoCompleteTextBox : ComboBox
 
     private System.Windows.Controls.TextBox _searchTextBox;
 
-    private object _selectedItem;
-
     static AutoCompleteTextBox()
     {
         TextProperty.OverrideMetadata(typeof(AutoCompleteTextBox), new FrameworkPropertyMetadata(default(string), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
@@ -40,18 +39,14 @@ public override void OnApplyTemplate()
             _searchTextBox.PreviewKeyDown += SearchTextBoxKeyDown;
             _searchTextBox.TextChanged += SearchTextBoxTextChanged;
         }
-
-        UpdateTextBoxBySelectedItem(_selectedItem);
     }
 
     protected override void OnSelectionChanged(SelectionChangedEventArgs e)
     {
-        base.OnSelectionChanged(e);
-
         if (e.AddedItems.Count > 0)
         {
-            _selectedItem = e.AddedItems[0];
-            UpdateTextBoxBySelectedItem(_selectedItem);
+            var selectedItem = e.AddedItems[0];
+            UpdateTextBoxBySelectedItem(selectedItem);
         }
     }
 
@@ -61,7 +56,6 @@ protected override void OnSelectionChanged(SelectionChangedEventArgs e)
 
     private void SearchTextBoxTextChanged(object sender, TextChangedEventArgs e)
     {
-        _selectedItem = null;
         SelectedIndex = -1;
 
         if (ignoreTextChanging)
@@ -78,6 +72,7 @@ private void SearchTextBoxTextChanged(object sender, TextChangedEventArgs e)
         }
         else if (_searchTextBox.IsFocused)
         {
+            Items.Filter = FilterItem ?? DefaultFilter;
             SetCurrentValue(IsDropDownOpenProperty, ValueBoxes.TrueBox);
         }
     }
@@ -152,7 +147,17 @@ private void SearchTextBoxGotFocus(object sender, RoutedEventArgs e)
     {
         if (!string.IsNullOrEmpty(Text))
         {
+            Items.Filter = FilterItem ?? DefaultFilter;
             SetCurrentValue(IsDropDownOpenProperty, ValueBoxes.TrueBox);
         }
     }
+
+
+    public Predicate<object> FilterItem { get; set; }
+
+	private bool DefaultFilter(object item)
+	{
+		var text = BindingHelper.GetString(item, DisplayMemberPath);
+		return text.ToLower().Contains(Text.ToLower());
+	}
 }
diff --git a/src/Shared/HandyControl_Shared/Themes/Styles/Base/AutoCompleteTextBoxBaseStyle.xaml b/src/Shared/HandyControl_Shared/Themes/Styles/Base/AutoCompleteTextBoxBaseStyle.xaml
index ba02cd2b5..85b6f0081 100644
--- a/src/Shared/HandyControl_Shared/Themes/Styles/Base/AutoCompleteTextBoxBaseStyle.xaml
+++ b/src/Shared/HandyControl_Shared/Themes/Styles/Base/AutoCompleteTextBoxBaseStyle.xaml
@@ -52,6 +52,7 @@
         <Setter Property="Padding" Value="{StaticResource DefaultInputPadding}"/>
         <Setter Property="VerticalContentAlignment" Value="Center"/>
         <Setter Property="Validation.ErrorTemplate" Value="{x:Null}"/>
+        <Setter Property="VirtualizingStackPanel.IsVirtualizing" Value="True"/>
         <Setter Property="ItemContainerStyle" Value="{StaticResource AutoCompleteTextBoxItemBaseStyle}"/>
         <Setter Property="IsTabStop" Value="false"/>
         <Setter Property="hc:Empty.ShowEmpty" Value="True"/>
@@ -60,10 +61,10 @@
                 <ControlTemplate TargetType="hc:AutoCompleteTextBox">
                     <hc:SimplePanel>
                         <Border CornerRadius="{Binding Path=(hc:BorderElement.CornerRadius),RelativeSource={RelativeSource TemplatedParent}}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="true">
-                            <TextBox x:Name="PART_SearchTextBox" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" IsReadOnly="{Binding IsReadOnly, RelativeSource={RelativeSource TemplatedParent}}" CaretBrush="{TemplateBinding CaretBrush}" Padding="{TemplateBinding Padding}" Style="{StaticResource ComboBoxEditableTextBox}"/>
+                            <TextBox x:Name="PART_SearchTextBox" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" IsReadOnly="{Binding IsReadOnly, RelativeSource={RelativeSource TemplatedParent}}" CaretBrush="{TemplateBinding CaretBrush}" Padding="{TemplateBinding Padding}" Style="{StaticResource ComboBoxEditableTextBox}" Text="{TemplateBinding Text}" />
                         </Border>
                         <Popup x:Name="PART_Popup" AllowsTransparency="true" IsOpen="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" Margin="1" PopupAnimation="{StaticResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}" Placement="Bottom">
-                            <Border BorderThickness="0,1,0,0" Effect="{StaticResource EffectShadow2}" Margin="8,0,8,8" CornerRadius="{Binding Path=(hc:BorderElement.CornerRadius),RelativeSource={RelativeSource TemplatedParent}}" x:Name="dropDownBorder" MinWidth="{Binding ActualWidth, ElementName=toggleButton}" MaxHeight="{TemplateBinding MaxDropDownHeight}" BorderBrush="{DynamicResource BorderBrush}" Background="{DynamicResource RegionBrush}">
+                            <Border BorderThickness="0,1,0,0" Effect="{StaticResource EffectShadow2}" Margin="8,0,8,8" CornerRadius="{Binding Path=(hc:BorderElement.CornerRadius),RelativeSource={RelativeSource TemplatedParent}}" x:Name="dropDownBorder" MinWidth="{Binding ActualWidth, ElementName=dropDownBorder}" MaxHeight="{TemplateBinding MaxDropDownHeight}" BorderBrush="{DynamicResource BorderBrush}" Background="{DynamicResource RegionBrush}">
                                 <hc:ToggleBlock IsChecked="{Binding HasItems,RelativeSource={RelativeSource TemplatedParent},Mode=OneWay}" VerticalContentAlignment="Stretch" HorizontalContentAlignment="Stretch">
                                     <hc:ToggleBlock.CheckedContent>
                                         <ScrollViewer Margin="0,4">
@@ -109,6 +110,17 @@
                 </ControlTemplate>
             </Setter.Value>
         </Setter>
+        <Style.Triggers>
+            <Trigger Property="VirtualizingPanel.IsVirtualizing" Value="true">
+                <Setter Property="ItemsPanel">
+                    <Setter.Value>
+                        <ItemsPanelTemplate>
+                            <VirtualizingStackPanel/>
+                        </ItemsPanelTemplate>
+                    </Setter.Value>
+                </Setter>
+            </Trigger>
+        </Style.Triggers>
     </Style>
 
 </ResourceDictionary>
diff --git a/src/Shared/HandyControl_Shared/Themes/Theme.xaml b/src/Shared/HandyControl_Shared/Themes/Theme.xaml
index fd777b2f2..9cfbcec97 100644
--- a/src/Shared/HandyControl_Shared/Themes/Theme.xaml
+++ b/src/Shared/HandyControl_Shared/Themes/Theme.xaml
@@ -11840,6 +11840,7 @@
 		<Setter Property="Padding" Value="{StaticResource DefaultInputPadding}" />
 		<Setter Property="VerticalContentAlignment" Value="Center" />
 		<Setter Property="Validation.ErrorTemplate" Value="{x:Null}" />
+		<Setter Property="VirtualizingStackPanel.IsVirtualizing" Value="True" />
 		<Setter Property="ItemContainerStyle" Value="{StaticResource AutoCompleteTextBoxItemBaseStyle}" />
 		<Setter Property="IsTabStop" Value="false" />
 		<Setter Property="hc:Empty.ShowEmpty" Value="True" />
@@ -11848,10 +11849,10 @@
 				<ControlTemplate TargetType="hc:AutoCompleteTextBox">
 					<hc:SimplePanel>
 						<Border CornerRadius="{Binding Path=(hc:BorderElement.CornerRadius),RelativeSource={RelativeSource TemplatedParent}}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="true">
-							<TextBox x:Name="PART_SearchTextBox" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" IsReadOnly="{Binding IsReadOnly, RelativeSource={RelativeSource TemplatedParent}}" CaretBrush="{TemplateBinding CaretBrush}" Padding="{TemplateBinding Padding}" Style="{StaticResource ComboBoxEditableTextBox}" />
+							<TextBox x:Name="PART_SearchTextBox" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" IsReadOnly="{Binding IsReadOnly, RelativeSource={RelativeSource TemplatedParent}}" CaretBrush="{TemplateBinding CaretBrush}" Padding="{TemplateBinding Padding}" Style="{StaticResource ComboBoxEditableTextBox}" Text="{TemplateBinding Text}" />
 						</Border>
 						<Popup x:Name="PART_Popup" AllowsTransparency="true" IsOpen="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" Margin="1" PopupAnimation="{StaticResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}" Placement="Bottom">
-							<Border BorderThickness="0,1,0,0" Effect="{StaticResource EffectShadow2}" Margin="8,0,8,8" CornerRadius="{Binding Path=(hc:BorderElement.CornerRadius),RelativeSource={RelativeSource TemplatedParent}}" x:Name="dropDownBorder" MinWidth="{Binding ActualWidth, ElementName=toggleButton}" MaxHeight="{TemplateBinding MaxDropDownHeight}" BorderBrush="{DynamicResource BorderBrush}" Background="{DynamicResource RegionBrush}">
+							<Border BorderThickness="0,1,0,0" Effect="{StaticResource EffectShadow2}" Margin="8,0,8,8" CornerRadius="{Binding Path=(hc:BorderElement.CornerRadius),RelativeSource={RelativeSource TemplatedParent}}" x:Name="dropDownBorder" MinWidth="{Binding ActualWidth, ElementName=dropDownBorder}" MaxHeight="{TemplateBinding MaxDropDownHeight}" BorderBrush="{DynamicResource BorderBrush}" Background="{DynamicResource RegionBrush}">
 								<hc:ToggleBlock IsChecked="{Binding HasItems,RelativeSource={RelativeSource TemplatedParent},Mode=OneWay}" VerticalContentAlignment="Stretch" HorizontalContentAlignment="Stretch">
 									<hc:ToggleBlock.CheckedContent>
 										<ScrollViewer Margin="0,4">
@@ -11897,6 +11898,17 @@
 				</ControlTemplate>
 			</Setter.Value>
 		</Setter>
+		<Style.Triggers>
+			<Trigger Property="VirtualizingPanel.IsVirtualizing" Value="true">
+				<Setter Property="ItemsPanel">
+					<Setter.Value>
+						<ItemsPanelTemplate>
+							<VirtualizingStackPanel />
+						</ItemsPanelTemplate>
+					</Setter.Value>
+				</Setter>
+			</Trigger>
+		</Style.Triggers>
 	</Style>
 	<Style x:Key="DataGridCellStyle" TargetType="DataGridCell">
 		<Setter Property="FocusVisualStyle">