Fix #81: "GetFilter().Clear" doesn't clear the Listbox of the MultipleChoiceFilter

Author: tom-englert

src/DataGridExtensions/MultipleChoiceFilter.cs

@@ -154,7 +154,9 @@ public override void OnApplyTemplate()
             var listBox = _listBox = Template?.FindName("PART_ListBox", this) as ListBox;
             if (listBox == null)
                 return;
+
             listBox.SelectionChanged += ListBox_SelectionChanged;
+            listBox.Loaded += ListBox_Loaded;
 
             var filterColumnControl = this.FindAncestorOrSelf<DataGridFilterColumnControl>();
 
@@ -170,15 +172,7 @@ public override void OnApplyTemplate()
 
             _dataGrid.SetTrackFocusedCell(true);
 
-            var filter = Filter;
-
-            if (filter?.Items == null && listBox.IsLoaded)
-            {
-                listBox.SelectAll();
-            }
-
             var items = (INotifyCollectionChanged)listBox.Items;
-
             items.CollectionChanged += ListBox_ItemsCollectionChanged;
         }
 
@@ -235,6 +229,11 @@ private void ListBox_ItemsCollectionChanged(object? sender, NotifyCollectionChan
             }
         }
 
+        private void ListBox_Loaded(object sender, RoutedEventArgs e)
+        {
+            Filter_Changed();
+        }
+
         private void Filter_Changed()
         {
             var listBox = _listBox;
@@ -247,10 +246,7 @@ private void Filter_Changed()
 
             if (filter?.Items == null)
             {
-                if (listBox.IsLoaded)
-                {
-                    listBox.SelectAll();
-                }
+                listBox.SelectAll();
                 return;
             }
 

src/DataGridExtensionsSample/DataGridExtensionsSample.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
   <PropertyGroup>
-    <TargetFrameworks>net5.0-windows7.0</TargetFrameworks>
+    <TargetFrameworks>net6.0-windows7.0</TargetFrameworks>
     <UseWPF>true</UseWPF>
     <OutputType>WinExe</OutputType>
     <GenerateAssemblyInfo>true</GenerateAssemblyInfo>

src/DataGridExtensionsSample/Views/Customized2View.xaml

@@ -70,6 +70,8 @@
           <Decorator Width="10" />
           <Button x:Name="OpenAndPopulateAFilterButton" VerticalAlignment="Top" Padding="5,2" Command="{Binding OpenAndPopulateAFilterCommand}">Open &amp; Populate a Filter</Button>
           <Decorator Width="10" />
+          <Button x:Name="ClearFilter" VerticalAlignment="Top" Padding="5,2" Command="{Binding ClearFilterCommand}" CommandParameter="{Binding ElementName=DemoDataGrid}">Clear Filter</Button>
+          <Decorator Width="10" />
           <Button x:Name="ProgrammaticAccessToFilterControlButton" VerticalAlignment="Top" Padding="5,2" Command="{Binding ProgrammaticAccessToFilterControlCommand}">Change Popup Caption</Button>
         </StackPanel>
         <StackPanel Orientation="Horizontal" DockPanel.Dock="Bottom" HorizontalAlignment="Right">

src/DataGridExtensionsSample/Views/Customized2ViewModel.cs

@@ -4,6 +4,7 @@
     using System.Collections.Generic;
     using System.Collections.ObjectModel;
     using System.ComponentModel;
+    using System.Windows.Controls;
     using System.Windows.Input;
 
     using DataGridExtensions;
@@ -42,6 +43,14 @@ public Customized2ViewModel(DataProvider dataProvider)
         public Predicate<object> GlobalFilter { get; } = item => (item as DataItem)?.Column1?.Contains('7') ?? false;
 #pragma warning restore CA1307 // Specify StringComparison for clarity
 
+
+        public ICommand ClearFilterCommand => new DelegateCommand<DataGrid>(ClearFilter);
+
+        private void ClearFilter(DataGrid? dataGrid)
+        {
+            dataGrid?.GetFilter().Clear();
+        }
+
         public ICommand ClearIpsumCommand => new DelegateCommand(ClearIpsum);
 
         private void ClearIpsum()