Fixing issue with ComboBoxes in dialog host

This revert the fix that was done for #3249.
Need to revisit fix that was done and find an alternative.

MaterialDesignThemes.UITests/Samples/DialogHost/WithComboBox.xaml

@@ -0,0 +1,38 @@
+<UserControl x:Class="MaterialDesignThemes.UITests.Samples.DialogHost.WithComboBox"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
+             xmlns:local="clr-namespace:MaterialDesignThemes.UITests.Samples.DialogHost"
+             mc:Ignorable="d" 
+             d:DesignHeight="450" d:DesignWidth="800">
+
+  <materialDesign:DialogHost x:Name="SampleDialogHost"
+                             Loaded="DialogHost_Loaded">
+    <materialDesign:DialogHost.DialogContent>
+      <Grid Margin="16">
+        <Grid.RowDefinitions>
+          <RowDefinition />
+          <RowDefinition />
+          <RowDefinition />
+        </Grid.RowDefinitions>
+        <TextBlock Text="Please choose the desired targeted platform "
+             Margin="6"
+             FontSize="12" 
+             TextWrapping="Wrap"/>
+        <ComboBox
+          x:Name="TargetedPlatformComboBox"
+          Grid.Row="1"
+          Width="120"
+          materialDesign:HintAssist.HelperText="Targetted Platform"
+          Style="{StaticResource MaterialDesignFloatingHintComboBox}">
+          <ComboBoxItem Content="Item1"/>
+          <ComboBoxItem Content="Item2" x:Name="TargetItem"/>
+          <ComboBoxItem Content="Item3"/>
+        </ComboBox>
+
+      </Grid>
+    </materialDesign:DialogHost.DialogContent>
+  </materialDesign:DialogHost>
+</UserControl>

MaterialDesignThemes.UITests/Samples/DialogHost/WithComboBox.xaml.cs

@@ -0,0 +1,17 @@
+namespace MaterialDesignThemes.UITests.Samples.DialogHost;
+
+/// <summary>
+/// Interaction logic for WithComboBox.xaml
+/// </summary>
+public partial class WithComboBox : UserControl
+{
+    public WithComboBox()
+    {
+        InitializeComponent();
+    }
+
+    private void DialogHost_Loaded(object sender, RoutedEventArgs e)
+    {
+        SampleDialogHost.IsOpen = true;
+    }
+}

MaterialDesignThemes.UITests/WPF/ComboBoxes/ComboBoxTests.cs

@@ -145,7 +145,7 @@ public async Task OnEditableComboBox_ClickInTextArea_FocusesTextBox()
         var editableTextBox = await comboBox.GetElement<TextBox>("PART_EditableTextBox");
         var button = await stackPanel.GetElement<Button>("Button");
 
-        // Open the combobox initially
+        // Open the ComboBox initially
         await comboBox.LeftClick(Position.RightCenter);
         await Task.Delay(50);   // Allow a little time for the drop-down to open (and property to change)
         bool wasOpenAfterClickOnToggleButton = await comboBox.GetIsDropDownOpen();

MaterialDesignThemes.UITests/WPF/DialogHosts/DialogHostTests.cs

@@ -478,6 +478,32 @@ public async Task DialogHost_ChangesSelectedRailItem_DoesNotPerformRailChangeWhe
         Assert.True(await railItem1.GetIsSelected());
         Assert.False(await railItem2.GetIsSelected());
 
+        recorder.Success();
+    }
+
+    [Fact]
+    [Description("Issue 3450")]
+    public async Task DialogHost_WithComboBox_CanSelectItem()
+    {
+        await using var recorder = new TestRecorder(App);
+
+        IVisualElement dialogHost = await LoadUserControl<WithComboBox>();
+
+        var comboBox = await dialogHost.GetElement<ComboBox>("TargetedPlatformComboBox");
+        await Task.Delay(500);
+        await comboBox.LeftClick();
+
+        var item = await Wait.For(() => comboBox.GetElement<ComboBoxItem>("TargetItem"));
+        await Task.Delay(TimeSpan.FromSeconds(1));
+        await item.LeftClick();
+
+        await Wait.For(async () =>
+        {
+            var index = await comboBox.GetSelectedIndex();
+            Assert.Equal(1, index);
+        });
+
+
         recorder.Success();
     }
 }

MaterialDesignThemes.Wpf/DialogHost.cs

@@ -957,7 +957,7 @@ private void OnPreviewGotKeyboardFocus(object sender, KeyboardFocusChangedEventA
         if (_popup != null &&
             PresentationSource.FromVisual(_popup.Child) is HwndSource hwndSource)
         {
-            SetFocus(hwndSource.Handle);
+            //SetFocus(hwndSource.Handle);
         }
     }