Add auto focus to demo items search box (#1696)

* Add auto-focus on demo items search box

* Add HintAssist.IsFloating="True" to demo items search box

Author: AmRo045

MainDemo.Wpf/MainWindow.xaml

@@ -49,12 +49,14 @@
                         IsChecked="{Binding ElementName=MenuToggleButton, Path=IsChecked, Mode=TwoWay}" />
 
                     <TextBox 
+                        x:Name="DemoItemsSearchBox"
                         Text="{Binding SearchKeyword, UpdateSourceTrigger=PropertyChanged}"
                         DockPanel.Dock="Top"
                         Margin="16, 4"
                         Width="200"
                         BorderThickness="0"
-                        materialDesign:HintAssist.Hint="Search..."
+                        materialDesign:HintAssist.Hint="Search"
+                        materialDesign:HintAssist.IsFloating="True"
                         materialDesign:TextFieldAssist.HasClearButton="True"
                         materialDesign:TextFieldAssist.HasOutlinedTextField="True"
                         materialDesign:TextFieldAssist.DecorationVisibility="Collapsed"
@@ -82,9 +84,11 @@
                 <materialDesign:ColorZone Padding="16" materialDesign:ShadowAssist.ShadowDepth="Depth2"
                                             Mode="PrimaryMid" DockPanel.Dock="Top">
                     <DockPanel>
-
-                        <ToggleButton Style="{StaticResource MaterialDesignHamburgerToggleButton}" IsChecked="False"
-                                        x:Name="MenuToggleButton"/>
+                        <ToggleButton
+                            x:Name="MenuToggleButton"
+                            Style="{StaticResource MaterialDesignHamburgerToggleButton}"
+                            IsChecked="False"
+                            Click="MenuToggleButton_OnClick"/>
                         <materialDesign:PopupBox DockPanel.Dock="Right" PlacementMode="BottomAndAlignRightEdges" StaysOpen="False">
                             <StackPanel>
                                 <Button Content="Hello World" Click="MenuPopupButton_OnClick"/>

MainDemo.Wpf/MainWindow.xaml.cs

@@ -72,5 +72,10 @@ private void OnCopy(object sender, ExecutedRoutedEventArgs e)
                 }
             }
         }
+
+        private void MenuToggleButton_OnClick(object sender, RoutedEventArgs e)
+        {
+            DemoItemsSearchBox.Focus();
+        }
     }
 }