Hi,
I am trying ScrolViewer in WPF and .. it does not work. I see the ScrolViewer in design mode but it disappears when my app is running. Can someone help me why ?
Design Mode:

Running time:

Here is XAML code:
<Window x:Class="WpfApp.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApp"
mc:Ignorable="d"
Title="MainWindow" Height="480" Width="800" MaxWidth="800" MaxHeight="480">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="500" />
<ColumnDefinition Width="300" MaxWidth="300"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="40" />
<RowDefinition Height="440" />
</Grid.RowDefinitions>
<DockPanel Grid.Column="0" Grid.Row="0">
<Menu DockPanel.Dock="Top">
<MenuItem Header="_File" FontSize="24" FontFamily="Arial">
<MenuItem Header="_New" >
<MenuItem.Icon>
<Image Source="c:\1\WPF-01\Button-Previous-icon.png" />
</MenuItem.Icon>
</MenuItem>
<MenuItem Header="_Open" />
<MenuItem Header="_Save" />
<Separator />
<MenuItem Header="_Exit" />
</MenuItem>
</Menu>
</DockPanel>
<Button Grid.Column="0" Grid.Row="1" x:Name="btn001" Content="Hello" Width="200" Height="200" Click="btn001_Click" />
<TabControl Grid.Column="1" Grid.Row="1"
Width="300"
MaxWidth="300"
Height="440"
VerticalAlignment="Top">
<TabItem Header="TabItem" ClipToBounds="True" >
<Grid Background="#FFE5E5E5"
Margin="-4,-4,0,0"
Height="Auto"
VerticalAlignment="Stretch"
HorizontalAlignment="Stretch"
>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="300" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="400" />
</Grid.RowDefinitions>
<ScrollViewer Grid.Column="0" Grid.Row="0"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
VerticalScrollBarVisibility="Visible"
HorizontalScrollBarVisibility="Visible"
Margin="0,0,0,0"
Padding="0,0"
>
<StackPanel Name="stackPanel1"
Width="310"
Height="800"
MaxWidth="310">
<GroupBox HorizontalAlignment="Left"
VerticalAlignment="Top"
Header="Text"
Margin="4,4,0,0"
Padding="0,0"
Height="401"
Width="180"
Background="White" >
</GroupBox>
</StackPanel>
</ScrollViewer>
</Grid>
</TabItem>
<TabItem Header="TabItem">
<Grid Background="#FFE5E5E5"/>
</TabItem>
</TabControl>
</Grid>
</Window>