ScrollViewer not showing scroll far without fixed height

Question

I have the below XAML. The issue that I cannot seem to solve is that I have a scroll viewer that is wrapping around a grid full of views (with a fixed height) but cannot get the scroll bars to scroll on content longer than the window size.

I want the user control to fill the full hight of the window but also be scrollable when the amount of grid controls length is greater than the window size. But if I do not set the height of the scroll viewer manually then I will never get the scrollable scrollbar (manually set in the example).

I have looked at other examples on the site but cannot come across a valid answer (including this link).

XAML:

<UserControl d:DesignWidth="300" d:DataContext="{d:DesignInstance ViewModels:EntityViewModel}">
    <StackPanel>
        <Label Content=“text” />
        <ScrollViewer Height="450" Width="250" VerticalScrollBarVisibility="auto">
            <Grid>
                <ItemsControl ItemsSource="{Binding Entities}">
                    <ItemsControl.ItemTemplate>
                        <DataTemplate>
                            <local:EntityView DataContext="{Binding}" />
                        </DataTemplate>
                    </ItemsControl.ItemTemplate>
                </ItemsControl>
            </Grid>
        </ScrollViewer>
    </StackPanel>
</UserControl>

Edit:
I'm adding an additional example which can be easily recreated. The need is to be able to have the scroll view to be scrollable with the dock panel (can be a grid) has more content than can fit on the screen of which the user control is inserted (which means I can't have a fixed size on the scroll viewer).

<Window Title="MainWindow" Height="200" Width="300">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="200" />
        </Grid.ColumnDefinitions>


        <StackPanel Grid.Column="0">
            <Label Content="title"/>
            <ScrollViewer>
                <DockPanel>
                    <Label DockPanel.Dock="Top" Content="title" HorizontalContentAlignment="Center" />
                    <Label DockPanel.Dock="Top" Content="title" HorizontalContentAlignment="Center" />
                    <Label DockPanel.Dock="Top" Content="title" HorizontalContentAlignment="Center" />
                    <Label DockPanel.Dock="Top" Content="title" HorizontalContentAlignment="Center" />
                    <Label DockPanel.Dock="Top" Content="title" HorizontalContentAlignment="Center" />
                    <Label DockPanel.Dock="Top" Content="title" HorizontalContentAlignment="Center" />
                    <Label DockPanel.Dock="Top" Content="title" HorizontalContentAlignment="Center" />
                </DockPanel>
            </ScrollViewer>
        </StackPanel>
    </Grid>
</Window>

Answer 1

A StackPanel with vertical Orientation does not limit the height of its child elements. In other words, the Scrollviewer will always be as high as it need to be show its entire content, unless you explicitly set its Height.

You'll have to choose a different Panel, e.g. a Grid or a DockPanel:

<UserControl ...>
    <DockPanel>
        <Label DockPanel.Dock="Top" Content="text"/>
        <ScrollViewer VerticalScrollBarVisibility="Auto">
            <ItemsControl ItemsSource="{Binding Entities}">
                ...
            </ItemsControl>
        </ScrollViewer>
    </DockPanel>
</UserControl>