Make ScrollViewer fill dynamic area - wpf

Question

In the example below I cannot get the ScrollViewer to fill the space available, The height is unknown due to the dynamic content above but is there no way it can fill the space available instead of over running?
<Grid x:Name="Main" Height="200" MaxHeight="200">
<StackPanel>
<Grid x:Name="MainContent" Height="170" MaxHeight="170">
<StackPanel>
<TextBlock FontSize="24" Text="Dynamic data "/>
<TextBlock FontSize="24" Text="height "/>
<TextBlock FontSize="24" Text="unknown... "/>
<Grid x:Name="Results" Background="Red">
<ScrollViewer>
<StackPanel>
<TextBlock FontSize="24" Text="Result set... 0"/>
<TextBlock FontSize="24" Text="Result set... 1"/>
<TextBlock FontSize="24" Text="Result set... 2"/>
<TextBlock FontSize="24" Text="Result set... 3"/>
</StackPanel>
</ScrollViewer>
</Grid>
</StackPanel>
</Grid>
<Grid x:Name="Nav">
<Button HorizontalAlignment="Left" Content="Back"/>
<Button HorizontalAlignment="Right" Content="Forward"/>
</Grid>
</StackPanel>
</Grid>

Answer 1

in MainContent Grid use DockPanel instead of StackPanel with LastChildFill=True, something like this:
<Grid x:Name="MainContent" Height="170" MaxHeight="170">
<DockPanel LastChildFill="True">
<TextBlock DockPanel.Dock="Top" FontSize="24" Text="Dynamic data "/>
<TextBlock DockPanel.Dock="Top" FontSize="24" Text="height "/>
<TextBlock DockPanel.Dock="Top" FontSize="24" Text="unknown... "/>
<Grid x:Name="Results" Background="Red">
<ScrollViewer>
<StackPanel>
<TextBlock FontSize="24" Text="Result set... 0"/>
<TextBlock FontSize="24" Text="Result set... 1"/>
<TextBlock FontSize="24" Text="Result set... 2"/>
<TextBlock FontSize="24" Text="Result set... 3"/>
</StackPanel>
</ScrollViewer>
</Grid>
</DockPanel>
</Grid>
then last element of DockPanel will adjust itself to available space

Answer 2

I solved it by adding another element for the Scrollviewer's Height to bind:
<grid Grid.row="3" x:Name="Mirror">
</grid>
<ScrollViewer Grid.row="3" Height="{Binding ElementName=uxMirror,XPath=ActualHeight}">
</ScrollViewer>

Answer 3

Firstly your layout is kind of a mess. Why do you need to put a StackPanel as the only child of a Grid. For the Rows? Use RowDefinitions and ColumnDefinitions when dealing with Grid
From my understanding of your layout, you can pretty much do everything you need with just a Grid and a DockPanel. When dealing with layout containers, Aim to get your layout with the "least" number of containers as "efficiently" possible. Even if it aint any real performance benefit, it helps enormously when going through someone else's code to not have redundant nesting
<Grid x:Name="Main">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBlock Grid.Row="0"
FontSize="24"
Text="Dynamic data " />
<TextBlock Grid.Row="1"
FontSize="24"
Text="height " />
<TextBlock Grid.Row="2"
FontSize="24"
Text="unknown... " />
<ScrollViewer Grid.Row="3"
Background="Red">
<StackPanel>
<TextBlock FontSize="24"
Text="Result set... 0" />
<TextBlock FontSize="24"
Text="Result set... 1" />
<TextBlock FontSize="24"
Text="Result set... 2" />
<TextBlock FontSize="24"
Text="Result set... 3" />
</StackPanel>
</ScrollViewer>
<DockPanel x:Name="Nav"
Grid.Row="4"
LastChildFill="False">
<Button Content="Back"
DockPanel.Dock="Left" />
<Button Content="Forward"
DockPanel.Dock="Right" />
</DockPanel>
</Grid>
This should give you everything your looking for. If you need to restrict Height dimensions with static values, Add them in accordingly when absolutely needed.
As for the "Nav" DockPanel, yes you can using HorizontalAlignment get your Button's positioned Left and Right and thereby not use the DockPanel, but that would go against the concept of trying to keep "one" item in a Grid cell and hence the DockPanel usage.