WPF: LineBreak enable/disable dynamically - wpf

Question

i would like to make the LineBreak element inside of that TextBlock controllable by the user in preferences to Enable/Disable it being there
<TextBlock Style="{StaticResource TextBlockStyle}" Width="130">
<TextBlock.Inlines>
<Run Text="{Binding Path=Name}" FontWeight="Bold" Foreground="#FF2A4D9E" />
<Run Text="{Binding Path=Price}" FontWeight="Bold" />
<LineBreak />
<Run Text="{Binding Path=Quantity}" Foreground="#99000000" />
</TextBlock.Inlines>
</TextBlock>

Answer 1

I don't believe there is any way in a FlowDocument to make a LineBreak not really break except to take it out. Your choices are to switch to using WPF layout or to use an attached property to switch between a LineBreak and an empty Run.
Using WPF layout
You may consider using WPF layout instead. Something like this:
<DataTemplate x:Key="Layout1">
<DockPanel>
<TextBlock Text="{Binding Name}" FontWeight="Bold" Foreground="#FF2A4D9E" />
<TextBlock Text="{Binding Price}" FontWeight="Bold" />
<TextBlock Text="{Binding Quantity}" Foreground="#99000000" />
</DockPanel>
</DataTemplate>
<DataTemplate x:Key="Layout2">
<DockPanel>
<DockPanel DockPanel.Dock="Top">
<TextBlock Text="{Binding Name}" FontWeight="Bold" Foreground="#FF2A4D9E" />
<TextBlock Text="{Binding Price}" FontWeight="Bold" />
</DockPanel>
<TextBlock Text="{Binding Quantity}" Foreground="#99000000" />
</DockPanel>
</DataTemplate>
Now you can easily switch between layouts just by switching DataTemplates.
Automatically removing LineBreaks using bindings
If you want to "hide" the LineBreak via a binding you can do it with an attached "BecomeLineBreak" property that, when applied to an empty Run and set true, removes it and replaces it with a LineBreak.
Like magic you now have the ability to write:
<Run my:LineBreakSwitcher.BecomeLineBreak="{Binding SomeCondition}" />
And your Run will turn into a LineBreak any time the SomeCondition property is true.
Here is the code:
public class LineBreakSwitcher : DependencyObject
{
public static bool GetBecomeLineBreak(DependencyObject obj) { return (bool)obj.GetValue(BecomeLineBreakProperty); }
public static void SetBecomeLineBreak(DependencyObject obj, bool value) { obj.SetValue(BecomeLineBreakProperty, value); }
public static readonly DependencyProperty BecomeLineBreakProperty = DependencyProperty.RegisterAttached("BecomeLineBreak", typeof(bool), typeof(LineBreakSwitcher), new PropertyMetadata
{
PropertyChangedCallback = (obj, e) =>
{
var oldElement = (Inline)obj;
var newElement = (bool)e.NewValue ? (Inline)new LineBreak() : new Run();
newElement.SetBinding(BecomeLineBreakProperty, oldElement.GetBindingExpression(BecomeLineBreakProperty).ParentBindingBase);
var parent = (Paragraph)oldElement.Parent;
parent.Inlines.InsertBefore(oldElement, newElement);
parent.Inlines.Remove(oldElement);
}
});
How it works: When BecomeLineBreak becomes true on a Run, a new LineBreak is created, the BecomeLineBreak binding is copied across, the LineBreak is inserted before the Run, then the Run is removed. When BecomeLineBreak become false, a new Run is created and the whole process happens in reverse.

Answer 2

This is what you want (100% XAML):
<TextBlock Text="{Binding Text, ElementName=MyContainer}"
FontWeight="Bold" FontSize="14" Name="TextBlockA" />
<TextBlock Name="TextBlockB">
<TextBlock.Style>
<Style>
<Setter Property="TextBlock.Visibility" Value="Visible"/>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Text.Length,
ElementName=TextBlockC}" Value="0">
<Setter Property="TextBlock.Visibility" Value="Collapsed"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
<LineBreak />
</TextBlock>
<TextBlock Text="{Binding SubText, ElementName=MyContainer}"
FontWeight="Normal" FontSize="12" Name="TextBlockC" />