Question: I am using a RichTextBox in WPF, and am trying to set the default paragraph spacing to 0 (so that there is no paragraph spacing). While I could do this in XAML, I would like to achieve it programmatically if possible. Any ideas?

Answer: 
I did it **with style** (pun indented)

```
<RichTextBox  Margin="0,51,0,0" Name="mainTextBox" >
        <RichTextBox.Resources>
            <Style TargetType="{x:Type Paragraph}">
                <Setter Property="Margin" Value="0"/>
            </Style>
        </RichTextBox.Resources>
    </RichTextBox>

```
For me on VS2017 in WPF works this:

```
 <RichTextBox HorizontalAlignment="Left" Height="126" Margin="10,280,0,0" VerticalAlignment="Top" Width="343" FontSize="14" Block.LineHeight="2"/>

```

The key is **Block.LineHeight="2"**

You can found this also in Properties view but you can't change below 6px from there.