WPF: DockPanel.Dock = "Bottom" doesn't work as expected

This concerns WPF.

As a simple test, I have a grid with 3 columns, the third column containing a Dock panel. In turn, this Dockpanel contains a TextBlock and a StatusBar, with the StatusBar having the (attached) attribute Dockpanel.Dock = "Bottom".

So I would expect the StatusBar to be at the bottom of the 3rd column, with the TextBlock - the one that says "I am TextBlock 3" - on top of it (within the same column).

To my surprise, however, the StatusBar appears on the RIGHT side of the TextBlock!

This is the relevant xaml-code (there is no code-behind made by me):

<Window x:Class="Testing.TestWindow"
        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:Testing"
        mc:Ignorable="d"
        Title="TestWindow" Height="500" Width="1000">

    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" MinWidth="180" MaxWidth="540"  />
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>

        <TextBlock Grid.Column="0">I am Textblock 1</TextBlock>

        <TextBlock Grid.Column="1">I am Textblock 2</TextBlock>

        <DockPanel Grid.Column="2">
            <TextBlock>I am Textblock 3</TextBlock>
            <StatusBar DockPanel.Dock="Bottom">I am the statusbar</StatusBar>
        </DockPanel>
    </Grid>

</Window>

Anyone know what I'm doing wrong? Thanks.

Solution

Update your DockPanel to have LastChildFill="False"

  <DockPanel Grid.Column="2" LastChildFill="false">

The property is true by default, and since the StatusBar is the LastChild of the DockPanel, you see the behavior you are experiencing.

LastChildFill info from docs:

true if the last child element stretches to fill the remaining space; otherwise false. The default value is true.