Question

What kind of panel should I use to put there two buttons – Next and Back for navigation? I want them to be in the last row in the center and with the stretching gap between – depending on the window size.

Answer 1

If you want a “stretching gap”, then I’d use a Grid

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="5*" />
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="*" />
        <ColumnDefinition Width="Auto" />
        <ColumnDefinition Width="5*" />
    </Grid.ColumnDefinitions>
    <Button Grid.Column="1" Content="Left" />
    <Button Grid.Column="3" Content="Right" />
</Grid>

You can adjust the size of your gap by adjusting the column definitions. The current definition will make the areas on the side of the buttons 5x whatever the gap is.