<Grid>
  <Grid.RowDefinitions>
    <RowDefinition Height="10*"/>
    ...
  </Grid.RowDefinitions>
  <Grid.ColumnDefinitions>
     <ColumnDefinition Width="2*"/>
     ...
  </Grid.ColumnDefinitions>
  <Label Grid.Column="0" Grid.Row="0">Civilité</Label>
  <ComboBox Grid.Column="1" Grid.Row="0"/>
  ...
  <Label Grid.Column="2" Grid.Row="5">Commune</Label>
  <TextBox Grid.Column="3" Grid.Row="5"/>
  <!-- I'd like to put the ListBox under this TextBox -->
</Grid>