How can I make a column in a listbox in WPF the same width for all items?

Question

I have a ListBox with an ItemTemplate consisting of a TextBlock and a ComboBox. The problem is that the width of the text inside the TextBlock is not the same for each item and the ComboBox controls are not aligned.
How can I set the TextBlock in the template so all items are the same width, that is the one of the widest?

Here is my xaml:

<ListBox MinHeight="100" ItemsSource="{Binding Trainees}">
  <ListBox.ItemTemplate>
    <DataTemplate>
      <Grid Margin="1">
        <Grid.ColumnDefinitions>
          <ColumnDefinition />
          <ColumnDefinition />
        </Grid.ColumnDefinitions>
        <TextBlock VerticalAlignment="Center" Grid.Column="0">
          <TextBlock.Text>
            <MultiBinding StringFormat="{}{0}, {1}">
              <Binding Path="LastName" />
              <Binding Path="FirstName" />
            </MultiBinding>
          </TextBlock.Text>
        </TextBlock>
        <ComboBox HorizontalAlignment="Left" Grid.Column="1"
            ItemsSource="{Binding Source={StaticResource Functions}}" SelectedValue="{Binding Path=Function}"
            MinWidth="100" />
      </Grid>
    </DataTemplate>
  </ListBox.ItemTemplate>
</ListBox>

Answer 1

You can use the IsSharedSizeScope attached property. In your template definition, attach a "shared size group" to each column, like this:

<Grid.ColumnDefinitions>
    <ColumnDefinition SharedSizeGroup="col1" />
    <ColumnDefinition SharedSizeGroup="col2" />
</Grid.ColumnDefinitions>

... then define your ListBox as a shared size scope so it knows to size each "size group" the same way:

<ListBox Grid.IsSharedSizeScope="True">...</ListBox>