在窗口调整大小时更改数据网格列

有一个带分组的数据网格。但是，如果您运行该程序并调整窗口大小，则表格列的大小不会改变。可能此行为是由于分组中的 Expander 元素造成的。如何使表格列具有动态大小并在调整窗口大小时自动拉伸到全宽？

XML

<DataGrid ItemsSource="{Binding Items, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" SelectionMode="Extended" IsReadOnly="True" CanUserAddRows="False" CanUserDeleteRows="False"
            AutoGenerateColumns="False" ScrollViewer.HorizontalScrollBarVisibility="Disabled"
            ScrollViewer.CanContentScroll="True" ScrollViewer.VerticalScrollBarVisibility="Auto">
<DataGrid.GroupStyle>
  <!-- Style for groups at top level. -->
  <GroupStyle>
    <GroupStyle.ContainerStyle>
      <Style TargetType="{x:Type GroupItem}">
        <Setter Property="Margin" Value="0,0,0,5"/>
        <Setter Property="Template">
          <Setter.Value>
            <ControlTemplate TargetType="{x:Type GroupItem}">
              <Expander IsExpanded="true" Background="DarkGray" BorderBrush="DarkGray" Foreground="Black" BorderThickness="1,1,1,5">
                <Expander.Header>
                  <DockPanel>
                    <TextBlock FontWeight="Bold" Text="{Binding Path=Name}" Margin="5,0,0,0" Width="100"/>
                  </DockPanel>
                </Expander.Header>
                <Expander.Content>
                  <ItemsPresenter />
                </Expander.Content>
              </Expander>
            </ControlTemplate>
          </Setter.Value>
        </Setter>
      </Style>
    </GroupStyle.ContainerStyle>
  </GroupStyle>
</DataGrid.GroupStyle>
<DataGrid.Columns>
  <DataGridTextColumn Header="Name" Binding="{Binding Model.Name, Mode=OneWay}" Width="40*"/>
  <DataGridTemplateColumn Header="Added">
    <DataGridTemplateColumn.CellTemplate>
      <DataTemplate>
        <CheckBox IsChecked="{Binding Path=Model.Checked, UpdateSourceTrigger=PropertyChanged}" HorizontalAlignment="Center"/>
      </DataTemplate>
    </DataGridTemplateColumn.CellTemplate>
  </DataGridTemplateColumn>
</DataGrid.Columns>

查看模型

   public class MainViewModel
   {
      public MainViewModel()
      {
         _items.Add("Test", new List<MyModel>
         {
            new MyModel { Name ="val1", Checked = true},
            new MyModel { Name ="val2", Checked = false},
         });
         _items.Add("Test2", new List<MyModel>
         {
            new MyModel { Name ="val2", Checked = true},
            new MyModel { Name ="val4", Checked = false},
         });

         ItemsSource = new List<GridModel>();

         foreach (var item in _items)
         {
            foreach (var value in item.Value)
            {
               ItemsSource.Add(new GridModel { Group = item.Key, Model = value });
            }
         }
         _itemsCollectionView = CollectionViewSource.GetDefaultView(ItemsSource);
         var t = Items.CanGroup;
         _itemsCollectionView.GroupDescriptions.Add(new PropertyGroupDescription("Group"));
         _itemsCollectionView.Refresh();
      }

      private Dictionary<string, List<MyModel>> _items = new Dictionary<string, List<MyModel>>();
      public List<GridModel> ItemsSource { get; set; }

      private ICollectionView _itemsCollectionView;

      public ICollectionView Items
      {
         get { return _itemsCollectionView; }
         set { _itemsCollectionView = value; }
      }
   }

   public class GridModel
   {
      public string Group { get; set; }
      public MyModel Model { get; set; }
   }

   public class MyModel
   {
      public string Name { get; set; }
      public bool Checked { get; set; }
   }