c# - 将 MenuItem 的 CommandParameter 绑定(bind)到父 DataGrid

Question

如何将命令参数从 MenuItem 绑定(bind)到父 Grid DataContext？

我有一个带有 ContextMenu 的 DataGrid，将菜单项绑定(bind)到 ViewModel 命令，但命令参数始终为 null。

我在 DataGrid 中使用 Tag 参数来访问 DataContext 并使用所需的命令，但我可以弄清楚从每一行获取绑定(bind)数据以用作命令参数。

我已经在这里查看了很多答案，但找不到任何有效的方法，ViewModel 中的命令参数被调用并且命令参数始终为 null。

C#

public class People
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class PeopleWindowViewModel
{
    public List<People> Peoples { get; set; }

    public PeopleWindowViewModel()
    {
        // populate Peoples list...
    }

    public ICommand RemoveCommand
    {
        get
        {
            return RelayCommand.Create((m) =>
            {
                // m always null
            });
        }
    }
}

public class PeoplePage : Page
{
    public PeoplePage()
    {
        InitializeComponent();

        DataContext = new PeopleWindowViewModel();
    }
}

XAML:

  <DataGrid
      Margin="0 8 0 8"
      d:DataContext="{d:DesignInstance local:People}"
      IsReadOnly="True"
      ItemsSource="{Binding Peoples}"
      Tag="{Binding DataContext,
                      RelativeSource={RelativeSource AncestorType={x:Type Page}}}">
    <DataGrid.Columns>
      <DataGridTextColumn
          Binding="{Binding Id}"
          Header="Id" />
      <DataGridTextColumn
          Binding="{Binding Name}"
          Header="Name" />
    </DataGrid.Columns>

    <DataGrid.ContextMenu>
      <ContextMenu
          Tag="{Binding Path=PlacementTarget.Tag,
                              RelativeSource={RelativeSource Self}}">
        <MenuItem
            Command="{Binding PlacementTarget.Tag.RemoveCommand,
                                      RelativeSource={RelativeSource Mode=FindAncestor,
                                                                     AncestorType=ContextMenu}}"
            CommandParameter="{Binding Path=Id,
                                               RelativeSource={RelativeSource Mode=FindAncestor,
                                                                              AncestorType=DataGrid}}"
            Header="Remover" />
      </ContextMenu>
    </DataGrid.ContextMenu>
  </DataGrid>
</Page>

Answer 1

我找到了解决方案，但不确定是否有更好的解决方案。不管怎样，你可以这样做:

<DataGrid ItemsSource="{Binding Peoples}">
    <DataGrid.Resources>
        <ContextMenu x:Key="ctx_menu">
            <ContextMenu.Resources>
                <Style TargetType="{x:Type MenuItem}">
                    <Setter Property="DataContext" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}" />
                </Style>
            </ContextMenu.Resources>
            <MenuItem Command="{Binding DataContext.RemoveCommand}"
                      CommandParameter="{Binding PlacementTarget.DataContext, RelativeSource={RelativeSource AncestorType={x:Type ContextMenu}}}"
                      Header="Remove" />
        </ContextMenu>
    </DataGrid.Resources>

    <DataGrid.ItemContainerStyle>
        <Style TargetType="{x:Type DataGridRow}">
            <Setter Property="ContextMenu" Value="{StaticResource ctx_menu}" />
        </Style>
    </DataGrid.ItemContainerStyle>

</DataGrid>

编辑:这会为您提供整个 People 对象作为 CommandParameter。如果您只想要 Id，只需将 CommandParameter 更改为:

CommandParameter="{Binding PlacementTarget.DataContext.Id, RelativeSource={RelativeSource AncestorType={x:Type ContextMenu}}}"