使用MVVM,如何将XamDataGrid的SelectedItems作为参数传递给ContextMenu引发的Command？

Question

我正在尝试在XamDataGrid上传递项目,我右键单击鼠标右键以打开ContextMenu,它在我的ViewModel中引发了一个Command.不知何故,Command调用的方法在调试模式下无法访问.

这是从视图中剪断的

<ig:XamDataGrid DataSource="{Binding DrdResults}" Height="700" Width="600">
  <ig:XamDataGrid.ContextMenu>
    <ContextMenu DataContext="{Binding RelativeSource={RelativeSource Mode=Self},
                               Path=PlacementTarget.DataContext}"
                 AllowDrop="True" Name="cmAudit">
      <MenuItem Header="View History" 
                Command="{Binding ViewTradeHistory}"
                CommandParameter="{Binding Path=SelectedItems}">
      </MenuItem>
    </ContextMenu>
  </ig:XamDataGrid.ContextMenu>
  <ig:XamDataGrid.FieldSettings>
    <ig:FieldSettings AllowFixing="NearOrFar"
                      AllowEdit="False" 
                      Width="auto" Height="auto"  />
  </ig:XamDataGrid.FieldSettings>
</ig:XamDataGrid>

此View的相应ViewModel中的代码如下所示.

public WPF.ICommand ViewTradeHistory
{
  get
  {
    if (_viewTradeHistory == null)
    {
      _viewTradeHistory = new DelegateCommand(
      (object SelectedItems) =>
      {
        this.OpenTradeHistory(SelectedItems); 
      });
    }
    return _viewTradeHistory;
  }
}

最后,命令调用的实际方法如下所示

private void OpenTradeHistory(object records)
{
  DataPresenterBase.SelectedItemHolder auditRecords
    = (DataPresenterBase.SelectedItemHolder)records;
  // Do something with the auditRecords now.
}

我不确定我在这里做错了什么.任何帮助将非常感谢.

谢谢,Shravan

Answer 1

我通过改进达米安的答案(这不是很有效)来做到这一点.

这是我的解决方案:

首先是行为:

public class DataGridExtender : Behavior<XamDataGrid>
{
    public readonly static DependencyProperty SelectedDataItemsProperty
        = DependencyProperty.Register(
            "SelectedDataItems",
            typeof(ICollection<object>),
            typeof(DataGridExtender),
            new PropertyMetadata());

    public ICollection<object> SelectedDataItems
    {
        get { return (ICollection<object>)GetValue(SelectedDataItemsProperty); }
        set { SetValue(SelectedDataItemsProperty, value); }
    }

    protected override void OnAttached()
    {
        base.OnAttached();
        AssociatedObject.SelectedItemsChanged += AssociatedObjectOnSelectedItemsChanged;
        AssociatedObjectOnSelectedItemsChanged(AssociatedObject, null);
    }

    protected override void OnDetaching()
    {
        AssociatedObject.SelectedItemsChanged -= AssociatedObjectOnSelectedItemsChanged;
        base.OnDetaching();
    }

    private void AssociatedObjectOnSelectedItemsChanged(object sender, Infragistics.Windows.DataPresenter.Events.SelectedItemsChangedEventArgs e)
    {
        if (SelectedDataItems != null)
        {
            SelectedDataItems.Clear();
            foreach (var selectedDataItem in GetSelectedDataItems())
            {
                SelectedDataItems.Add(selectedDataItem);
            }
        }
    }

    private IEnumerable<object> GetSelectedDataItems()
    {
        var selectedItems = from rec in AssociatedObject.SelectedItems.Records.OfType<DataRecord>() select rec.DataItem;
        return selectedItems.ToList().AsReadOnly();
    }
}

然后它的用法:

<igDP:XamDataGrid>
[...]

<i:Interaction.Behaviors>
    <Behaviours:DataGridExtender SelectedDataItems="{Binding SelectedDataItems, Mode=TwoWay}"></Behaviours:DataGridExtender>
</i:Interaction.Behaviors>

[...]

<igDP:XamDataGrid.FieldLayoutSettings>
    [...]
</igDP:XamDataGrid.FieldLayoutSettings>

<igDP:XamDataGrid.FieldLayouts>
    <igDP:FieldLayout>
        [...]
    </igDP:FieldLayout>
</igDP:XamDataGrid.FieldLayouts>

当然,您需要在视图模型中使用"SelectedDataItems".

编辑:SelectedDataItems视图模型中的属性必须首先作为空集合进行快速计算,否则将无法正常工作.

Answer 2

对于单个项目,infragistics非常友好地添加一个名为"ActiveDataItem"的可绑定DependencyProperty,它是"所选项目"(如果有).它甚至可以双向工作,即您可以从ViewModel中重置选择.

不幸的是,AFAIK对于多选没有类似的东西.你必须自己实现这个,迭代选定的记录,检查它们是否是datarecords,获取记录和dataitem等...

Answer 3

尝试将 DataGrid 的 SelectedItem 绑定到视图模型中的属性。

然后您可以在您的方法中访问该属性OpenTradeHistory()。