UserControl 中嵌套 DataGrid 中的 WPF SelectedItem 属性

I have UserControl，我们称其为CustomDataGrid，其中包含DataGrid。剩下的内容并不重要。SelectedItem的财产DataGrid必须是SelectedItem的财产CustomDataGrid。我希望能够使用Binding有了这个属性，因为我使用MVVM图案。所以我必须声明SelectedItem as DependencyProperty in CustomDataGrid。但我不知道如何才能正确地做到这一点......

就是这样DepedencyProperty-s 通常声明：

public static readonly DependencyProperty SelectedItemProperty = DependencyProperty.Register(
        "SelectedItem", typeof(Object), typeof(CustomDataGrid),
        new FrameworkPropertyMetadata(default(Object), SelectedItemPropertyCallback)
        {
            BindsTwoWayByDefault = true, 
            DefaultUpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged
        });

// Optionally
private static void SelectedItemPropertyCallback(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
    // dataGrid - `DataGrid` nested in `UserControl` 
    ((CustomDataGrid)obj).dataGrid.SelectedItem = e.NewValue;
}

// Obviously, it has no any link with nested `dataGrid`. This is the problem.  
public Object SelectedItem
{

    get { return GetValue(SelectedItemProperty); }
    set { SetValue(SelectedItemProperty, value); }
}

那么，我该如何声明SelectedItem属性正确吗？

您可以利用绑定框架将此类属性从底层对象连接到外部容器

示例假设CustomDataGrid as UserControl

        class CustomDataGrid : UserControl
        {
            public CustomDataGrid()
            {
                Binding b = new Binding("SelectedItem");
                b.Source = this;
                b.Mode = BindingMode.TwoWay;
                dataGrid.SetBinding(DataGrid.SelectedItemProperty, b);
            }

            public object SelectedItem
            {
                get { return (object)GetValue(SelectedItemProperty); }
                set { SetValue(SelectedItemProperty, value); }
            }

            // Using a DependencyProperty as the backing store for SelectedItem.  This enables animation, styling, binding, etc...
            public static readonly DependencyProperty SelectedItemProperty =
                DependencyProperty.Register("SelectedItem", typeof(object), typeof(CustomDataGrid), new PropertyMetadata(null));
        }

我创建了一个名为SelectedItem in CustomDataGrid并设置双向绑定SelectedItem实际的dataGrid inside.

因此这将连接这些属性并来回传播任何更改。