如何获取绑定真实的根级绑定源？MVVM

Question

在View里

        [Import]
        MaterialCategorysViewModel ViewModel
        {
            set 
            {
                this.DataContext = value;
            }
        }

在view里我有一个Tab控件：

 <TabControl Grid.Row="1"  Name="tabControl1" SelectedIndex="{Binding SelectedTabIndex}">
                <TabItem Header="概览" >
                    <!--local:MaterialCategoryListView DataContext="{Binding}"/-->
                    <TreeView Name="CategoryTreeView" ItemsSource="{Binding Path=Model}"  
                     ItemTemplate ="{StaticResource NavigationTemplate }" >
                        <TreeView.ItemContainerStyle>
                            <!-- This Style binds a TreeViewItem to a PersonViewModel.  -->
                            <Style TargetType="{x:Type TreeViewItem}">
                                <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}" />
                                <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" />
                                <Setter Property="FontWeight" Value="Normal" />
                                <Style.Triggers>
                                    <Trigger Property="IsSelected" Value="True">
                                        <Setter Property="FontWeight" Value="Bold" />
                                    </Trigger>
                                </Style.Triggers>
                            </Style>
                        </TreeView.ItemContainerStyle>
                
                    </TreeView>
                </TabItem>
                <TabItem Header="基本" Name="tabItem1" DataContext="{Binding ElementName=CategoryTreeView, Path=SelectedItem}">
                     <Grid >
                        <Grid.RowDefinitions>
                            <RowDefinition Height="Auto" />
                            <RowDefinition Height="Auto" />
                            <RowDefinition Height="Auto" />
                            <RowDefinition Height="45*" />
                            <RowDefinition Height="387*" />
                        </Grid.RowDefinitions>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="52" />
                            <ColumnDefinition Width="265" />
                            <ColumnDefinition Width="117" />
                            <ColumnDefinition Width="Auto" />
                            <ColumnDefinition Width="51" />
                            <ColumnDefinition Width="115*" />
                        </Grid.ColumnDefinitions>
                        <Label Content="名称:" Height="28" HorizontalAlignment="Left" Margin="12,6,0,0" Name="label1" VerticalAlignment="Top" />
                        <Label Content="描述:" Grid.Row="1" Height="28" HorizontalAlignment="Left" Margin="12,5,0,0" Name="label2" VerticalAlignment="Top" />
                        <TextBox Grid.Column="1" 
                 Name="textBoxName"
                 Height="23" 
                 HorizontalAlignment="Left"
                 Margin="9,8,0,0"
                 VerticalAlignment="Top" Width="250" 
                 Text="{jas:FocusBinding Path=Name, ValidatesOnDataErrors=True}"
                 >
                            <i:Interaction.Behaviors>
                                <behaviors:FocusBehavior></behaviors:FocusBehavior>
                            </i:Interaction.Behaviors>
                        </TextBox>


                        <TextBox Grid.Column="1" 
                 Grid.Row="1" 
                 Height="23" 
                 HorizontalAlignment="Left" 
                 Margin="9,7,0,0" 
                 Name="textBox2" 
                 VerticalAlignment="Top" 
                 Width="365" Grid.ColumnSpan="2" 
                 Text="{Binding Path=Description}"/>
                        <csla:PropertyStatus Grid.Column="2" Margin="11,11,86,3" Name="propertyStatus1" Width="20" Height="20" Property="{Binding Path=Name }" />
                        <csla:PropertyStatus Grid.Column="4" Grid.Row="1" Margin="12,7,19,7" Name="propertyStatus2" Width="20" Height="20" Property="{Binding Path=Description}" />

                    </Grid>
                </TabItem>
            </TabControl>

如何从 text控件 textBoxName可以获取绑定的 this.DataContext = value;既ViewModel?

Answer 1

是俺的问题描述不够清楚吗？

 

Answer 2

别急，论坛上是不是实时都能回复的。我们需要点时间来看下，不过今天肯定我会给你一个回复的。

---

Bob Bao [MSFT]
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Answer 3

Ok, 看来你使用了MEF，而且你里面还有一个 custom markup extension {jas:FocusBinding }. 当然对于这个markup extension 我肯定不是很了解，如果你觉得这个问题和这个相关的话，最好是提供下这些的具体信息。

不过你的问题是如何 当前 View 的 DataContext. 如果与MEF和上述markup extension无关的话，简单的做法就是：假如说你的View是一个 UserControl 类型的，你就可以用RelativeSource去找到这个View实例，然后设置这个TextBox的DataContext.

    <TextBox Grid.Column="1" 
             Name="textBoxName"
             Height="23" 
             HorizontalAlignment="Left"
             Margin="9,8,0,0"
             VerticalAlignment="Top" Width="250" 
             Text="{jas:FocusBinding Path=Name, ValidatesOnDataErrors=True}"
             DataContext="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type UserCotnrol}}, Path=DataContext}">
      <i:Interaction.Behaviors>
        <behaviors:FocusBehavior></behaviors:FocusBehavior>
      </i:Interaction.Behaviors>
    </TextBox>

Sincerely,

---

Bob Bao [MSFT]
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Answer 4

谢谢，Bobo

{jas:FocusBinding } 在这里是个关键。 我需要在ViewModel控制View里的控件的Focus. Jas:FocusBinding可以参考http://joshsmithonwpf.wordpress.com/2010/03/16/control-input-focus-from-viewmodel-objects/

现在的问题是这样的。我在ViewModel里继承了这个扩展的IFocusMover接口：

 public class MaterialCategorysViewModel:ViewModel<MaterialCategorys>,IFocusMover

在View里，我用TreeView来绑定MaterialCategorys. 然后用下面的表达式来绑定Treeview里的选定的行"{Binding ElementName=CategoryTreeView, Path=SelectedItem}"> 。

然后再绑定到这个行里的列,如Text="{jas:FocusBinding Path=Name, ValidatesOnDataErrors=True}".

Focusbinding这个扩展：

 

public class FocusBinding : BindingDecoratorBase
    {
        public override object ProvideValue(IServiceProvider provider)
        {
            DependencyObject elem;
            DependencyProperty prop;
            if (base.TryGetTargetItems(provider, out elem, out prop))
            {
                FocusController.SetFocusableProperty(elem, prop);
            }

            return base.ProvideValue(provider);
        }
    }

这个扩展会获取textName以及我绑定的属性Text。 在这个扩展里，他通过：element.GetValue(FrameworkElement.DataContextProperty)获取这个控件的DataContextProperty. 如果对于这个控件是直接绑定到Usercontrol的Datacontext

的，就相当于直接绑定到了ViewModel。但是对于我的情况不一样，我的TextBox是绑定到TreeView的SelectedItem。 TreeView是绑定到Model。 Model是属于ViewModel

里的一个属性： public static readonly DependencyProperty ModelProperty;

儿现在用到这个:element.GetValue(FrameworkElement.DataContextProperty)。获取的只是一个Collection。而不是ViewModel. 所以我的问题是如何才能获取真实的绑定源头啊？

MaterialCategorysViewModel=>Model=>SelectedItem=>Name。 就是从Name怎么能够获取MaterialCategorysViewModel(ViewModel)这个绑定？

 

static void CreateHandler(DependencyObject elemnt, DependencyProperty property)
        {
            var focusMover = element.GetValue(FrameworkElement.DataContextProperty) as IFocusMover;
            if (focusMover == null)
            {
                var handler = element.GetValue(MoveFocusSinkProperty) as MoveFocusSink;
                if (handler != null)
                {
                    handler.ReleaseReferences();
                    element.ClearValue(MoveFocusSinkProperty);
                }
            }
            else
            {
                var handler = new MoveFocusSink(element as UIElement, property);
                focusMover.MoveFocus += handler.HandleMoveFocus;
                element.SetValue(MoveFocusSinkProperty, handler);
            }
        }

 

Answer 5

额，看了你的描述，我觉得我的那个代码是可以解决你的问题的，通过RelativeSource把跟元素的DataContext引导到当前TextBox里来。你试一下。

---

Bob Bao [MSFT]
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Answer 6

我没有用到Datacontext.

 [Import]
        MaterialCategorysViewModel ViewModel
        {
            set
            {
                var src = (System.Windows.Data.CollectionViewSource)(this.FindResource("MaterialCategorysViewModelSource"));
                src.Source = new List<object> { value };
                
            }
        }

在父窗体用到的是：

  <ad:DockableContent.Resources >
        <CollectionViewSource x:Key="MaterialCategorysViewModelSource"/>

    </ad:DockableContent.Resources>

我如何访问这个CollectionViewSource ？

Answer 7

那你就可以用 StaticResoruce 来设置 TextBox的DataContext了：

    <TextBox DataContext="{Binding Source={StaticResource MaterialCategorysViewModelSource}}" .../>

---

Bob Bao [MSFT]
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Get or Request Code Sample from Microsoft
Please remember to mark the replies as answers if they help and unmark them if they provide no help.

Answer 8

DataContext="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type UserCotnrol}}, Path=DataContext}"

这个可以了，不过必须加上:,AncestorLevel=2。 因为我是UserControl里含有UserControl.