当绑定到ViewModel属性时，WPF用户控件依赖项属性无法工作
我有两个用户控件:一个LocationTreeView和一个LocationPicker。LocationTreeView将位置组织到树结构中。由于所涉及的位置数，一次只加载树的一部分(一次加载一个级别，然后展开项)。
LocationPicker只不过是一个带有按钮的文本块，该按钮打开了一个带有LocationTreeView的模态窗口。
当我将LocationPicker的"SelectedLocation“属性绑定到我的视图模型时，它工作得很好。当我将我的LocationTreeView绑定到视图模型时，绑定似乎没有任何效果。当我将我的LocationTreeView绑定到一个“虚拟”LocationPicker (它绑定到我的视图模型)时，它可以工作。如何使我的LocationTreeView绑定到我的视图模型？
public partial class LocationTreeView: UserControl
{
public EventHandler LocationChanged;
...
public static readonly DependencyProperty SelectedLocationProperty =
DependencyProperty.Register("SelectedLocation",typeof(Location), typeof(LocationTreeView),
new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, SelectedLocationChanged));
...
public static void SelectedLocationChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
LocationTreeView sender = (d as LocationTreeView);
Location loc = e.NewValue as Location;
//Navigate the treeview to the selected location
sender.LoadLTreeViewPathToLocation(loc);
}
public Location SelectedLocation
{
get { return (Location)GetValue(SelectedLocationProperty); }
set
{
if (SelectedLocation != value)
{
SetValue(SelectedLocationProperty, value);
if (LocationChanged != null)
{
LocationChanged(this, EventArgs.Empty);
}
}
}
}
...
}绑定此控件时，绑定到另一个控件时工作良好，但绑定到我的视图模型时不起作用。我在SelectedLocationChanged回调中设置了一个断点，当我设置viewmodel属性(它确实实现了INotifyPropertyChanged)时，它似乎不会被触发。
public partial class LocationPicker: UserControl
{
public static readonly DependencyProperty SelectedLocationProperty =
DependencyProperty.Register("SelectedLocation",typeof(Location), typeof(LocationPicker),
new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
...
public Location SelectedLocation
{
get { return (Location)GetValue(SelectedLocationProperty); }
set { SetValue(SelectedLocationProperty, value); }
}
...
private void Button_Click(object sender, RoutedEventArgs e)
{
// create a window with a locationtreeview on it. Set the treeview's
// selectedlocation property, open the window, wait for the window to close,
// set this.SelectedLoctation to the treeview's selected location.
}
}我很抱歉遗漏了这么多代码。我的工作环境使我无法复制/粘贴。
我遗漏了ViewModel的代码。我深信这不是问题所在。
更新: LocationTreeView有一个在xaml中设置的ViewModel
<UserControl.DataContext>
<VM:LocationTreeViewViewModel />
</UserControl.DataContext>LocationPicker没有ViewModel。在我使用控件的窗口上，xaml看起来如下所示
<Widow.DataContext>
<VM:TestWindowViewModel />
</Window.DataContext>
<Grid>
...
<UC:LocationPicker x:Name="picker" SelectedLocation="{Binding Location}" />
<!-- this does not work -->
<UC:LocationTreeView SelectedLocaiton="{Binding Location}" />
<!-- but this works --->
<UC:LocationTreeView SelectedLocaiton="{Binding SelectedLocation, ElementName=picker}" />
...
</Grid>回答 1
Stack Overflow用户
发布于 2014-08-19 08:06:56
如果希望将数据绑定从视图模型绑定到LocationTreeView，则应使用要绑定到的视图模型中的属性。如果视图模型中有一个名为SelectedLocationInViewModel的属性，那么您应该使用它来绑定到：
<UC:LocationTreeView SelectedLocation="{Binding SelectedLocationInViewModel}" />我想我知道你现在有什么问题了.您希望在UserControl中定义一些属性并将数据绑定到它们，但也希望将数据绑定到设置为DataContext的视图模型中的属性。你需要用RelativeSource Binding来做.只需查看以下示例中的Binding Path：
将数据绑定到UserControl中从UserControl中声明的属性
<ItemsControl ItemsSource="{Binding PropertyName, RelativeSource={RelativeSource
AncestorType={x:Type YourPrefix:YourUserControl}}}" />将数据绑定到在任何对象集中声明为DataContext的属性
<ItemsControl ItemsSource="{Binding PropertyName}" />https://stackoverflow.com/questions/25371904
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