MVVM 树状 View 选定项

Question

我希望有人愿意在这里帮助我。
我对 MVVM 很陌生，在阅读了许多帖子和示例之后，我仍然无法弄清楚这一点。

我有 EF 数据库填充属于每个项目的项目和计算。
我正在使用 TreeView 和 HierarchicalDataTemplate 显示项目和计算。
当我单击 TreeView 项目时，我想绑定(bind)要设置的标签文本

public string totaalPrijs

但我就是不知道该怎么做!

这就是我的 CalculationViewModel 的样子

namespace Treeview_test1.ViewModel
{
public class CalculationViewModel : ViewModelBase
{
    public CalculationViewModel(TableItemChildren child)
    {
        this.Child = child;
        IsChecked = false;
    }

    public TableItemChildren Child { get; protected set; }

    public string totaalPrijs
    {
        get { return Child.dbTotaalPrijs; }
        set
        {
            if (Child.dbTotaalPrijs != value)
            {
                Child.dbTotaalPrijs = value;
                RaisePropertyChanged("totaalPrijs");
            }
        }
    }

    private bool _isChecked;
    public bool IsChecked
    {
        get { return _isChecked; }
        set
        {
            if (_isChecked != value)
            {
                _isChecked = value;
                RaisePropertyChanged("IsChecked");
            }
        }
    }

}

这是我的 ItemViewModel

namespace Treeview_test1.ViewModel
{
public class ItemViewModel : ViewModelBase
{
    public ItemViewModel()
    {
        calcVMColl = new ObservableCollection<CalculationViewModel>();
        foreach (TableItemChildren calc in Service.getItemCalculations("1"))
        {
            calcVMColl.Add(new CalculationViewModel(calc));
        }
    }

    // Switch between real and mock data
    private IGetCalculations _service;
    public IGetCalculations Service
    {
        get
        {
            if (_service == null)
            {
                if (IsInDesignMode)
                    _service = new MockCalculations();
                else
                    _service = new GetCalculations();
            }
            return _service;
        }
        set
        {
            _service = value;
        }
    }

    private ObservableCollection<CalculationViewModel> _calcVMColl;
    public ObservableCollection<CalculationViewModel> calcVMColl
    {
        get { return _calcVMColl; }
        set
        {
            if (calcVMColl != value)
            {
                _calcVMColl = value;
                RaisePropertyChanged("calcVMColl");
            }
        }
    }
}

和 XAML

<Window x:Class="Treeview_test1.MainWindow" xmlns="http://schemas.microsoft.com/   winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525" xmlns:ViewModel="clr-namespace:Treeview_test1.ViewModel">
<Window.DataContext>
    <ViewModel:ItemViewModel />
</Window.DataContext>
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="204" />
        <ColumnDefinition />
    </Grid.ColumnDefinitions>
    <TreeView x:Name="tree" Width="195" HorizontalAlignment="Left" ItemsSource="{Binding calcVMColl}" Background="LightGray" Grid.Column="0" RenderTransformOrigin="1.016,0.509">
        <TreeView.ItemContainerStyle>
            <Style TargetType="{x:Type TreeViewItem}">
                <Setter Property="IsSelected" Value="{Binding IsChecked, Mode=TwoWay}" />
                <Style.Triggers>
                    <Trigger Property="IsSelected" Value="True">
                        <Setter Property="FontSize" Value="10" />
                    </Trigger>
                </Style.Triggers>
            </Style>
        </TreeView.ItemContainerStyle>
        <TreeView.Resources>
            <DataTemplate DataType="{x:Type ViewModel:CalculationViewModel}">
                <Label Content="{Binding totaalPrijs}" />
            </DataTemplate>
        </TreeView.Resources>
    </TreeView>
    <Label Grid.Column="1" HorizontalAlignment="Left" Margin="39,39,0,0" VerticalAlignment="Top" Content="{Binding....?}" Foreground="Black" FontFamily="segeo ui" FontSize="20" />
</Grid>

简而言之:如何将我的标签文本绑定(bind)到当前选定的 TreeView 项？

提前致谢

艾迪

Answer 1

绑定(bind)SelectedItem的 TreeView到 Label (或 TextBlock )相当简单:

<TreeView Name="myTreeview"/>
<TextBlock Text="{Binding SelectedItem, ElementName=myTreeview, Mode=OneWay}"/>

但是，这实际上不会显示您想要的，因为 SelectedItem的 TreeView通常是 Object你需要一个 string显示在 TextBlock .

处理此问题的一种方法是使用 Converter装订上。你可以实现 IValueConverter并让它从 SelectedItem 返回所需的字符串.

   class GetTextFromItemConverter : IValueConverter
   {
      object IValueConverter.Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
      {
         TreeViewItem itm = (TreeViewItem)value;
         string myString = null;
         //Retrieve whatever portion of the TreeViewItem you want to put in myString.
         return myString;
      }

      object IValueConverter.ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
      {
         throw new NotImplementedException();
      }
   }

然后绑定(bind)你的 TextBlock看起来像这样:

<TextBlock Text="{Binding SelectedItem, Converter={StaticResource GetTextFromItemConverter}, ElementName=myTreeview, Mode=OneWay}"/>