ItemsSource 到 TreeView 的 SelectedItem 的 属性

Question

我正在创建我的第一个 WPF 应用程序（之前用 WinForms 做过一些），我开始喜欢它了（即使它有时会增加不必要的复杂性..）。 但是我遇到了一个我无法真正弄清楚的问题。

问题： 我有一个 TreeView 和一个带有所选（第二级）项目属性的伴随 GroupBox。这些属性在 TextBoxes 中是可编辑的（绑定到 SelectedItem.[属性]）并且工作正常。 但是其中一个属性是一个列表（定义为 ObservableCollection），我想在 ComboBox 中显示它，所以我将 ItemsSource 绑定到 TreeView 的 SelectedItem.Modes:

<ComboBox Name="FixtureModesListBox" ItemsSource="{Binding ElementName=FixturesTreeView, Path=SelectedItem.Modes}" ItemTemplate="{StaticResource FixtureModeTemplate}" />

这显然不起作用，我得到的错误是：

 BindingExpression path error: 'Modes' property not found on 'object' ''efcFixtureModel' ...

属性确实存在，被设置，是public等

我目前的解决方案 我可以通过使用一些代码隐藏（并引用完全相同的 "path"）来让它工作：

    private void FixturesTreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        if (FixturesTreeView.SelectedItem is efcFixtureModel) // The 1st level/parent items is of a different type
        {
            FixtureModesListBox.ItemsSource = (FixturesTreeView.SelectedItem as efcFixtureModel).Modes;
        }
    }

我想不通为什么这不起作用，而且我在网上找不到任何好的信息。

编辑以包含更多信息：

<TreeView Name="FixturesTreeView" ItemTemplate="{StaticResource FixtureItemTemplate}" SelectedItemChanged="FixturesTreeView_SelectedItemChanged">
</TreeView>

...
        // Assignment of ItemsSource
        FixturesTreeView.ItemsSource = mainWin.Companies;
...

public partial class efcMainWindow : Window
{
    // Definition of Companies
    public ObservableCollection<efcCompany> Companies;

...

// Definition of efcCompany    
public class efcCompany
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Url { get; set; }
    public string Logo { get; set; }
    public int FixtureCount { get { return Fixtures.Count; } }
    public ObservableCollection<efcFixtureModel> Fixtures { get; set; }

    public efcCompany(string name = "", int id = -1, string url = "", string logo = "")
    {
        this.Name = name;
        this.Id = id;
        this.Url = url;
        this.Logo = logo;

        this.Fixtures = new ObservableCollection<efcFixtureModel>();
    }

    public override string ToString()
    {
        return "#" + Id.ToString() + ": " + Name + " (" + Url + ", " + Logo + ")";
    }
}

// Definition of efcFixtureController
public class efcFixtureModel
{
    public int Id { get; set; }
    public int Manufacturer { get; set; }
    public efcFixtureType Type { get; set; }
    public string Name { get; set; }
    public string Image { get; set; }
    public string Description { get; set; }

    public byte TotalChannelCount { get; set; }

    public ObservableCollection<efcFixtureMode> Modes;

    public efcFixtureModel()
    {
        Modes = new ObservableCollection<efcFixtureMode>();
    }

    public override string ToString()
    {
        return "#" + Id.ToString() + ": " + Name + " (" + Type.ToString() + ", " + Image + ", " + Description + ")";
    }
}

Answer 1

您需要将 efcFixtureModel.Modes 从 Field 转换为 属性:

public ObservableCollection<efcFixtureMode> Modes { get; set; }

请阅读What is Difference between Property and Variable in C#

Answer 2

正如我之前所说，您需要将 FixturesTreeView 中的 SelectedItem 绑定到 ViewModel 中类型为 efcFixtureModel 的 属性。

<TreeView Name="FixturesTreeView" ItemTemplate="{StaticResource FixtureItemTemplate}" SelectedItemChanged="FixturesTreeView_SelectedItemChanged"
SelectedItem="{Binding TreeViewSelectedItem}">
</TreeView>

<ComboBox Name="FixtureModesListBox" ItemsSource="{Binding TreeViewSelectedItem.Modes}" ItemTemplate="{StaticResource FixtureModeTemplate}" />