18

我在背景和类中ViewModel（已实现）只有一个类型的属性。我的 ComboBox SelectedItem 绑定到类别的实例。当我更改实例的值时，未更新 SelectedItem 并且未更改 Combobox。INotifyPropertyChangedCategorystring

编辑：代码

组合框：

<ComboBox x:Name="categoryComboBox" Grid.Column="1"  Grid.Row="3" Grid.ColumnSpan="2" 
          Margin="10" ItemsSource="{Binding Categories}"
          DisplayMemberPath="Name" SelectedValue="{Binding NodeCategory, Mode=TwoWay}"/>

财产：

private Category _NodeCategory;
public Category NodeCategory
{
    get
    {
        return _NodeCategory;
    }
    set
    {
        _NodeCategory = value;
        OnPropertyChanged("NodeCategory");
    }
}

[Serializable]
public class Category : INotifyPropertyChanged
{
    private string _Name;
    [XmlAttribute("Name")]
    public string Name
    {
        get
        {
            return _Name;
        }
        set
        {
            _Name = value;
            OnPropertyChanged("Name");
        }
    }

    public void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    [field:NonSerialized]
    public event PropertyChangedEventHandler PropertyChanged;
}

我正在尝试的是：当我设置

NodeCategory = some_list_of_other_objects.Category;

Combobox以适当的方式选择该项目DisplayMemberPath

4

4 回答 4

25

您在此行中设置的类别 -

NodeCategory = some_list_of_other_objects.Category;

并且您的 Categories 集合（ItemsSource="{Binding Categories}"）中的一个应该指的是同一个对象。如果他们不是，那么SelectedItem将无法正常工作。

解决方案 1 -

你也可以尝试这样使用SelectedValuePath——

<ComboBox x:Name="categoryComboBox" 
          ItemsSource="{Binding Categories}"
          DisplayMemberPath="Name" 
          SelectedValuePath="Name" 
          SelectedValue="{Binding NodeCategory, Mode=TwoWay}" />

在代码中你可以做这样的事情 -

private string _NodeCategory;
public string NodeCategory
{
    get
    {
        return _NodeCategory;
    }
    set
    {
        _NodeCategory = value;
        OnPropertyChanged("NodeCategory");
    }
}

并像这样设置选定的项目 -

NodeCategory = some_list_of_other_objects.Category.Name;

并使用这样的选定值 -

Category selectedCategory = 
   some_list_of_other_objects.FirstOrDefault(cat=> cat.Name == NodeCategory);

或者

Category selectedCategory = 
   Categories.FirstOrDefault(cat=> cat.Name == NodeCategory);

解决方案 2 -

另一种可能的解决方案是 -

NodeCategory = 
  Categories.FirstOrDefault(cat=> cat.Name == some_list_of_other_objects.Category.Name);

这样，您的NodeCategory属性将具有Categories集合中对象的引用并且SelectedItem可以工作。

于 2012-06-16T10:28:42.543 回答
5

您的 XAML 需要进行一些修改，但我认为真正的问题在于您发布的代码，我认为这并不能说明全部情况。对于初学者，您的组合框ItemSource绑定到一个名为 Categories 的属性，但您没有显示该属性是如何编码的，或者您的NodeCategory属性最初是如何与项目同步的。

尝试使用以下代码，您将看到所选项目在用户更改组合框中的值时保持同步。

XAML

<Window x:Class="WpfApplication1.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">
<StackPanel>
    <ComboBox x:Name="categoryComboBox"
              Grid.Column="1"
              Grid.Row="3"
              Grid.ColumnSpan="2"
              Margin="10"
              ItemsSource="{Binding Categories}"
              DisplayMemberPath="Name"
              SelectedItem="{Binding NodeCategory}" />
    <Label Content="{Binding NodeCategory.Name}" />
</StackPanel>

代码隐藏

public partial class MainWindow : Window, INotifyPropertyChanged
{
    private ObservableCollection<Category> _categories = new ObservableCollection<Category>
    {
        new Category { Name = "Squares"},
        new Category { Name = "Triangles"},
        new Category { Name = "Circles"},
    };

    public MainWindow()
    {
        InitializeComponent();
        NodeCategory = _categories.First();
        this.DataContext = this;
    }

    public IEnumerable<Category> Categories
    {
        get { return _categories; }
    }

    private Category _NodeCategory;
    public Category NodeCategory
    {
        get
        {
            return _NodeCategory;
        }
        set
        {
            _NodeCategory = value;
            OnPropertyChanged("NodeCategory");
        }
    }

    public void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

[Serializable]
public class Category : INotifyPropertyChanged
{
    private string _Name;
    [XmlAttribute("Name")]
    public string Name
    {
        get
        {
            return _Name;
        }
        set
        {
            _Name = value;
            OnPropertyChanged("Name");
        }
    }

    public void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    [field: NonSerialized]
    public event PropertyChangedEventHandler PropertyChanged;
}
于 2012-06-16T10:12:08.093 回答
2

从我的小例子：

注意：这只是设置一个字符串（或另一个列表中的一个类别），但这里的基础应该是相同的：

基本上这是完成的：

private void button1_Click(object sender, RoutedEventArgs e)
{
    (this.DataContext as ComboBoxSampleViewModel).SelectCategory("Categorie 4");
}

这是我的 XAML：

<Grid>
    <ComboBox Height="23" HorizontalAlignment="Left" Margin="76,59,0,0"   
              Name="comboBox1" VerticalAlignment="Top" Width="120" 
              ItemsSource="{Binding List.Categories}" 
              DisplayMemberPath="Name" 
              SelectedValue="{Binding NodeCategory, Mode=TwoWay}" />
    <Button Content="Button" Height="27" HorizontalAlignment="Left" 
            Margin="76,110,0,0" Name="button1" VerticalAlignment="Top" 
            Width="120" Click="button1_Click" />
</Grid>

并在 Window 的 ViewModel 中

class ComboBoxSampleViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged(string info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    public CategoryList List { get; set; }

    public ComboBoxSampleViewModel()
    {
        this.List = new CategoryList();
        NodeCategory = List.Selected;
    }

    private ComboBoxSampleItemViewModel nodeCategory;
    public ComboBoxSampleItemViewModel NodeCategory
    {
        get
        {
            return nodeCategory;
        }
        set
        {
            nodeCategory = value;
            NotifyPropertyChanged("NodeCategory");
        }
    }

    internal void SelectCategory(string p)
    {
        this.List.SelectByName(p);
        this.NodeCategory = this.List.Selected;
    }
}

在这个小班的帮助下：

public class CategoryList
{
    public ObservableCollection<ComboBoxSampleItemViewModel> Categories { get; set; }
    public ComboBoxSampleItemViewModel Selected { get; set; }
    public CategoryList()
    {
        Categories = new ObservableCollection<ComboBoxSampleItemViewModel>();

        var cat1 = new ComboBoxSampleItemViewModel() { Name = "Categorie 1" };
        var cat2 = new ComboBoxSampleItemViewModel() { Name = "Categorie 2" };
        var cat3 = new ComboBoxSampleItemViewModel() { Name = "Categorie 3" };
        var cat4 = new ComboBoxSampleItemViewModel() { Name = "Categorie 4" };

        Categories.Add(cat1);
        Categories.Add(cat2);
        Categories.Add(cat3);
        Categories.Add(cat4);

        this.Selected = cat3;
    }

    internal void SelectByName(string p)
    {
        this.Selected = this.Categories.Where(s => s.Name.Equals(p)).FirstOrDefault();
    }
}

而这个 Item ViewModel

public class ComboBoxSampleItemViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged(string info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    private string name;

    public string Name 
    { 
        get
        {
            return name;
        }
        set
        {
            name = value;
            NotifyPropertyChanged("Name");
        }
    }
}
于 2012-06-16T10:43:38.920 回答
0

如果 Combobox 绑定到 View Model 的对象类，而SelectionBoxItem发送者对象（在SelectionChanged后面的代码中）没有该类型，则表示它仍在加载。

ComboBox combo = sender as ComboBox;
if (combo.SelectionBoxItem.GetType() == typeof(BindedClass))
{
            // Not loading
}
于 2019-04-18T17:33:11.900 回答