我有ViewModel （实现INotifyPropertyChanged ）的背景和阶级Category它只有一个类型的属性string 。 我的组合框的SelectedItem被绑定到一个类的实例。 当我改变实例的值，的SelectedItem不被更新和ComboBox没有改变。
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}"/>
属性：
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;
}
什么我想的是：当我设置
NodeCategory = some_list_of_other_objects.Category;
有在选择的项目Combobox与适当DisplayMemberPath
你在这一行设定的类别 -
NodeCategory = some_list_of_other_objects.Category;
并在分类收集（中所存在ItemsSource="{Binding Categories}" ）应该是指同一个对象。 如果他们不那么SelectedItem将无法正常工作。
解决方案1 -
您也可以尝试使用SelectedValuePath这样的-
<ComboBox x:Name="categoryComboBox"
ItemsSource="{Binding Categories}"
DisplayMemberPath="Name"
SelectedValuePath="Name"
SelectedValue="{Binding NodeCategory, Mode=TwoWay}" />
和代码，你可以做这样的事情 -
private string _NodeCategory;
public string NodeCategory
{
get
{
return _NodeCategory;
}
set
{
_NodeCategory = value;
OnPropertyChanged("NodeCategory");
}
}
并设置选择的项目是这样 -
NodeCategory = some_list_of_other_objects.Category.Name;
并使用所选值这样的 -
Category selectedCategory =
some_list_of_other_objects.FirstOrDefault(cat=> cat.Name == NodeCategory);
要么
Category selectedCategory =
Categories.FirstOrDefault(cat=> cat.Name == NodeCategory);
解决方案2 -
另一种可能的解决方案可能是 -
NodeCategory =
Categories.FirstOrDefault(cat=> cat.Name == some_list_of_other_objects.Category.Name);
这样您NodeCategory属性将有一个对象的参考Categories收集和SelectedItem会工作。
你的XAML需要一对夫妇的修改，但我认为真正的问题是你已经发布的代码，我不认为说的是完整的故事。 对于初学者来说，你的组合框ItemSource势必属性称为类别，但你不显示你如何将此属性编码或如何NodeCategory属性最初同步与该项目。
请尝试使用下面的代码，你会看到，当用户更改ComboBox中值显示所选的项目保持同步。
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;
}
从我的小例子：
注：这是设置只是一个字符串（或从另一个列表中一个类别），但基本应该是同样在这里：
基本上做到这一点：
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>
并在窗口的视图模型
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;
}
}
有了这个小类的帮助：
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();
}
}
而这个项目的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");
}
}
}
如果组合框绑定对象类视图模型，而SelectionBoxItem发送对象（在SelectionChanged在后面的代码）已经不是那种类型，这意味着它仍然加载。
ComboBox combo = sender as ComboBox;
if (combo.SelectionBoxItem.GetType() == typeof(BindedClass))
{
// Not loading
}
