WPF Combobox SelectedIndex屬性綁定不工作

Question

我想將ComboBox的SelectedIndex屬性綁定到我的ViewModel。這是代碼。

的XAML：

<ComboBox x:Name="BloodGroupFilter" SelectedIndex="{Binding Path=SelectedBloodGroupIndex, Mode=TwoWay}"> 
    <ComboBox.ItemsSource> 
     <CompositeCollection> 
      <ComboBoxItem Foreground="red" FontStyle="Italic">No Filter</ComboBoxItem> 
      <CollectionContainer Collection="{Binding Source={StaticResource BloodGroupEnum}}"/> 
     </CompositeCollection> 
    </ComboBox.ItemsSource> 
</ComboBox> 

視圖模型

private int _selectedBloodGroupIndex = 4; 
public int SelectedBloodGroupIndex { 
    get { return _selectedBloodGroupIndex; } 
    set { 
     _selectedBloodGroupIndex = value; 
    } 
} 

正如你可以看到我想設置組合框的爲 「4」 的SelectedIndex的。這不會發生，並且SelectedIndex被設置爲0.另外，當用戶選擇組合框的特定項目時，我期望ViewModel的SelectedBloodGroupIndex屬性將自己更新爲當前選擇的組合框項目，但是這也不會發生。 ViewModel屬性永遠不會被調用（set和get）。上述代碼的綁定失敗的任何原因。

更新

<UserControl.Resources> 
    <ObjectDataProvider x:Key="BloodGroupEnum" MethodName="GetValues" ObjectType="{x:Type sys:Enum}"> 
     <ObjectDataProvider.MethodParameters> 
      <x:Type TypeName="enums:BloodGroup" /> 
     </ObjectDataProvider.MethodParameters> 
    </ObjectDataProvider> 
</UserControl.Resources> 

Answer 1

你需要通知物業在您的視圖模型的SelectedBloodGroupIndex的二傳手改變。我希望你確實有PropertyChanged事件的想法。

<Window x:Class="WpfApplication4.MainWindow" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:myWindow="clr-namespace:WpfApplication4" 
    Title="MainWindow" Height="800" Width="800" WindowStartupLocation="CenterScreen"> 

<Grid> 
    <ComboBox SelectedIndex="{Binding SelectedIndex}"> 
     <ComboBoxItem Content="1"/> 
     <ComboBoxItem Content="2"/> 
     <ComboBoxItem Content="3"/> 
     <ComboBoxItem Content="4"/> 
     <ComboBoxItem Content="5"/> 
    </ComboBox> 
</Grid> 

public partial class MainWindow :Window 
{ 
    public MainWindow() 
    { 
     InitializeComponent(); 
     DataContext = new MyViewModel(); 
    } 
} 

public class MyViewModel :INotifyPropertyChanged 
{ 
    public MyViewModel() 
    { 
     SelectedIndex = 2; 
    } 
    private int _selectedIndex; 
    public int SelectedIndex 
    { 
     get 
     { 
      return _selectedIndex; 
     } 
     set 
     { 
      _selectedIndex = value; 
      Notify("SelectedIndex"); 
     } 
    } 

    public event PropertyChangedEventHandler PropertyChanged; 

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