MVVM Prism 5 WPF 和组合框

Question

我不明白为什么当我在另一个组合框中进行选择时我的组合框没有更新。我还是 MVVM 的新手，但理论上我的代码应该可以工作。我可以在加载表单时填充组合，但我需要用新值刷新组合，但这是行不通的。我可以看到它正在检索新值，但它从未在表单上显示它们。

我的 XAML 看起来像这样：

<ComboBox Grid.Column="1" ItemsSource="{Binding Path=Vendors}" SelectedItem="{Binding SelectedVendor, Mode=TwoWay}"   HorizontalAlignment="Left" Margin="24,12,0,11" Grid.Row="3" VerticalAlignment="Center" Width="293" />
<ComboBox x:Name="VendorProductServiceCB" HorizontalAlignment="Left" Margin="20.6,16.2,0,55.4" VerticalAlignment="Center" Width="293" Grid.Row="7" Grid.Column="1" ItemsSource="{Binding Path=VendorProductServices, UpdateSourceTrigger=PropertyChanged}" DisplayMemberPath="Name" SelectedItem="{Binding Path=SelectedVendorProductService, Mode=TwoWay}" Height="22"/>

我的 ViewModel 代码是这样的：

public ObservableCollection<string> Vendors { get; set; } 
public ObservableCollection<VendorProductService> VendorProductServices { get; private set; }

public VendorProductService SelectedVendorProductService
    {
        get { return _selectedVendorProductService; }
        set { SetProperty(ref _selectedVendorProductService, value); }
    }

public string SelectedVendor
    {
        get { return _selectedVendor; }
        set
        {
            SetProperty(ref _selectedVendor, value);            
            SelectionChangedCommand.Execute(this);

        }               
    }

public FormSelectionViewModel()
    {
        Vendors = new ObservableCollection<string>(FetchVendors());

        VendorProductServices = new ObservableCollection<VendorProductService>(FetchVendorProductServices(_selectedVendor));  

        SelectionChangedCommand = new DelegateCommand(SelectionChanged);
    }
public  void SelectionChanged()
    {

        VendorProductServices = new ObservableCollection<VendorProductService>(FetchVendorProductServices(_selectedVendor)); 

    }

Answer 1

您没有引发 VendorProductServices 的 PropertyChanged 事件，因为它是自动属性。

要么将其更改为：

private ObservableCollection<VendorProductService> _vendorProductServices;
public ObservableCollection<VendorProductService> VendorProductServices 
{ 
    get { return _vendorProductServices; }
    private set { SetProperty(ref _vendorProductServices, value); }
}

或者将您的集合属性更改为只读并使用 .Clear() 和 .Add() 而不是创建新集合。

MVVM Prism 5 WPF 和组合框

MVVM Prism 5 WPF and combo boxes

c#

wpf

prism

mvvm