我的ViewModel中有4个类，它们实现了IPage接口（我创建的接口）。在我的应用程序的ViewModel中，我有一个IPage类型的CurrentPage属性。
在我的应用的视图层中，我有一个ContentControl，其内容绑定到CurrentPage属性。
因此，当我使用以下代码时，WPF将找不到合适的DataTemplate
<UserControl ...>
<ContentControl Content="{Binding CurrentPage, Mode=OneWay}"
VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<ContentControl.Resources>
<DataTemplate DataType="{x:Type operation:OperationListPageVM}">
<pages1:OperationListPageV/>
</DataTemplate>
<DataTemplate DataType="{x:Type operation:OperationDetailPageVM}">
<pages1:OperationDetailPageV/>
</DataTemplate>
<DataTemplate DataType="{x:Type part:PartListPageVM}">
<pages1:PartListPageV/>
</DataTemplate>
<DataTemplate DataType="{x:Type part:PartDetailPageVM}">
<pages1:PartDetailPageV/>
</DataTemplate>
<DataTemplate DataType="{x:Type pages:SettingsPageVM}">
<pages1:SettingsPageV/>
</DataTemplate>
</ContentControl.Resources>
</ContentControl>
</UserControl>
但是，如果我只将一个DataTemplate作为ContentControl.ContentTemplate，那么它将正确应用它
<UserControl ...>
<ContentControl Content="{Binding CurrentPage, Mode=OneWay}"
VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<ContentControl.ContentTemplate>
<DataTemplate DataType="{x:Type operation:OperationListPageVM}">
<pages1:OperationListPageV/>
</DataTemplate>
</ContentControl.ContentTemplate>
</ContentControl>
</UserControl>
如果我然后将这些DataTemplates作为资源放回去，给它们一个键并创建一个DataTemplateSelector并添加
ContentTemplateSelector="{StaticResource PageTemplateSelector}"
使用DataTemplateSelector的ControlTemplate：
using System.Windows;
using System.Windows.Controls;
using MaintenanceModuleV3.ViewModel;
using MaintenanceModuleV3.ViewModel.Pages;
using MaintenanceModuleV3.ViewModel.Pages.Operation;
using MaintenanceModuleV3.ViewModel.Pages.Part;
namespace MaintenanceModuleV3.View.TemplateSelector {
public class PageTemplateSelector : DataTemplateSelector {
public override DataTemplate SelectTemplate(object item, DependencyObject container) {
if (AppVM.Instance.CurrentPage != null) {
if (AppVM.Instance.CurrentPage is OperationListPageVM) {
return (container as FrameworkElement).FindResource("OperationListPageTemplate") as DataTemplate;
} else if (AppVM.Instance.CurrentPage is OperationDetailPageVM) {
return (container as FrameworkElement).FindResource("OperationDetailPageTemplate") as DataTemplate;
} else if (AppVM.Instance.CurrentPage is PartListPageVM) {
return (container as FrameworkElement).FindResource("PartListPageTemplate") as DataTemplate;
} else if (AppVM.Instance.CurrentPage is PartDetailPageVM) {
return (container as FrameworkElement).FindResource("PartDetailPageTemplate") as DataTemplate;
} else if (AppVM.Instance.CurrentPage is SettingsPageVM) {
return (container as FrameworkElement).FindResource("SettingsPageTemplate") as DataTemplate;
}
}
return null;
}
}
}
然后选择正确的DataTemplate。
如果在这种情况下将DataTemplate放在元素资源中，为什么WPF不会选择正确的DataTemplate？
谢谢
注意：使用Framework 3.5
编辑：我注意到第二个问题：DataTemplates中的DataContext为null。这是为什么？为什么他们不将CurrentPage作为DataContext？当我直接设置ContentTemplate时就是这种情况。 WPF似乎不喜欢绑定到接口类型的属性。
编辑2：如果我在其构造函数中显式设置OperationListPageV的DataContext并使用TemplateSelector一切正常，但为什么我必须使用它们？
编辑3：完整的ViewModel代码，如果它有帮助：
应用ViewModel
public class AppVM : INotifyPropertyChanged {
#region constructor
private AppVM() {
AppM.LanguageChanged += (sender, args) => {
onPropertyChanged("CurrentLanguage");
};
AppM.NbDaysAvgChanged += (sender, args) => {
onPropertyChanged("NbDaysAvg");
};
AppM.NbDaysMenuNotificationChanged += (sender, args) => {
onPropertyChanged("NbDaysMenuNotification");
};
}
#endregion
#region business
#endregion
#region events
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void onPropertyChanged(string propertyName) {
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
#region properties
private static AppVM _instance;
public static AppVM Instance {
get { return _instance ?? (_instance = new AppVM()); }
}
#region notifypropertychanged
private OperationListPageVM _currentPage = OperationListPageVM.Instance;
public OperationListPageVM CurrentPage {
get { return _currentPage; }
set {
_currentPage = value;
onPropertyChanged("CurrentPage");
}
}
public Language CurrentLanguage {
get { return AppM.CurrentLanguage; }
}
public int NbDaysMenuNotification {
get { return AppM.NbDaysMenuNotification; }
}
public int NbDaysAvg {
get { return AppM.NbDaysAvg; }
}
public Dictionary<String, String> AvailableTranslations {
get { return AppM.AvailableTranslations; }
}
#endregion
#region commands
#endregion
#endregion
}
我要显示ViewModel的页面
public sealed class OperationListPageVM : INotifyPropertyChanged, IPage {
#region constructor
private OperationListPageVM() {
//fill the available operations with data stored in the App Model coming from the DataBase
foreach (MaintenanceOperation operation in AppM.Operations) {
AvailableOperations.Add(new MaintenanceOperationVM(operation));
}
foreach (MaintenanceOperationVM operation in AvailableOperations) {
DisplayedOperations.Add(operation);
}
}
#endregion
#region business
#endregion
#region events
public event PropertyChangedEventHandler PropertyChanged;
private void onPropertyChanged(string propertyName) {
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
#region properties
private static OperationListPageVM _instance;
public static OperationListPageVM Instance {
get { return _instance ?? (_instance = new OperationListPageVM()); }
}
#region notifypropertychanged
private ObservableCollection<MaintenanceOperationVM> _displayedOperations = new ObservableCollection<MaintenanceOperationVM>();
public ObservableCollection<MaintenanceOperationVM> DisplayedOperations {
get { return _displayedOperations; }
set {
_displayedOperations = value;
onPropertyChanged("DisplayedOperations");
}
}
private readonly List<MaintenanceOperationVM> _availableOperations = new List<MaintenanceOperationVM>();
internal List<MaintenanceOperationVM> AvailableOperations {
get { return _availableOperations; }
}
#endregion
#region commands
#endregion
#endregion
}
我要显示的页面的View层（OperationListPageV）
<UserControl x:Class="MaintenanceModuleV3.View.Pages.OperationListPageV"
...>
<touch:ScrollFriction2>
<ListBox ItemsSource="{Binding DisplayedOperations}">
<ListBox.ItemContainerStyle>
<Style TargetType="{x:Type ListBoxItem}">
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
</Style>
</ListBox.ItemContainerStyle>
<ListBox.ItemTemplate>
<DataTemplate DataType="{x:Type viewModel:MaintenanceOperationVM}">
<view:MaintenanceOperationV/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</touch:ScrollFriction2>
</UserControl>
如果您需要更多代码，请提出要求。谢谢！
答案 0 :(得分：0)
将模板放在ItemControl的Resources中。我不知道为什么他们这样做，但他们应该比ContentControl高出一层