我最近创建了一个用户控件,该控件通知用户他有多少个通知。由于我希望此用户控件仅在有任何通知时才显示自身,因此我创建了一个DataTrigger,该数据绑定到bool并将可见性设置为在没有通知时折叠。它在一开始就可以正常工作,并且用户控件已折叠,但是在我的程序中,我添加了一个通知并在bool上调用NotifyPropertyChanged,但是由于某些未知原因,用户控件仍然保持隐藏状态。
<UserControl.Style>
<Style TargetType="{x:Type UserControl}">
<Setter Property="Visibility"
Value="Visible">
</Setter>
<Style.Triggers>
<DataTrigger Binding="{Binding HasNotifications}"
Value="False">
<Setter Property="Visibility"
Value="Collapsed">
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</UserControl.Style>
private ObservableCollection<Notification> notifications;
public ObservableCollection<Notification> Notifications
{
get { return notifications; }
}
public bool HasNotifications
{
get
{
return Notifications.Count > 0;
}
}
public void AddNotification(Notification notificationToAdd)
{
notifications.Add(notificationToAdd);
NotifyPropertyChanged(nameof(Notifications));
NotifyPropertyChanged(nameof(HasNotifications));
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void NotifyPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
[我还试图将DataTrigger的值设置为相反的值(当HasNotifications为true时将可见性设置为on,但对我来说也没有用。
我复制了您的代码并在3.5和4.7框架下对其进行了测试,并且可以正常工作。我只能在一种情况下重现您的问题,但我想在这里是因为该部分不在您的代码示例中。
仅当数据上下文类不继承自INotifyPropertyChanged
时,它才起作用。否则,最少的代码示例将按预期工作。
public class MyDataContext : INotifyPropertyChanged // <= doesn't work if this is missing
{
private ObservableCollection<Notification> notifications = new ObservableCollection<Notification>();
public ObservableCollection<Notification> Notifications => notifications;
public bool HasNotifications=> Notifications.Count > 0;
public void AddNotification(Notification notificationToAdd)
{
notifications.Add(notificationToAdd);
NotifyPropertyChanged(nameof(Notifications));
NotifyPropertyChanged(nameof(HasNotifications));
}
private ICommand _AddNotification;
public ICommand AddNotificationCMD => _AddNotification ?? (_AddNotification = new RelayCommand<object>(a => AddNotificationCommand(a)));
private void AddNotificationCommand(object item)
{
AddNotification(new Notification());
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void NotifyPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
<Window x:Class="WpfApp_3_5_framework_test.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApp_3_5_framework_test"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid>
<local:UserControl1/>
<Button Content="Add Notification" Command="{Binding AddNotificationCMD}" Height="20" Width="200" />
</Grid>
</Window>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.DataContext = new MyDataContext();
}
}
<UserControl x:Class="WpfApp_3_5_framework_test.UserControl1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:WpfApp_3_5_framework_test"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<UserControl.Style>
<Style TargetType="{x:Type UserControl}">
<Setter Property="Visibility"
Value="Visible">
</Setter>
<Style.Triggers>
<DataTrigger Binding="{Binding HasNotifications}"
Value="False">
<Setter Property="Visibility"
Value="Collapsed">
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</UserControl.Style>
<Grid>
<StackPanel>
<Border Width="100" Height="100" Background="Red"/>
</StackPanel>
</Grid>
</UserControl>