我拥有的是一个具有IsReadOnly属性的对象。如果此属性为true，我想将按钮上的IsEnabled属性设置为false(例如)。
我愿意相信我可以像IsEnabled="{绑定路径=!IsReadOnly}”，但这与WPF不兼容。
我是否不得不经历所有的样式设置?对于将一个bool值设置为另一个bool值的倒数这样简单的事情来说，似乎太啰嗦了。
<Button.Style>
<Style TargetType="{x:Type Button}">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=IsReadOnly}" Value="True">
<Setter Property="IsEnabled" Value="False" />
</DataTrigger>
<DataTrigger Binding="{Binding Path=IsReadOnly}" Value="False">
<Setter Property="IsEnabled" Value="True" />
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
这个方法也适用于可为空的bool。
[ValueConversion(typeof(bool?), typeof(bool))]
public class InverseBooleanConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (targetType != typeof(bool?))
{
throw new InvalidOperationException("The target must be a nullable boolean");
}
bool? b = (bool?)value;
return b.HasValue && !b.Value;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return !(value as bool?);
}
#endregion
}
不知道这是否与XAML相关，但在我简单的Windows应用程序中，我手动创建了绑定，并添加了一个格式事件处理程序。
public FormMain() {
InitializeComponent();
Binding argBinding = new Binding("Enabled", uxCheckBoxArgsNull, "Checked", false, DataSourceUpdateMode.OnPropertyChanged);
argBinding.Format += new ConvertEventHandler(Binding_Format_BooleanInverse);
uxTextBoxArgs.DataBindings.Add(argBinding);
}
void Binding_Format_BooleanInverse(object sender, ConvertEventArgs e) {
bool boolValue = (bool)e.Value;
e.Value = !boolValue;
}
I did something very similar. I created my property behind the scenes that enabled the selection of a combobox ONLY if it had finished searching for data. When my window first appears, it launches an async loaded command but I do not want the user to click on the combobox while it is still loading data (would be empty, then would be populated). So by default the property is false so I return the inverse in the getter. Then when I'm searching I set the property to true and back to false when complete.
private bool _isSearching;
public bool IsSearching
{
get { return !_isSearching; }
set
{
if(_isSearching != value)
{
_isSearching = value;
OnPropertyChanged("IsSearching");
}
}
}
public CityViewModel()
{
LoadedCommand = new DelegateCommandAsync(LoadCity, LoadCanExecute);
}
private async Task LoadCity(object pArg)
{
IsSearching = true;
//**Do your searching task here**
IsSearching = false;
}
private bool LoadCanExecute(object pArg)
{
return IsSearching;
}
然后，对于组合框，我可以直接绑定到IsSearching:
<ComboBox ItemsSource="{Binding Cities}" IsEnabled="{Binding IsSearching}" DisplayMemberPath="City" />
这个方法也适用于可为空的bool。
[ValueConversion(typeof(bool?), typeof(bool))]
public class InverseBooleanConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (targetType != typeof(bool?))
{
throw new InvalidOperationException("The target must be a nullable boolean");
}
bool? b = (bool?)value;
return b.HasValue && !b.Value;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return !(value as bool?);
}
#endregion
}
我遇到了一个倒置的问题，但是有一个简洁的解决方法。
动机是XAML设计器会显示一个空控件，例如当没有数据上下文/没有MyValues (itemssource)时。
初始代码:当MyValues为空时隐藏控件。
改进的代码:当MyValues为非空或空时显示控制。
当然，问题是如何表达“1个或多个项目”，这与0个项目相反。
<ListBox ItemsSource={Binding MyValues}">
<ListBox.Style x:Uid="F404D7B2-B7D3-11E7-A5A7-97680265A416">
<Style TargetType="{x:Type ListBox}">
<Style.Triggers>
<DataTrigger Binding="{Binding MyValues.Count}">
<Setter Property="Visibility" Value="Collapsed"/>
</DataTrigger>
</Style.Triggers>
</Style>
</ListBox.Style>
</ListBox>
我通过添加:
<DataTrigger Binding="{Binding MyValues.Count, FallbackValue=0, TargetNullValue=0}">
因此，为绑定设置默认值。当然，这并不适用于所有类型的逆问题，但帮助我用干净的代码。
