WPF MVVM依赖项属性获取负值

Question

I have two buttons, SEND and UNSEND. I want to enable or disable the buttons using the boolean IsSended .

I've created a dependency property which can be used to enable one of the buttons, but how I can take the negative value to control the other button?

VIEW

dxb:BarButtonItem Content="SEND" IsEnabled="{Binding !IsSent}" 
dxb:BarButtonItem Content="UNSEND" IsEnabled="{Binding IsSent}" 

VIEWMODEL

public Boolean IsSent
{
   get { return (Boolean) GetValue(IsSendedProperty); }
   set { SetValue(IsSendedProperty, value); }
}

public static readonly DependencyProperty IsSendedProperty = DependencyProperty.Register("IsSent", typeof(Boolean), typeof(ViewModel), new PropertyMetadata(default(Boolean)));

Answer 1

There are a number of was to do this in WPF; IValueConverters , DataTemplate or overriding the ControlTemplate .

It is hard to know which would be the best in the long run for your particular application, but the simplest to show here is the IValueConverter .

Add a class called, for example, NegateBoolConverter

public class NegateBoolConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return !(bool)value;
    }


    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return !(bool)value;
    }
}

Create an instance of this class in XAML (I put all my converters all the way up in the App.xaml , but you could put it in the <Window.Resources> section.

  <Window.Resources>
    <local:NegateBoolConverter x:Key="MyConverter"/>
  </Window.Resources>

where local: is a namespace to the converter class

Then your binding becomes:

  <dxb:BarButtonItem Content="SEND" IsEnabled="{Binding IsSended, Converter={StaticResource MyConverter}}">