ComboBox IsEnabled 绑定问题在 Silverlight Xaml

Question

I have a ComboBox whose xaml is as follows

<ComboBox Name="ComboBoxDiscussionType" IsEnabled="{Binding ElementName=ComboBoxDiscussionType, Path=Items.Count, Converter={StaticResource ComboBoxItemsCountToBoolConverter}}"/>

and the converter takes the Items.Count and checks if its greater than 0 if its greater than 0 then enable it else disable it

The goal is enable the ComboBox if the ComboBox only if it has Items in it else disable it, ( self Binding to its item.count )

the following is my converter,

public class ComboBoxItemsCountToBoolConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return (int)value > 0;
    }
    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return null;
    }
}

how do i achieve it? right now the above Binding gives me an error

Answer 1

For reasons that I don't understand, on Silverlight the value as seen by the converter is of type double but it should be int . In fact it is an int on WPF.

But since this is the case, just processing it as a double fixed the problem:

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    return (int)(double)value > 0;
}

Strangely enough, a more traditional relative source binding doesn't work either:

<Binding RelativeSource="{RelativeSource Self}" .../>

but your original element name binding does:

<ComboBox Name="ComboBoxDiscussionType" IsEnabled="{Binding ElementName=ComboBoxDiscussionType, Path=Items.Count, Converter={StaticResource ComboBoxItemsCountToBoolConverter}}"/>

This seems pretty buggy to me, but Silverlight is a strange beast sometimes.