WPF设计时解析不同

Question

I'm having an issue where my MarkupExtension is behaving differently at designtime, or rather the xaml parser is providing different values.

my class:

class FormattableConverter : MarkupExtension, IValueConverter
{
    public FormattableConverter(string format)
    {
        Format = format;
    }

    public string Format { get; set; }

    public override void ProvideValue(IServiceProvider serviceProvider)
    {
        return this;
    }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var formattable = value as IFormattable;
        return formattable?.ToString(Format, culture);
    }

    /* ConvertBack returns NotImplementedException */
}

I'm using it to show a DateTime value.:

<HeaderedContentControl Content="{Binding DateTimeValue, Converter={c:FormattableConverter 'hh\\:mm\\:ss'}}"
                        /* Other parameters */ />

When breaking during runtime, IntelliSense shows the format is hh\\\\:mm\\\\:ss , and formatting works.

But in the designer a FormatException is thrown: Input string was not in a correct format.

If i debug the designer (Attaching to XDesProc.exe) IntelliSence show me that the format is hh:mm:ss ; The backslashes are gone.

I've tried:

• 'hh\\\\:mm\\\\:ss'
• 'hh\\:mm\\:ss'
• {}hh\\\\:mm\\\\:ss
• Format='hh\\\\\\\\:mm\\\\\\\\:ss' (this works in designer, but not runtime)
• Format=hh\\\\\\\\:mm\\\\\\\\:ss (this works in designer, but not runtime)
• Format=hh\\\\:mm\\\\:ss
• other combinations of above

Any idea why the parser provides different string values?

Answer 1

Try this:

On the top of your UserControl/Window:

<Window.Resources>
    <c:FormattableConverter x:Key="formattableConverter" />
    <sys:String x:Key="myParameter"> hh\\:mm\\:ss </sys:String>
</Window.Resources>

and then in the control:

<HeaderedContentControl Content="{Binding DateTimeVale, 
                                          Converter={StaticResource formattableConverter} 
                                          ConverterParameter={StaticResource myParameter}}">

</HeaderedContentControl>

Still if you have any problems, then please post a sample project.