// Copyright (c) 2017 schick Informatik
// Description: Helper converter for empty image source
//

using System;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
using System.Windows.Markup;

namespace ENI2.Util
{
    public class NullImageConverter : MarkupExtension, IValueConverter
    {

        #region MarkupExtension implementation

        private static NullImageConverter _converter = null;
        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            if (_converter == null)
            {
                _converter = new NullImageConverter();
            }
            return _converter;
        }

        #endregion

        #region IValueConverter implementation

        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (value == null)
                return DependencyProperty.UnsetValue;
            return value;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            // According to https://msdn.microsoft.com/en-us/library/system.windows.data.ivalueconverter.convertback(v=vs.110).aspx#Anchor_1
            // (kudos Scott Chamberlain), if you do not support a conversion 
            // back you should return a Binding.DoNothing or a 
            // DependencyProperty.UnsetValue
            return Binding.DoNothing;
            // Original code:
            // throw new NotImplementedException();
        }

        #endregion

    }
}