WPF multi-binding with LINQ: BooleanToVisibilityMultiValueConverter

BooleanToVisibilityMultiValueConverter.cs

using System;
using System.Globalization;
using System.Linq;
using System.Windows;
using System.Windows.Data;

namespace LexusDashboard.ValueConverters
{
    public sealed class BooleanToVisibilityMultiValueConverter : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            var flag = false;
            if (values == null) return Visibility.Collapsed;

            if (values.All(i => i is bool))
            {
                flag = values.OfType<bool>()
                    .Aggregate((x, y) => x && y);
            }
            else if (values.All(i => i is bool?))
            {
                flag = values.OfType<bool?>()
                    .Select(i => i.GetValueOrDefault())
                    .Aggregate((x, y) => x && y);
            }
            if (parameter != null)
            {
                if (bool.Parse((string)parameter))
                {
                    flag = !flag;
                }
            }
            if (flag)
            {
                return Visibility.Visible;
            }
            else
            {
                return Visibility.Collapsed;
            }
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            var back = ((value is Visibility) && (((Visibility)value) == Visibility.Visible));
            if (parameter != null)
            {
                if ((bool)parameter)
                {
                    back = !back;
                }
            }

            return new[] { (object)back };
        }
    }
}