Xaml's most popular converter.

VisibilityConverter.cs

using System;
using System.Windows;
using System.Windows.Data;
using System.ComponentModel;

namespace MonkeyBusters
{
    public class VisibilityConverter : IValueConverter
    {
        public Boolean TrueIsVisible { get; set; }

        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (DesignerProperties.IsInDesignTool) return Visibility.Visible;

            bool b;

            if (value is int)
            {
                b = (int)value > 0;
            }
            else if (value is bool)
            {
                b = (bool)value;
            }
            else if (value == null)
            {
                return GetVisbility(false);
            }
            else if (value.GetType().IsClass)
            {
                return GetVisbility(true);
            }
            else
            {
                throw new NotImplementedException(String.Format("Type {0} is not valid for this conversion.", value.GetType().Name));
            }

            return GetVisbility(b);
        }

        Visibility GetVisbility(Boolean b)
        {
            return (b == TrueIsVisible) ? Visibility.Visible : Visibility.Collapsed;
        }

        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}