using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Data;

namespace xxxxxx
{
    public class IndexConverter : IValueConverter
    {
        #region IValueConverter Members

        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            int intValue;
            if (value != null)
            {
                bool isInt = int.TryParse(value.ToString(), out intValue);
                if (isInt)
                {
                    if (intValue == -1)
                    {
                        return null;
                    }
                }
            }
            return (int)value + 1;
        }

        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return null;
        }

        #endregion
    }
}
____________________________________________________________________
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Data;

namespace xxxxxx
{
    public class ValueConverter : IValueConverter
    {
        #region IValueConverter Members

        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return value;
        }

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

        #endregion
    }
}