File Stream C#

//-----------------------------------------------------------------------
// 
//     Copyright 2010 INL sprl.
// 
// Fabrice avaux : Date de création 16/10/2010
//-----------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
internal static class PathUtil
{
    internal static string GetRelativePath(string rootPath, string fullPath)
    {
        rootPath = System.IO.Path.GetFullPath(rootPath).ToLowerInvariant();
        string lowerfullPath = System.IO.Path.GetFullPath(fullPath).ToLowerInvariant();
        if (!lowerfullPath.StartsWith(rootPath))
            return fullPath;
        return fullPath.Substring(rootPath.Length);
    }
}