根据一个绝对路径获取相对路径的方法

static void Main(string[] args)
{
    string a = @"c:\a\b\c\d";
    string b = @"c:\a\b\e\f\1.txt";
    int n = 0;
    Console.WriteLine(GetRelativePaths(b, a));
    Console.ReadKey();
}

public static string GetRelativePaths(string path, string current)
{
    string a = current.ToLower();
    string b = path.ToLower();
    int i = 0;
    for (; i < Math.Min(a.Length,b.Length); i++)
    {
        if (a[i] != b[i]) break;
    }
    string cur = Regex.Replace(a.Substring(i - 1), @"\\?[a-zA-Z]+:?", @"..\");
    return (cur + path.Substring(i + 1)).Replace(@"\\", @"\");
}

输出：

..\..\f\1.txt