How to get the relative path?

Questions & Answers
1

I have a test class to get the relative path
using System;
using System.IO;
using UnityEngine;
using System.Collections;

public class testType : MonoBehaviour
{

    // Use this for initialization
	void Start ()
	{
        Out(@"D:\Data", @"D:\Data\Mail");
        Out(@"", @"D:\Data\Mail");
        Out(@"D:\Data", @"");
        Out(@"D:\Data", @"C:\ICQ\Traf");
        Out(@"D:\Project\King\Assets", @"D:\Project\King\Assets\Test");
        Out(@"D:\Project\King\Assets", @"D:\Project\Lolo");
    }

	void Out(string path, string path2)
    {
        Debug.Log(string.Format("Path1 : {0}

Path2 : {1}
Relative : "{2}"", path, path2 ,RelativePath(path, path2)));
}

    public string RelativePath(string fromPath, string toPath)
    {
        if (String.IsNullOrEmpty(toPath)) return "";
        if (String.IsNullOrEmpty(fromPath)) return toPath;

        toPath = toPath.Replace(Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar);// + Path.DirectorySeparatorChar;
        fromPath = fromPath.Replace(Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar);// + Path.DirectorySeparatorChar;
        if (fromPath[fromPath.Length - 1] != Path.DirectorySeparatorChar) fromPath += Path.DirectorySeparatorChar;
        Uri fromUri = new Uri(fromPath);
        Uri toUri = new Uri(toPath);

        if (fromUri.Scheme != toUri.Scheme) { return toPath; } // path can't be made relative.

        Uri relativeUri = null;
        try
        {
            relativeUri = fromUri.MakeRelativeUri(toUri);
        }
        catch
        {
            relativeUri = toUri;
        }
        string relativePath = Uri.UnescapeDataString(relativeUri.ToString());

        if (toUri.Scheme.ToUpperInvariant() == "FILE")
        {
            relativePath = relativePath.Replace(Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar);
        }

        return relativePath;
    }
}

But not always return the right path:

Path1 : "D:\Data"
Path2 : "D:\Data\Mail"
Relative : "Mail"

Path1 : "" 
Path2 : "D:\Data\Mail"
Relative : "D:\Data\Mail"

Path1 : "D:\Data"
Path2 : "" 
Relative : ""

Path1 : "D:\Data"
Path2 : "C:\ICQ\Traf"
Relative : "file:\\\C:\ICQ\Traf"

Path1 : "D:\Project\King\Assets"
Path2 : "D:\Project\King\Assets\Test"
Relative : "Test"

Path1 : "D:\Project\King\Assets"
Path2 : "D:\Project\Lolo"
Relative : "..\Lolo"

Error in tests 4 and 6. Help to understand what went wrong.
Windows 7, Unity 4.6

2

Error 4 into

catch
         {
             relativeUri = toUri;
         }

need

catch
        {
            return toUri.LocalPath;
        }