public class PathUtil  
{  
    /// <summary>  
    /// Creates a relative path from one file  
    /// or folder to another.  
    /// </summary>  
    /// <param name="fromDirectory">  
    /// Contains the directory that defines the   
    /// start of the relative path.  
    /// </param>  
    /// <param name="toPath">  
    /// Contains the path that defines the  
    /// endpoint of the relative path.  
    /// </param>  
    /// <returns>  
    /// The relative path from the start  
    /// directory to the end path.  
    /// </returns>  
    /// <exception cref="ArgumentNullException"></exception>  
    public static string RelativePathTo(  
        string fromDirectory, string toPath)  
    {  
        if (fromDirectory == null)  
            throw new ArgumentNullException("fromDirectory");  
   
        if (toPath == null)  
            throw new ArgumentNullException("toPath");  
   
        bool isRooted = Path.IsPathRooted(fromDirectory)  
            && Path.IsPathRooted(toPath);  
   
        if (isRooted)  
        {  
            bool isDifferentRoot = string.Compare(  
                Path.GetPathRoot(fromDirectory),  
                Path.GetPathRoot(toPath), true) != 0;  
   
            if (isDifferentRoot)  
                return toPath;                           
        }                 
   
        StringCollection relativePath = new StringCollection();  
        string[] fromDirectories = fromDirectory.Split(  
            Path.DirectorySeparatorChar);  
   
        string[] toDirectories = toPath.Split(  
            Path.DirectorySeparatorChar);  
   
        int length = Math.Min(  
            fromDirectories.Length,  
            toDirectories.Length);  
   
        int lastCommonRoot = -1;  
   
        // find common root  
        for (int x = 0; x < length; x++)  
        {  
            if (string.Compare(fromDirectories[x],  
                toDirectories[x], true) != 0)  
                break;  
   
            lastCommonRoot = x;  
        }  
        if (lastCommonRoot == -1)  
            return toPath;  
   
        // add relative folders in from path  
        for (int x = lastCommonRoot + 1; x < fromDirectories.Length; x++)  
            if (fromDirectories[x].Length > 0)  
                relativePath.Add("..");  
   
        // add to folders to path  
        for (int x = lastCommonRoot + 1; x < toDirectories.Length; x++)  
            relativePath.Add(toDirectories[x]);  
   
        // create relative path  
        string[] relativeParts = new string[relativePath.Count];  
        relativePath.CopyTo(relativeParts, 0);  
   
        string newPath = string.Join(  
            Path.DirectorySeparatorChar.ToString(),  
            relativeParts);  
   
        return newPath;  
    }  
}