using System;
using System.IO;

public class Test
{
	public static void Main()
	{
		string path = @"photo\myFolder\image.jpg";
                string file = Path.GetFileNameWithoutExtension(path);
                string NewPath = path.Replace(file, file + "-resize");
                Console.WriteLine(NewPath); //photo\myFolder\image-resize.jpg
	}
}