using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		var input = "35afe06d-8393-4559-b6d7-74d35ce131d8|Master";
        var pattern = @"([a-f0-9]+(?:-[a-f0-9]+){4})\|(\w+)";
        var replacement = "http://my-server/media/guid/$1?v=$2";
        var output = Regex.Replace(input, pattern, replacement);
        Console.WriteLine(output);
	}
}