http://pt.stackoverflow.com/questions/84200/express%C3%A3o-regular-pegando-n%C3%BAmeros-entre-dois-textos-pr%C3%A9-definidos

CSharp · Console

/Program.cs

using System;
using System.Text.RegularExpressions;
					
public class Program
{	
	public static void Main()
	{
		var re = new Regex(@"/(\d+)(?=-)");
		var match = re.Match("http://www.meudominio.com/1789519-texto");
		Console.WriteLine(match.Groups[1]);
	}
}