using System;

public class Program

{

    public static void Main(string[] args)

    {

        Console.WriteLine("223232-1.jpg".GetUntilOrEmpty());

        Console.WriteLine("443-2.jpg".GetUntilOrEmpty());

        Console.WriteLine("34443553-5.jpg".GetUntilOrEmpty());

        Console.WriteLine("344-5-3.jpg".GetUntilOrEmpty());

        Console.WriteLine("3443.jpg".GetUntilOrEmpty());

        Console.WriteLine("34-43.jpg".GetUntilOrEmpty());

    }

}

​

static class Helper

{

    public static string GetUntilOrEmpty(this string text, string stopAt = "-")

    {

        if (!String.IsNullOrWhiteSpace(text))

        {

            int charLocation = text.IndexOf(stopAt, StringComparison.Ordinal);

            if (charLocation > 0)

            {

                return text.Substring(0, charLocation);

            }

        }

        return String.Empty;

    }

}