public static void Main()
Console.WriteLine("---");
Console.WriteLine(System.IO.Path.GetExtension("https://approved.net/thing/thing2.html"));
Console.WriteLine(System.IO.Path.GetExtension("https://approved.net/thing/"));
Console.WriteLine(System.IO.Path.GetExtension("https://approved.net/thing/thing2.png/"));
Console.WriteLine(System.IO.Path.GetExtension("https://approved.net/thing/thing2.png"));
Console.WriteLine(System.IO.Path.GetExtension("https://approved.net/thing/"));
Console.WriteLine("---");