using System;

                using System.Text.RegularExpressions;   

public class Program

{

    public static void Main()

    {

        var baseAddress = "https://cdn1.ozone.ru/s3";

        var pattern = $"^{baseAddress}/[^'\"<>]+?\\.(jpg|jpeg|png)$";

        Console.WriteLine(Regex.IsMatch($"https://cdn1ru/s3/rms/{Guid.NewGuid()}.jpg", pattern));

    }

    public class A

    {

        public B BField {get;set;}

    }

    public class B

    {

        public bool Field{ get;set;}

    }

}