using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        var str = "Npgsql.PostgresException (0x80004005): 42P01: relation \"dataset_25635dd6f46642b3a934460cf6d1de4b\" does not exist";

        var match = Regex.Match(str, "dataset_([a-f0-9]{32})");

        if(match.Success)

        {

            var uuidStr = match.Groups[1].Value;

            Console.WriteLine(uuidStr);

            if (Guid.TryParse(uuidStr, out var datasetId))

                Console.WriteLine(datasetId);

            else

                Console.WriteLine("no parse uuid");

        }

        else

            Console.WriteLine("no success");

    }

}