ReadWrite.cs

static void Main(string[] args) {

        var text = File.ReadAllLines(@"C:\Users\jpor01\dev\grh.txt");
        var file = new StreamWriter(@"C:\Users\jpor01\dev\grh-out.txt", true);
        
        foreach (string line in text)
        {
            var pattern = Regex.IsMatch(line, @"\b(0x00000005)\b", RegexOptions.IgnoreCase );

            if (pattern == true)
            {
                file.WriteLine(line);
            }
        }
     
            // Keep the console window open in debug mode.
        Console.WriteLine("Press any key to exit.");
        file.Close();
        System.Console.ReadKey();
        }