var domain = new List<string>();
        // MYSQL
        string serverName = "";
        string userName = "s";
        string dbName = "";
        string port = "";
        string password = "";
        string connStr = "server=" + serverName + ";user=" + userName + ";database=" + dbName + ";port=" + port + ";password=" + password + ";SslMode=none;";
        MySqlConnection conn = new MySqlConnection(connStr);
        string sql = "SELECT * FROM domain";
        MySqlCommand myCommand = new MySqlCommand(sql, conn);
        conn.Open();
        MySqlDataReader reader = myCommand.ExecuteReader();
        while (reader.Read())
            domain.Add(reader.GetString(0));
        conn.Close();


        string[] allLines = File.ReadAllLines(pathFile, Encoding.GetEncoding(1251));
        for (int i = 0; i < countline; i++ )
       {
            var re = File.ReadAllLines(pathFile, Encoding.Default).Where(s => !s.Contains(domain[i]));
         File.WriteAllLines("file.txt", re, Encoding.Default);
        }

var pathFile = @"D:ВЛАДtest.txt";//Тут Ваш путь
        var domain = new List<string>(); //Список с строками которых быть не должно
        string[] allLines = File.ReadAllLines(pathFile);//Файл изначально
        domain.Add("get");//Добавил для примера
        domain.Add("try");
        for (int i = 0; i < domain.Count; i++)
        {
            var re = File.ReadAllLines(pathFile, Encoding.Default).Where(s => !s.Contains(domain[i]));
            File.WriteAllLines(pathFile, re, Encoding.Default);
        }