public SearchService(string connectionString, SearchServiceConfiguration configuration)
     : base(connectionString)
 {
     if (configuration == null) throw new ArgumentNullException("configuration");
     _config = configuration;
     _connectionString = connectionString;
 }
 static SearchServiceConfiguration()
 {
     Default = new SearchServiceConfiguration
     {
         ElasticsearchNode = ConfigurationManager.AppSettings["es:node"] ?? @"http://*****:*****@"hinata"
     };
 }