public AdoNetContext(string providerName, string connectionString)
        {
            _providerName     = providerName;
            _connectionString = connectionString;

            _factory = DbProviderFactories.GetFactory(providerName);
            _dialect = GetSqlDialect();
        }
        public AdoNetContext(string connectionName)
        {
            _providerName     = ConfigurationManager.ConnectionStrings[connectionName].ProviderName;
            _connectionString = ConfigurationManager.ConnectionStrings[connectionName].ConnectionString;

            _factory = DbProviderFactories.GetFactory(_providerName);
            _dialect = GetSqlDialect();
        }
        public AdoNetContext(DbProviderFactory factory, string providerName, string connectionString)
        {
            _providerName     = providerName;
            _connectionString = connectionString;

            _factory = factory;
            _dialect = GetSqlDialect();
        }