/// <summary>
/// 执行SQL语句。
/// </summary>
/// <param name="commandText">SQL字符串。</param>
/// <param name="commandType">SQL类型。</param>
/// <param name="parameters">参数匿名类型。</param>
/// <param name="cancellationToken">取消标记。</param>
/// <returns>返回单一结果实例对象。</returns>
public Task <object> ExecuteScalarAsync(string commandText, object parameters = null, CommandType commandType = CommandType.Text,
CancellationToken cancellationToken = default)
=> _executor.ExecuteScalarAsync(commandText, parameters, commandType, cancellationToken);
