小弟最近面试遇到一个题目，一个关于客户旅行行程的类，有一些操作，包括一些异步操作。
要求找出其中写的不好的地方，并提出改进方案

根据好的编码标准和设计，检查以下代码，这是部分实现的一个行程计划。指出您可以在代码中看到的任何问题(如果有的话)，以及应该做些什么来改进它们。

/// <summary>
/// Provides capabilities for managing a customers itinerary.
/// </summary>
public class ItineraryManager
{
private readonly IDataStore _dataStore;
private readonly IDistanceCalculator _distanceCalculator;

public ItineraryManager()
{
    _dataStore = new SqlAgentStore(ConfigurationManager.ConnectionStrings["SqlDbConnection"].ConnectionString);
    _distanceCalculator = new GoogleMapsDistanceCalculator(ConfigurationManager.AppSettings["GoogleMapsApiKey"]);
}

/// <summary>
/// Calculates a quote for a customers itinerary from a provided list of airline providers.
/// </summary>
/// <param name="itineraryId">The identifier of the itinerary</param>
/// <param name="priceProviders">A collection of airline price providers.</param>
/// <returns>A collection of quotes from the different airlines.</returns>
public IEnumerable<Quote> CalculateAirlinePrices(int itineraryId, IEnumerable<IAirlinePriceProvider> priceProviders)
{
    var itinerary = _dataStore.GetItinaryAsync(itineraryId).Result;
    if (itinerary == null)
        throw new InvalidOperationException();

    List<Quote> results = new List<Quote>();
    Parallel.ForEach(priceProviders, provider =>
    {
        var quotes = provider.GetQuotes(itinerary.TicketClass, itinerary.Waypoints);
        foreach (var quote in quotes)
            results.Add(quote);
    });
    return results;
}

/// <summary>
/// Calculates the total distance traveled across all waypoints in a customers itinerary.
/// </summary>
/// <param name="itineraryId">The identifier of the itinerary</param>
/// <returns>The total distance traveled.</returns>
public async Task<double> CalculateTotalTravelDistanceAsync(int itineraryId)
{
    var itinerary = await _dataStore.GetItinaryAsync(itineraryId);
    if (itinerary == null)
        throw new InvalidOperationException();
    double result = 0;
    for(int i=0; i<itinerary.Waypoints.Count-1; i++)
    {
        result = result + _distanceCalculator.GetDistanceAsync(itinerary.Waypoints[i],
             itinerary.Waypoints[i + 1]).Result;
    }
    return result;
}

/// <summary>
/// Loads a Travel agents details from Storage
/// </summary>
/// <param name="id">The id of the travel agent.</param>
/// <param name="updatedPhoneNumber">If set updates the agents phone number.</param>
/// <returns>The travel agent if located, otherwise null.</returns>
public TravelAgent FindAgent(int id, string updatedPhoneNumber)
{
    var agentDao = _dataStore.GetAgent(id);
    if (agentDao == null)
        return null;
    if (!string.IsNullOrWhiteSpace(updatedPhoneNumber))
    {
        agentDao.PhoneNumber = updatedPhoneNumber;
        _dataStore.UpdateAgent(id, agentDao);
    }
    return Mapper.Map<TravelAgent>(agentDao);
}

}