Question

I have a simple WCF service hosted in IIS7 using the HTTP protocol. The service contains a method which returns a custom object called Calendar. This object is very basic, and contains simple value-type properties, with the exception of one property, Holidays, which is of type List<IHoliday>. Holiday is again, a simple type comprised of value-type properties only.

The Calendar object is returned from the WCF service-method to an MVC controller, and is applied to a corresponding view. During memory-testing using dotTrace, it’s apparent that the Calendar object is finalised by the GC, but interestingly, its Holidays property, which is empty, remains on the heap.

It’s not a major performance-issue, taking up a mere 32 bytes, but I’m interested to know why the empty list is not disposed. I can provide code-samples, if necessary.

Source code and service configuration below:

public class Calendar : ICalendar
{
    [DataMember] private IEnumerable<IHoliday> holidays = new List<IHoliday>();
    [DataMember] private IEnumerable<IHolidayNotTaken> holidaysNotTaken = new List<IHolidayNotTaken>();
    [DataMember] private IEnumerable<INonInstructionalDay> nonInstructionalDays = new List<INonInstructionalDay>();
    [DataMember] private IEnumerable<ISchoolBreak> schoolBreaks = new List<ISchoolBreak>();
}

public class Holiday : IHoliday, IIdentifiable, IDisposable
{
    [DataMember(Name = @"date")] [JsonProperty(PropertyName = @"date")] private string date;

    [DataMember(Name = @"checked")]
    [JsonProperty(PropertyName = @"checked")]
    public bool Checked { get; set; }

    /// <summary>
    ///   Gets or sets the end Holiday Id.
    /// </summary>
    /// <value> The holiday id. </value>
    [DataMember(Name = @"id")]
    [JsonProperty(PropertyName = @"id")]
    public int HolidayId { get; set; }

    /// <summary>
    ///   Gets or sets the end description for the holiday.
    /// </summary>
    /// <value> The description. </value>
    [DataMember(Name = @"description")]
    [JsonProperty(PropertyName = @"description")]
    public string Description { get; set; }

    /// <summary>
    ///   Gets or sets the date of the holiday.
    /// </summary>
    /// <value> The holiday date. </value>
    [DataMember]
    [JsonIgnore]
    public DateTime Date { get; set; }

    /// <summary>
    ///   Gets or sets the sort order for the holiday.
    /// </summary>
    /// <value> The sort order. </value>
    [DataMember(Name = @"sortOrder")]
    [JsonProperty(PropertyName = @"sortOrder")]
    public int SortOrder { get; set; }

    /// <summary>
    ///   Gets the <see cref="IIdentifiable.Type" /> of this instance.
    /// </summary>
    [DataMember(Name = @"type")]
    [JsonProperty(PropertyName = @"type")]
    public string Type { get; private set; }

    /// <summary>
    ///   Invoked when this instance is serialising.
    /// </summary>
    /// <param name="streamingContext"> The streaming context. </param>
    [OnSerializing]
    private void OnSerialising(StreamingContext streamingContext)
    {
        date = Date.ToString(@"yyyy-MM-dd");
        Type = GetType().ToString();
    }
}

Service Method:

public Domain.Calendar GetCalendarByMember(string externalId)
    {
        try
        {
            using (var e = new EPlannerEntities())
            {
                var memberId = e.Members
                    .Where(m => m.ExternalId == externalId)
                    .Select(m => m.MemberId)
                    .SingleOrDefault();

                if (memberId.Equals(0))
                {
                    e.Members.AddObject(new Member { ExternalId = externalId.Trim() });

                    var calendar = new Domain.Calendar
                                   {
                                       DefaultViewId = 2,
                                       MemberId = memberId,
                                       IsWeekendsVisible = true,
                                       TimeFormatId = 1,
                                       DayBeginTime = new TimeSpan(0, 8, 0, 0),
                                       DayEndTime = new TimeSpan(0, 16, 0, 0),
                                       DateFormatId = 1
                                   };

                    e.Calendars.AddObject(calendar);
                    e.SaveChanges();

                    return calendar;
                }

                return e.Calendars.Single(c => c.MemberId == memberId);
            }
        }
        catch (Exception exception)
        {
            throw ErrorManager.FaultException(ExceptionType.Business, (int) CalendarErrorCodes.GeneralError, exception);
        }
    }

Service Configuration:

<services>
  <service behaviorConfiguration="CalendarServiceBehavior" name="HMH.ePlanner.Services.Calendar">
    <endpoint address="" binding="netTcpBinding" bindingConfiguration="TCPBinding" name="TCPEndPoint" contract="HMH.ePlanner.Services.ICalendar">
      <identity>
        <dns value="localhost" />
      </identity>
    </endpoint>
    <endpoint address="" binding="basicHttpBinding" bindingConfiguration="HTTPBinding" name="HttpEndPoint" contract="HMH.ePlanner.Services.ICalendar" />
    <endpoint address="mex" binding="mexTcpBinding" bindingConfiguration="" name="TCPMexEndPoint" contract="IMetadataExchange" />
    <host>
      <baseAddresses>
        <add baseAddress="net.tcp://localhost:808/Calendar.svc" />
      </baseAddresses>
    </host>
  </service>
</services>

Answer 1

The problem stems from the fact that the Holiday list is instantiated without specifying an UpperBound. Specifying an UpperBound ensures that the object is removed from the Heap after garbage-collection.