Since no TimeZoneInfo in SL, created Domain Data Service: ComplexType issue.

Question

Hello,

Our Silverlight 5 RIA application needs to present a list of TimeZoneInfo objects to the user, so he/she can select a particular timezone, which is stored in the database and used for some mapping functions.  Unfortunately, Silverlight does not provide TimeZoneInfo.GetSystemTimeZones() nor many of the related functions from .NET, so I am trying to create operations in a domain data service (TimeZoneDDS) to provide these function from the server.  I know that there are a lot of ways to deal with TimeZone information, but this is the method that we must use in this project. 

Right now, I am trying to return the list from TimeZoneInfo.GetSystemTimeZones(), but am hitting an error.  Unfortunately, I am receiving an error that seems to indicate that RIA is not happy about returning a list of TimeZoneInfo objects.  From my research on the Net, the latest version of RIA supports complex objects, so I am at a loss as to how to fix this issue.  I would appreciate your help in tweaking the following code so it will work.  I am sure that this posting will help others who need to accomplish this same kind of task.

ERROR:
Operation named 'GetSystemTimeZones' does not conform to the required signature. Return types must be an entity or complex type, a collection of entities or complex types, or one of the predefined serializable types.

Thank you for your time and help,

Mike

SILVERLIGHT CLIENT:
            InvokeOperation<IEnumerable<TimeZoneInfo>> io = context.GetSystemTimeZones();
            io.Completed += (s1, ea1) =>
            {
                if (!io.HasError && !io.IsCanceled)
                {  
                    timeZoneLookUpEdit.ItemsSource = io.Value;
                }
            };

DOMAIN SERVICE:
        /// <summary>
        /// Provides a list of all the TimeZoneInfo objects from the server.
        /// </summary>
        /// <remarks>Silverlight does not provide this functionality,
        /// so this method provides the list of TimeZoneInfo objects
        /// that the server contains.  These can be used by the application.</remarks>
        /// <returns>List of TimeZoneInfo objects, which can be empty.</returns>
        [Invoke]
        public List<TimeZoneInfo> GetSystemTimeZones()
        {
            ReadOnlyCollection<TimeZoneInfo> tzi = TimeZoneInfo.GetSystemTimeZones();
            return (tzi == null) ? new List<TimeZoneInfo>() : tzi.ToList<TimeZoneInfo>();
        }

Answer 1

I couldn't figure out how to return a list of TimeZoneInfo items (complex type), so I created my own lightweight class that contained the bare minimum that I needed: Id and Display name.  I used it to serialize what was needed from the DDS to the client. 

I still would love to learn why I couldn't pass back a list of TimeZoneInfo objects, but at least I have a work-around that works.

/////////////////////////////////////

    [Serializable]
    public class AbohTimeZoneInfo
    {
        /// <summary>
        /// A friendly version of the time zone name.
        /// </summary>
        public string DisplayName { get; private set; }

        [Key]
        // The unique id assigned to the time zone.
        public string Id { get; private set; }

        /// <summary>
        /// Constructor
        /// </summary>
        public AbohTimeZoneInfo()
        {
            Id = string.Empty;
            DisplayName = string.Empty;
        }

        /// <summary>
        /// Constructor
        /// </summary>
        /// <param name="tzi">A TimeZoneInfo</param>
        public AbohTimeZoneInfo(TimeZoneInfo tzid)
        {
            Id = tzid.Id;
            DisplayName = tzid.DisplayName;
        }
    }

//////////////////////////// DDS /////////////////////////

         [Query]
         public List<AbohTimeZoneInfo> GetSystemTimeZones()
        {
             List<AbohTimeZoneInfo> list = new List<AbohTimeZoneInfo>();
             foreach(TimeZoneInfo tzi in TimeZoneInfo.GetSystemTimeZones())
             {
                 list.Add(new AbohTimeZoneInfo(tzi));
             }

             return list;
         }

///////////////////////////////// CLIENT ////////////////

LoadOperation<AbohTimeZoneInfo> lo = tzContext.Load(tzContext.GetSystemTimeZonesQuery());
        lo.Completed += (s, ea) =>
        {
            if (!lo.HasError && !lo.IsCanceled)
            {
                foreach (AbohTimeZoneInfo p in lo.Entities)
                {
                    ;
                }
            }
        };