WCF Data Service Query error

Question

Hi,

I would like to filter the properties I return from the WCF Data Service but I am getting the error below:

Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>' to 'System.Collections.ObjectModel.Collection<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>'. An explicit conversion exists (are you missing a cast?) 

This is the code I have used. Could someone please shed some light on how I can achieve this:

LabellerDataServiceRef.DocketHubEntities ctx = new LabellerDataServiceRef.DocketHubEntities(new Uri(@"http://localhost:2332/LabellerDataService.svc", UriKind.RelativeOrAbsolute));

        public IEnumerable<SiteClient> GetSiteClient()
        {
            var companies = (from sc in ctx.SiteClients.Expand("SiteClientMailing")
                             orderby sc.ClientName
                             select new SiteClient
                             {
                                 SiteClientID = sc.SiteClientID,
                                 ClientName = sc.ClientName,
                                 SiteClientMailings = (from m in sc.SiteClientMailings
                                                        orderby m.ClientName
                                                        select new SiteClientMailing
                                                        {
                                                            ClientName = m.ClientName,
                                                            PlannedMailingDate = m.PlannedMailingDate

                                                        })
                             });

Cheers

C

Answer 1

There are three problems with your query:

1) WCF DS Client doesn't support orderby in the expansion. So the orderby you specified for the SiteClientMailings will not work.

2) The error comes from the C# compiler which is complaining that your SiteClientMailings property is Collection<T> but you're assigning an IEnumerable<T> to it. I think just a simple cast might solve this problem.

3) Since you prescribed the shape of the result using select statements, the usage of Expand() method is not needed and I think it will also cause failures.

Thanks,

---

Vitek Karas [MSFT]

Answer 2

Hi Vitek,

Thanks for your help.

2 - Could you please show me where and how to cast it?

3 - I think the expand is causing problems as you mentioned but how can I get all the child SiteClientMailings if I do not use expand? Please also note that I am trying to limit the properties returned by the method.

Cheers

C

Answer 3

2 - Just add (Collection<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>) in front of your inner query (from ...).

3 - The fact that you have an inner query for the SiteClientMailings will tell the LINQ translator to expand it already.

Thanks,

---

Vitek Karas [MSFT]

Answer 4

Hi Vitek,

Thanks again. I will try this tomorrow since I do not have the computer with me at the moment.

I will let you know how I get on.

I had an idea but I would like your suggestion to see if this is the right approach. Would that be better if I created a ?

I have tried creating a custom model to encapsulate the EF model where I return only one properties of Department - ID but also return some properties of the related Employees that are in that departmet.

However, I get an error to do with Data services not liking complex properties.

Is it possible to achive what I need?

[DataServiceKey(ID)]
public class DepartmentModel
{

  public int ID { get; set; }
  public IQueryable<EmployeeModel> Employees

}

[DataServiceKey(ID)]
public class EmployeeModel
{
  public int ID { get; set; }
  public string FirstName { get; set; }
}

public class DataModel
{
  public DataModel()
  {
    using (var dbContext = new ODataDemoEntities())
    {
      Departments = from d in dbContext.Departments
                    select new DepartmentModel
                    {
                      ID = d.DepartmentID,
                      Employees = (from e in d.Employees
                            select new EmployeeModel
                            {
                               ID = e.EmployeeID,
                               FirstName = e.FirstName
                            }
                      )
                    };

  public IQueryable<EmployeeModel> Employees { get; private set; }
  public IQueryable<DepartmentModel> Departments { get; private set; }
}

Cheers

C

Answer 5

I don't see anything particularly wrong with the above. Could you please post the exception along with its callstack when you get a chance?

Thanks,

---

Vitek Karas [MSFT]

Answer 6

Hi Vitek,

How are you?

I have casted the inner query as you suggested but I get another error during run time:

Error translating Linq expression to URI: Initializing instances of the entity type LabellerWebTest.LabellerDataServiceRef.SiteClient with the expression Convert(sc.SiteClientMailings.Select(m => new SiteClientMailing() {ClientName = m.ClientName, PlannedMailingDate = m.PlannedMailingDate})) is not supported.}

I am posting below my Test Repository class that calls the WCF Data Service and the WCF Data Service. Could you spot anything could be causing this error?

I did not realise it was so difficult to flat the objects and limit the number of properties returned by WCF Data Services :-)

Cheers

TestRepository

 public class TestRepository : ILabellerRepositoryDataService, IDisposable
 {
         LabellerDataServiceRef.DocketHubEntities ctx = new LabellerDataServiceRef.DocketHubEntities(new Uri(@"http://localhost:2332/LabellerDataService.svc", UriKind.RelativeOrAbsolute));

 
        public IEnumerable<LabellerDataServiceRef.SiteClient> GetSiteClient()
        {
            var companies = (from sc in ctx.SiteClients
                             select new LabellerDataServiceRef.SiteClient
                             {
                                 SiteClientID = sc.SiteClientID,
                                 ClientName = sc.ClientName,
                                 SiteClientMailings =
                                 (Collection<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>)(from m in sc.SiteClientMailings
                                                select new LabellerDataServiceRef.SiteClientMailing
                                                {
                                                    ClientName = m.ClientName,
                                                    PlannedMailingDate = m.PlannedMailingDate

                                                })
                             });

            return companies;
        }      

        public void Dispose()
        {
            throw new NotImplementedException();
        }
}

WCF Data Service

 [System.ServiceModel.ServiceBehavior(IncludeExceptionDetailInFaults = true)]
  public class LabellerDataService : DataService<DocketHubEntities>
  {
        public static void InitializeService(DataServiceConfiguration config)
        {
             config.SetEntitySetAccessRule("*", EntitySetRights.AllRead);
             config.SetServiceOperationAccessRule("*", ServiceOperationRights.All);
             config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2;

             config.UseVerboseErrors = true;

             config.MaxBatchCount = 40;
           
        }
}

Answer 7

Any help? Thanks

C

Answer 8

Hi Claudio,

 Change your code to be :

 var companies = (from sc inctx.SiteClients
                             select new LabellerDataServiceRef.SiteClient
                             {
                                 SiteClientID = sc.SiteClientID,
                                 ClientName = sc.ClientName,
                                 SiteClientMailings = new List<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>(
                                               from m in sc.SiteClientMailings
                                                select new LabellerDataServiceRef.SiteClientMailing
                                                {
                                                    ClientName = m.ClientName,
                                                    PlannedMailingDate = m.PlannedMailingDate
                                                })
                             });

---

Phani Raj Astoria http://blogs.msdn.com/PhaniRaj

Answer 9

Hi Phani Raj,

Thanks for your reply and sample code. Unfortunately I get this error when I try  you code?

Cannot implicitly convert type 'System.Collections.Generic.List<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>' to 'System.Collections.ObjectModel.Collection<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>'

Do you have any ideas what I have to do to fix it?

Cheers

New Code Below
--------------------

LabellerDataServiceRef.DocketHubEntities ctx = new LabellerDataServiceRef.DocketHubEntities(new Uri(@"http://localhost:2332/LabellerDataService.svc", UriKind.RelativeOrAbsolute));

public IEnumerable<LabellerDataServiceRef.SiteClient> GetSiteClient()
{
            var companies = (from sc in ctx.SiteClients
                             select new LabellerDataServiceRef.SiteClient
                                        {
                                            SiteClientID = sc.SiteClientID,
                                            ClientName = sc.ClientName,
                                            SiteClientMailings =
                                                new List<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>(
                                                from m in sc.SiteClientMailings
                                                select new LabellerDataServiceRef.SiteClientMailing
                                                           {
                                                               ClientName = m.ClientName,
                                                               PlannedMailingDate = m.PlannedMailingDate
                                                           })
                                        });
            return companies;
}

Answer 10

Hi Claudio,

 I didn't know that the left hand side type was Collection<T>,

 try changing the property assignment to be : 

SiteClientMailings =
                                              new Collection<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>(  new List<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>(
                                                from m in sc.SiteClientMailings
                                                select new LabellerDataServiceRef.SiteClientMailing
                                                           {
                                                               ClientName = m.ClientName,
                                                               PlannedMailingDate = m.PlannedMailingDate
                                                           }) )

This way, you use the constructor of Collection<T> which takes a List<T> instance.

---

Phani Raj Astoria http://blogs.msdn.com/PhaniRaj

Answer 11

Hi Phani Raj,

Sorry for the long time I took to anwser back but I have finally had time to have a look at it.

I tried your new sample code and got this error message:

"
Initializing instances of the entity type LabellerWebTest.LabellerDataServiceRef.SiteClient with the expression new Collection`1(new List`1(sc.SiteClientMailings.Select(m => new SiteClientMailing() {ClientName = m.ClientName, PlannedMailingDate = m.PlannedMailingDate}))) is not supported.

"

Do you have any ideas why I am getting this message? Is there a way to fix it?

Cheers

This is the full code:

 LabellerDataServiceRef.DocketHubEntities ctx = new LabellerDataServiceRef.DocketHubEntities(new Uri(@"http://localhost:2332/LabellerDataService.svc", UriKind.RelativeOrAbsolute));

public IEnumerable<LabellerDataServiceRef.SiteClient> GetSiteClient()
{
          
            var companies = (from sc in ctx.SiteClients
                             select new LabellerDataServiceRef.SiteClient
                                        {
                                            SiteClientID = sc.SiteClientID,
                                            ClientName = sc.ClientName,
                                            SiteClientMailings =  new Collection<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>
                                                (new List<LabellerWebTest.LabellerDataServiceRef.SiteClientMailing>
                                                    (
                                                
                                                from m in sc.SiteClientMailings
                                                select new LabellerDataServiceRef.SiteClientMailing
                                                           {
                                                               ClientName = m.ClientName,
                                                               PlannedMailingDate = m.PlannedMailingDate
                                                           }))
                                        });
            return companies;
}