Question

When I return IEnumerable<ProgramRange> an exception is thrown:

The underlying connection was closed: The connection was closed unexpectedly.

The class ProgramRange looks like this:

[DataContract]
public partial class ProgramRange
{
    public ProgramRange()
    {
        this.GradeVariants = new HashSet<GradeVariant>();
    }

    [DataMember]
    public int ID { get; set; }
    [DataMember]
    public int Range { get; set; }
    [DataMember]
    public string Description { get; set; }

    [DataMember]
    public virtual ICollection<GradeVariant> GradeVariants { get; set; }
}

The collection only contains eight items, so I don’t think it’s the <dataContractSerializer maxItemsInObjectGraph="2147483647" /> which is often suggested.

When I fetch the data from the context I do .ToList() so it can’t be that:

 public IEnumerable<ProgramRange> GetAll()
    {
        using (Entities dbContext = new Entities())
        {
            return dbContext.ProgramRanges.ToList();

        }
    }

I’ve tried to add the ProgramRange class to the known types of your service in the implementation:

 [ServiceBehavior]
 [ServiceKnownType(typeof(ProgramRange))]
 public class ValidationService : IValidationService

I’ve tried returning several other things just to test: ProgramRange (works), IEnumerable<string> (works), List<ProgramRange> (does’t work)

I know there are several question on the subject here on stackowerflow and I tried a lot of suggestions, but I can’t get it to work.

Edit:

Here’s the GradeVariant class:

[DataContract]
public partial class GradeVariant
{
    public GradeVariant()
    {
        this.GradeVariantRules = new HashSet<GradeVariantRule>();
    }

    [DataMember]
    public int ID { get; set; }
    [DataMember]
    public int GradeTypeID { get; set; }
    [DataMember]
    public int ProgramRangeID { get; set; }
    [DataMember]
    public Nullable<int> ProgramID { get; set; }
    [DataMember]
    public Nullable<int> ApprenticeID { get; set; }
    [DataMember]
    public Nullable<int> Prefix { get; set; }
    [DataMember]
    public Nullable<bool> IV { get; set; }
    [DataMember]
    public string Description { get; set; }

    [DataMember]
    public virtual GradeType GradeType { get; set; }
    [DataMember]
    public virtual ProgramRange ProgramRange { get; set; }
    [DataMember]
    public virtual ICollection<GradeVariantRule> GradeVariantRules { get; set; }
}

Answer 1

I found the answer to my own question and here goes:

The problem was that WCF was unable to serialize the circular reference that Entity Framework created when loading the referenced entities.

To resolve this issue, simply put

[DataContract(IsReference = true)]

over the model class.

It’s explained in detail here, http://www.binaryforge-software.com/wpblog/?p=129