IQueryable<> Serialization - C#-VS2008-WCF

Question

I built my *.dbml file with the required tables and that generated the relationships, 1 to many.

One of my methods in my WCF Service library has this query

 IQueryable<Client>localClient = from c in db.Clients
              where c.ClientID.Equals(2612)
              select c;

 foreach(Client currentClient in localClient)
 {
    //Call serialize method here
 }

One of the table which client has a 1 to many relationships is Client - Employee

With 'localClient', I want to serialize that and return to the invoker. However it tells me that the the XML document could not be formed.

This is the InnerException: A circular reference was detected while serializing an object of type TestDB_Public.Employee.

My serialization code

    public string Serialize(object o, XmlSerializerNamespaces ns)
    {
        try
        {
            System.IO.MemoryStream m = new System.IO.MemoryStream();

            if (ns != null)
                serializer.Serialize(m, o, ns);
            else
                serializer.Serialize(m, o);

            m.Position = 0;
            byte[] b = new byte[m.Length];
            m.Read(b, 0, b.Length);

            return System.Text.UTF8Encoding.UTF8.GetString(b);
        }
        catch (Exception ex)
        {
            return "Ex = " + ex.ToString();
        }
    }

Is serialization of IQueryable<> with 1 to many relationships not possible?

Answer 1

What exactly is the error message? Note that you have to serialize something concrete like a list or array of objects (not a query).

If you want queryable over the wire, look at ADO.NET Data Services, which does this.

Also - have you set the serialization mode to "unidirectional" in the dbml designer? As long as there are no loops, it should work fine.

Answer 2

Marc: For some reason it is not allowing me to add a comment;

I added this

[Table(Name="dbo.Client")]
[DataContract(IsReference=true)]
public partial class Client: INotifyPropertyChanging, INotifyPropertyChanged
{
  ..//
  private EntitySet<ClEmp> _ClEmp;

  [Association(N...)]
  [DataMember(Order=70, EmitDefaultValue=false)]
  public EntitySet<ClEmp> ClEmps
}

My serialization is this:

DataContractSerializer ser =
                    new DataContractSerializer(typeof(Client));
                var ms = new System.IO.MemoryStream();

                ser.WriteObject(ms, r);

                ms.Seek(0, System.IO.SeekOrigin.Begin);



                var sr = new System.IO.StreamReader(ms);

                var xml = sr.ReadToEnd();

when i look at var xml, i do not get my enity set ClEmp.

Answer 3

You can't serialise an object graph that has cyclical relationships:

class Employee
{
  Employee Manager;
  List<Employee> Employees;


}


var bossMan = new Employee();
var emp2 = new Employee{Manager = bossMan}
var bossMan.Employees.Add(emp2);

If you now try to serialise bossman or emp2, you will get the exception.

Have a look at this post, check the Cyclic Object Graphs for a solution.