5

I am learning about web services and the book I am using is pulling data from SQL server using the entity framework (which I know little about too).

Unfortunately the classes created by the entity framework contain things like:

public Conference()
{
   this.Sessions = new HashSet<Session>();
}
public virtual ICollection<Session> Sessions { get; set; }

Which causes a problem because an interface is not serialisable:

Cannot serialize member X of type System.Collections.Generic.ICollection ... because it is an interface.

Now I could (and did) modify the generated classes to use concrete classes but if I ever need to regenerate the entities then that change will be undone. Ideally I could tell the entity framework to generate something like this (or even better, have control of the concrete type so I could tell the entity framework to use a List if I want to):

public Conference()
{
   this.Sessions = new HashSet<Session>();
}
public virtual HashSet<Session> Sessions { get; set; }

Is it possible? If so, how?

Julien Rousseau
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    This has some related discussion http://stackoverflow.com/questions/1333864/xml-serialization-of-interface-property – ta.speot.is Jul 12 '13 at 23:57
  • It's a bit more complicated than what I was thinking of (I didn't need to use an interface for that exercise) but it's interesting and informative so thanks for it. I haven't had time to look at it in details but I think a code-first approach and mapping to an existing database looks like a viable approach for what I was thinking of: http://msdn.microsoft.com/en-us/data/jj200620.aspx – Julien Rousseau Jul 14 '13 at 22:11

2 Answers2

0

EF code generator creates entity classes as partial, so you may create another code file in the same assembly with some tricks:

public partial class Conference
{
    [XmlIgnore]
    public bool SessionsSpecified
    {
        get { return false; }
    }

    public Session[] SerializableSessions
    {
        get { return new Sessions.ToArray(); }
        set { Sessions = value; }
    }
}

SessionSpecified property is a XmlSerializer trick to ignore Sessions property during serialization. Session[] will be serialized instead of ICollection. Check if it is possible to expose internal EF collection types to use cast instead of copying an array.

Alternative solution is to implement IXmlSerializable and have a full control of how Conference class serialized.

Volodymyr Dombrovskyi
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I used T4 template.

In the template, I changed ICollection to List, and added [Serializable] to entity types and complex types.

I also had to disable proxy type generation:

((IObjectContextAdapter)entities).ObjectContext.ContextOptions.ProxyCreationEnabled = false;
Hogan
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