实体未使用DataContractSerializer进行序列化

Question

I am trying to serialize Entities in my project. I have a lot of them so i'm starting with just one at the moment. The goal of my project is to create an audit trail with entity framework. When I break at audit.newvalue = doc.root.tostring() the root is null. I've been trying to follow every tutorial or q/ai find related to doing this, but everytime i get null. Not sure what i'm missing here.

[DataContract(IsReference=true)]
public class Client
{
    [DataMember]
    [Key]
    [DatabaseGenerated(System.ComponentModel.DataAnnotations.DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [DataMember]
    public bool Active { get; set; }

    [DataMember]
    [Required]
    public string LastName { get; set; }
    [DataMember]
    public string MiddleName { get; set; }
    [DataMember]
    [Required]
    public string FirstName { get; set; }

    [DataMember]
    [Required]
    public DateTime BirthDate { get; set; }
}

private Audit.DBAudit AuditTrailFactory(ObjectStateEntry entry, string userName)
    {
        var oc = this as IObjectContextAdapter; ;
        oc.ObjectContext.DetectChanges();

        Audit.DBAudit audit = new Audit.DBAudit();
        audit.TimeStamp = DateTime.Now;
        audit.Entity = entry.EntitySet.Name;
        audit.User = userName;

        // set action type
        switch (entry.State)
        {
            case System.Data.EntityState.Added:
                audit.ActionType = ActionTypes.I.ToString();
                break;
            case System.Data.EntityState.Modified:
                audit.ActionType = ActionTypes.U.ToString();
                break;
            case System.Data.EntityState.Deleted:
                audit.ActionType = ActionTypes.D.ToString();
                break;
            default:
                audit.ActionType = "F"; // fubar
                break;
        }

        DataContractSerializer serializer = new DataContractSerializer(entry.Entity.GetType());

        XDocument doc = new XDocument();
        XmlWriter writer = doc.CreateWriter();

        serializer.WriteObject(writer, entry.Entity);
        audit.NewValue = doc.Root.ToString();

        return audit;
    }

    [TestMethod]
    public void CanCreateAudit()
    {
        FircrestModel.Client.Client client = new FircrestModel.Client.Client
        {
            FirstName = "billy",
            LastName = "jones",
            BirthDate = new DateTime(1970, 1, 1),
        };

        context.Clients.Add(client);
        context.SaveChanges();
    }

Answer 1

after using this implementation of the DataContractSerializer, I got an expected output. as i mentioned in a comment above, the client class is an abridged version. i'm going to slowly go through my client class uncommenting properties until i find the one that seems to have broken the serializer.

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