Datacontract exception. Cannot be serialized

Question

I have the following WCF DataContract:

[DataContract]
public class Occupant
{
    private string _Name;
    private string _Email;
    private string _Organization;
    private string _Badge;

    public Occupant(string name, string badge, string organization)
    {
        Name = name;
        Badge = badge;
        Organization = organization;
    }

    public Occupant(string name, string badge)
    {
        Value = name;
        Key = badge;
    }

    [DataMember]
    public string Key
    {
        get { return _Name; }
        set { _Name = value; }
    }

    [DataMember]
    public string Value
    {
        get { return _Badge; }
        set { _Badge = value; }
    }

    [DataMember]
    public string Name
    {
        get { return _Name; }
        set { _Name = value; }
    }

    [DataMember]
    public string Email
    {
        get { return _Email; }
        set { _Email = value; }
    }

    [DataMember]
    public string Organization
    {
        get { return _Organization; }
        set { _Organization = value; }
    }

    [DataMember]
    public string Badge
    {
        get { return _Badge; }
        set { _Badge = value; }
    }
}

When I try to access this service via web browser (it is hosted on IIS), I am getting this error:

System.Runtime.Serialization.InvalidDataContractException: Type 'MyNamespace.Occupant' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. If the type is a collection, consider marking it with the CollectionDataContractAttribute.

One of my methods is returning a List of type Occupant. Would this be causing it?

Answer 1

Because you have provided one or more initializing constructors, you will also need to add a parameterless (default) constructor.

i.e. You need to add:

[DataContract]
public class Occupant
{
    // *** Needed only for Serialization
    public Occupant() {}
    ...

This is because the default constructor disappears when you add an explicit constructor.

[The issue isn't with the method returning List<Occupant>, since methods aren't serialized).]