WCF Linq to SQL Table - System.Data.Linq.Table cannot be serialized.

Question

I can't figure this out as I go through demos that seem to work. I have a WCF service I was trying to use Linq to SQL with. However, all I ever get is the error System.Data.Linq.Table cannot be serialized. So I started with my own class thinking I could build it back up until get the error. Problem is I get the error even trying to use an empty class. Just using the "As System.Linq.Table(Of xxx)" on my method gives me this error.

Type 'System.Data.Linq.Table`1[LinqADMRequest2b]' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. See the Microsoft .NET Framework documentation for other supported types.

Imports System.ServiceModel
Imports System.ServiceModel.Activation
Imports System.Runtime.Serialization
Imports System.Collections.Generic
Imports Linq

<ServiceContract(Namespace:="")> _
<ServiceBehavior(IncludeExceptionDetailInFaults:=True)> _
<AspNetCompatibilityRequirements(RequirementsMode:=AspNetCompatibilityRequirementsMode.Allowed)> _
Public Class ComplyTrackWCFService

     _
    Public Function GetTestRequests() As System.Data.Linq.Table(Of LinqADMRequest2b)
        'Dim ct As New Linq2.ComplyTrackDataContext()
        'Dim queryresults = ct.ADMRequests 'ct.ADMRequestGetListByUser("", "155")
        'Return queryresults
    End Function

End Class

<DataContract()> _
<Serializable()> _
Public Class LinqADMRequest2b
    Implements ISerializable

    Private _firstName As String
     _
    Public Property FirstName() As String
        Get
            Return _firstName
        End Get
        Set(ByVal Value As String)
            _firstName = Value
        End Set
    End Property

    Public Sub GetObjectData(ByVal info As System.Runtime.Serialization.SerializationInfo, ByVal context As System.Runtime.Serialization.StreamingContext) Implements System.Runtime.Serialization.ISerializable.GetObjectData

    End Sub

End Class

As you can see the GetTestRequests() doesn't do anything other then say it's going to return a System.Data.Linq.Table(Of LinqADMRequest2b)

I can't get the LinqADMRequest2b to serialize.

Type 'System.Data.Linq.Table`1[LinqADMRequest2b]' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. See the Microsoft .NET Framework documentation for other supported types.

Answer 1

Don't return Table<T> from your service. It's a complex queryable type that depends on its DataContext and isn't an in-memory collection.

Do return List<T>, you can convert the Table<T> to a List<T> by calling System.Linq.Enumerable.ToList().

Answer 2

Try putting

<DataMember> attribute on your properties of you own class.

Also, it's better to create lightweight DataContract object to pass down the line rather than big bulky dude like the linq table.