Entity Framework: Missing related objects on client side

Question

I've a (wcf data services) serviceoperation on server side:

<WebGet()> _
Public Function GetProjectsToAdmin() As IQueryable(Of Project)
    Dim ctx As SilverProjectEntities = Me.CurrentDataSource

    Dim query = From p In ctx.Project
                From u In p.Administrators
                Where u.UserID = HttpContext.Current.User.Identity.Name
                Select p

    Return query
End Function

A breakpoint at the line "Return query" shows that the project entities contain all related entities of administrators. But the silverlight client only receives the project entities without the administrator entites. Here is the client code:

Private Sub LoadProjectCompleted(ByVal result As IAsyncResult)
    Dim dsr As DataServiceResponse
    Try
        dsr = ctx.EndExecuteBatch(result)
        For Each resp As QueryOperationResponse In dsr

            If resp.Error IsNot Nothing Then Throw resp.Error

            If result.AsyncState = 0 AndAlso TypeOf resp Is QueryOperationResponse(Of Project) Then
                ReferenceProject.ItemsSource = CType(resp, QueryOperationResponse(Of Project))

            End If
        Next

    Catch ex As Exception
        MessageBox.Show(ex.Message.ToString)
    End Try
End Sub

What is wrong with my code?