Code:

					<Identificacion>
						<Tipo_Personalidad>1</Tipo_Personalidad>
						<Nombre>NOMBRE FUNCIONARIO</Nombre>
						<Apellidos>APELLIDOS FUNCIONARIO</Apellidos>
						<Identificador_Administrativo>
							<Tipo>3</Tipo>
							<Numero_Documento>99999999L</Numero_Documento>
						</Identificador_Administrativo>
					</Identificacion>

And my code

Code:
        Dim tramite As New Tramites
        tramite.LoadByPrimaryKey(1)
        Dim adminXML As XDocument = XDocument.Load("C:\test\propiedad.xml")

     
        Dim ident = From id In adminXML...<Identificacion> _
                   Select New Funcionario With {.Nombre = id...<Nombre>.Value, _
                    .Apellidos = id...<Apellidos>.Value, _
                    .Nif = id...<Numero_Documento>.Value}


        For Each Item As Funcionario In ident
            Dim funcion As Funcionario = tramite.FuncionarioCollectionByTramitesId.AddNew
            'This works, but it's not very elegant
            funcion.Apellidos = Item.Apellidos
            funcion.Nif = Item.Nif
            funcion.Nombre = Item.Nombre
            '...
            'and so on... More than 100 fields in real life
            

            'This (what I want) does not work
            funcion = Item
            'The ES object 'funcion' is filled with the values from
            ' 'Item' but only writes NULLs to the database.

        Next
        tramite.Save()

Code:

        For Each Item As Funcionario In ident
            Item.TramitesId = 1
            tramite.FuncionarioCollectionByTramitesId.AttachEntity(Item)
        Next
        tramite.Save()