After following what you said, I believe this is something like this:

        ' Convert a DataSet into an Xml
        ' This functions make it so the schema is included
        ' expO1 DataSet
        Public Function DataSetToXml(ByVal toDataSet As DataSet) As String
            Dim loStringWriter As StringWriter = New StringWriter()
            toDataSet.WriteXml(loStringWriter, XmlWriteMode.WriteSchema)
            Return loStringWriter.ToString
        End Function

Can you confirm me if this is pretty much the simpler way to achieve this?

When I call this method, I need to end up with a string. Using StringWriter instead should eliminate the memory problem. Is it?