问DataSet.WriteToXml中缺少根命名空间

EN

DataSet ds = new DataSet();
using (SqlConnection connection = new SqlConnection("some connection string"))
using (SqlCommand command = new SqlCommand("select * from mytable", connection))
using (SqlDataAdapter adapter = new SqlDataAdapter(command))
{
    adapter.Fill(ds);
}

XmlDocument xml = new XmlDocument();
using (Stream stream = new MemoryStream())
{
    ds.WriteXml(stream);
    // We must reposition the memory stream before loading the xml
    stream.Position = 0;
    xml.Load(stream);
}