Converting a dataset to an xmldata format

public static string ConvertToXML(DataSet ds)
        {
            int rows = ds.Tables[0].Rows.Count;
            int columns = ds.Tables[0].Columns.Count;
            int i = 0;
            string result = "";
            result = "<Rows>";
            for (i = 0; i < rows; i++)
            {
                result = result + "<Row>";
                for (int j = 0; j < columns; j++)
                {
                    result = result + "<Column>" + ds.Tables[0].Rows[i][j].ToString() + "</Column>";
                }
                result = result + "</Row>";
            }
            result = result + "</Rows>";
            return result;
        }