dataSet.GetXml() doesn't return xml for null or blank columns

gistfile1.cs

First clone the DataTable, make all columns of type string, replace all null values with string.empty, then call GetXml on a new DataSet.

//First bind XML data in to data set..objDataSet

 DataTable dt = objDataSet.Tables[0];
 DataTable dtCloned = dt.Clone();
        foreach (DataColumn dc in dtCloned.Columns)
            dc.DataType = typeof(string);
        foreach (DataRow row in dt.Rows)
        {
            dtCloned.ImportRow(row);
        }

        foreach (DataRow row in dtCloned.Rows)
        {
            for (int i = 0; i < dtCloned.Columns.Count; i++)
            {
                dtCloned.Columns[i].ReadOnly = false;

                if (string.IsNullOrEmpty(row[i].ToString()))
                    row[i] = string.Empty;
            }
        }

        DataSet ds = new DataSet();
        ds.Tables.Add(dtCloned);
        string xml = ds.GetXml();