Reporting Services keeps erasing my dataset parameters

<Query>
   <Method Namespace="http://www.abc.com/" Name="TWRPerformanceSummary"/>
   <SoapAction>http://www.abc.com/TWRPerformanceSummary</SoapAction>
       <ElementPath IgnoreNamespaces="true">
            TWRPerformanceSummaryResponse/TWRPerformanceSummaryResult/diffgram/NewDataSet/table{StockPerc,RiskBudget,Custodian,ProductName,StartValue(decimal),EndValue(decimal),CostBasis(decimal)}
       </ElementPath>
</Query>

Guid passedGuid = new Guid(sessionID);

private static void addDummyRow(DataTable dt) {
        var row = dt.NewRow();

        for (int i = 0; i < dt.Columns.Count; i++) {
            if (dt.Columns[i].DataType == typeof(string)) {
                row[i] = dt.Columns[i].ColumnName;
            }
            else if (dt.Columns[i].DataType == typeof(DateTime)) {
                row[i] = new DateTime(1900, 1, 1);
            }
            else {
                row[i] = 0;
            }
        }

        dt.Rows.Add(row);
    }