从infopath模板创建表单

我已经通过编程方式从模板(xsn)创建了xml文件(infopath表单)。我从模板文件(xsn)中获得了以下xml文件结构。现在我要向xml文件追加值。

   <my:PropertyDetails>
    <my:AddressSelectionList>2201.00000000000</my:AddressSelectionList>
    <my:PropRef>210</my:PropRef>
    <my:UPRN>2201.00000000000</my:UPRN>
    <my:AddressLine>220 test road</my:AddressLine>
    <my:PropId>210</my:PropId>
    <my:BlockUPRN></my:BlockUPRN>
    <my:Attachments xsi:nil="true"></my:Attachments>
    <my:Filegroup>
      <my:URL></my:URL>
      <my:URLText></my:URLText>
    </my:Filegroup>
  </my:PropertyDetails>
  <my:ScaffoldMeasure>
    <my:groupRepeat>
      <my:Description></my:Description>
      <my:Code></my:Code>
      <my:Unit></my:Unit>
      <my:Rate xsi:nil="true"></my:Rate>
      <my:Quantity></my:Quantity>
      <my:Cost xsi:nil="true"></my:Cost>
      <my:Comments></my:Comments>
      <my:ID></my:ID>
      <my:Title></my:Title>
    </my:groupRepeat>
  </my:ScaffoldMeasure>
<my:PorchBalcony>
    <my:groupRepeat>
      <my:Description></my:Description>
      <my:Code></my:Code>
      <my:Unit></my:Unit>
      <my:Rate xsi:nil="true"></my:Rate>
      <my:Quantity></my:Quantity>
      <my:Cost xsi:nil="true"></my:Cost>
      <my:Comments></my:Comments>
      <my:ID></my:ID>
      <my:Title></my:Title>
    </my:groupRepeat>
  </my:PorchBalcony>

我正在尝试访问以下内容:

> XmlNodeList properNodeList =
> xmlDoc.GetElementsByTagName("my:PropertyDetails");
> XmlNodeList smNodeList = xmlDoc.GetElementsByTagName("my:ScaffoldMeasure");
var a=  new XElement(
                myns + "groupRepeat",
                from c in xmlDoc.Elements(nsm + "ScaffoldMeasure") select 
                new XElement(nsm + "groupRepeat",
       new XElement(nsm + "Description", "scaffold1"),
                new XElement(nsm + "Code", "sc1"),
                new XElement(nsm + "Unit", "sc1"),
                new XElement(nsm + "Rate", "sc1"),
                new XElement(nsm + "Quantity", "sc1"),
                new XElement(nsm + "Cost", "sc1"),
                new XElement(nsm + "Comments", "sc1"),
                new XElement(nsm + "ID", "sc1"),
                new XElement(nsm + "Title", "ssssssss")));         
       xmlDoc.Save(@"C:'ttt.xml");

现在我需要在groupreat部分添加值。有人能建议什么是最好的方式追加值的部分?
由于

.....
XNamespace xsi = "http://www.w3.org/2001/XMLSchema-instance";
var sm = xmlDoc.Descendants(nsm + "ScaffoldMeasure").First();
var groupRepeat = new XElement(nsm + "groupRepeat",
                       new XElement(nsm + "Description", "scaffold1"),
                       new XElement(nsm + "Code", "sc1"),
                       new XElement(nsm + "Unit", "sc1"),
                       new XElement(nsm + "Rate", "sc1", 
                                        new XAttribute(xsi + "nil", true)),
                       new XElement(nsm + "Quantity", "sc1"),
                       new XElement(nsm + "Cost", "sc1", 
                                        new XAttribute(xsi + "nil", true)),
                       new XElement(nsm + "Comments", "sc1"),
                       new XElement(nsm + "ID", "sc1"),
                       new XElement(nsm + "Title", "ssssssss"));
sm.Add(groupRepeat);
xmlDoc.Save(@"C:'ttt.xml");