using System.Xml.Linq

using System.Xml.Linq;
protected void Button1_Click(object sender, EventArgs e)
{
  XDocument doc = new XDocument();
  XElement projectElement = new XElement("Project"
     , new XAttribute("ProjectName", "xxx")
     , new XAttribute("ProjectDescription", "xxx")
     , new XAttribute("DateStart", "xxx")
     , new XAttribute("DateEnd", "xxx") );
  doc.Add(projectElement);
  for (int i = 0; i < 5; i++)
  {
    projectElement.Add(new XElement("Property"
      , new XAttribute("PropertyName", "PropertyName" + i)
      , new XAttribute("PropertyValue", "PropertyValue" + i) ));
  }
  this.lbl.Text = Server.HtmlEncode(doc.ToString());
  this.lbl.DataBind();
}

will produce xml that looks like this

<Project ProjectName="xxx" ProjectDescription="xxx" DateStart="xxx" DateEnd="xxx" >
  <Property PropertyName="PropertyName0" PropertyValue="PropertyValue0" />
  <Property PropertyName="PropertyName1" PropertyValue="PropertyValue1" />
  <Property PropertyName="PropertyName2" PropertyValue="PropertyValue2" />
  <Property PropertyName="PropertyName3" PropertyValue="PropertyValue3" />
  <Property PropertyName="PropertyName4" PropertyValue="PropertyValue4" />
</Project>